Although age-related decline in cognitive performance is undeniable, there are two important caveats to this statement. First, most cognitive deficits that have been observed in nondemented older adults are typically limited to certain types of cognitive tasks. In particular, deficits have usually been seen on tasks that required problem-solving [50, 51], speed response on information processing [52], relied on executive processing [53], assessed a variety of types of memory [54], or assessed the acquisition and retention of novel skills [55]. The variability in cognitive decline that occurs with age has provided insights into the areas of the brain that are implicated in ageing, and this can help identify potential mediators of the relationship. Nondemented older adults are typically able to maintain their long-term memory and the ability to perform tasks that are considered to be less effortful regarding attentional demands [56, 57].

The second caveat regarding age-related declines in cognition is that there has been shown to be substantial variability in the rate of decline with age, and, that this process is extremely heterogeneous given that some older adults never experienced declines in their mental abilities. This achievement could be considered successful cognitive ageing, which has also been described as the evasion of disease and disability, continued engagement in social and productive activities, and sustained cognitive and physical functioning [58, 59]. The question why some people are affected more by ageing process than others remains unclear to date, but it is likely that there are certain genetic variants and clinical conditions that could potentially increase the risk of cognitive impairment. Over the past decade, several risk factors such as the e4 allele of the Apolipoprotein E gene, CVD, stroke, hypertension, diabetes, the metabolic syndrome, hypercholesterolemia, arterial fibrillation, smoking and atherosclerosis have been identified as predictive of increased cognitive decline and a higher risk of dementia [60–66].

Given the increase in the size of the population of older adults and the personal and social consequences of age-related cognitive decline, research related to the maintenance of cognitive functioning is of increasing relevance. From an environmental perspective, promoting healthy adult lifestyle behaviours may attenuate harmful effects of less modifiable risk factors. Therefore, identifying genetic and lifestyle factors which predict successful ageing represents an important direction for researchers in delineating the risk factors for cognitive decline and developing behavioural interventions designed to attenuate cognitive decline.

lifestyle factors may lessen an individual's risk of developing cognitive decline. The evidence of a correlation was strongest in the case of an increase in an individual's level of physical activity, followed by cessation of smoking. These interventions carry few risks and have many additional health benefits, so can be recommended for most of the older population. Other factors such as increasing social engagement, cognitive stimulation and homocysteine-lowering vitamin supplements also appear promising, with considerable observational evidence supporting their uptake, although there is still a lack of empirical evidence for these interventions [73]. Similarly, fitness training interventions were found to have robust but selective benefits for cognition, with the largest fitness-induced benefits occurring for executive-control processes [86]. This indicates that cognitive and neural plasticity could be maintained throughout the lifespan. However, the real risk of dementia is probably underestimated, and it is not clear how many people quit smoking between the time of the initial survey and the onset of

Cognitive Ageing

55

http://dx.doi.org/10.5772/intechopen.79119

Research has also shown that diet can help prevent, better manage or even reverse conditions such as hypertension, hyperlipidemia (high cholesterol), hyperglycemia (high blood sugar) and atherosclerosis that may lead to cardiovascular and cerebrovascular disease. In turn, this affects optimal functioning of organs including the brain due to inefficient transfer of glucose and oxygen necessary for optimal neuronal transfer, with a significant impact on cognitive functioning. To current date, only limited work has investigated the combined effect of these behaviours in relation to cognitive outcomes, and when this evidence exists, findings are inconsistent. For example, a French study investigating alcohol (wine consumption) and smoking in 833 older adults from the Eugeria longitudinal study of cognitive ageing showed that there was no apparent protection from these combined behaviours against Alzheimer's disease. For instance, smoking was associated with an increased decline in language performance even when adjusted for wine consumption, and the latter was associated with an increased decline in attention and memory while adjusting for smoking [87]. The study cites previous evidence, however, suggesting that only smoking (using a pack-years measure) was significantly related to declining in digit span, while low-to-moderate alcohol consumption was not significantly

More recent work has highlighted that the number, duration, and the interaction between some unhealthy behaviours were all associated with subsequent cognition in later life. In a study of London civil servants (Whitehall II cohort) the interaction between alcohol and smoking was investigated, and these results highlighted that the combined effects of smoking and alcohol consumption were greater than the individual effects. Participants who were smokers and drank heavily experienced a 36% faster cognitive decline compared to non-smokers who drank in moderation. These associations were maintained after adjusting for age, sex, educa-

A previous investigation conducted in the same cohort highlighted that participants with three to four unhealthy behaviours were more likely to have poor executive function and memory, compared to those with no unhealthy behaviours. Also, the odds of lower cognitive function were higher when the number of unhealthy behaviours was repeated over time (across three different waves) [89]. Similar findings from the Suwon Longitudinal Ageing Study (SLAS) showed that a combination of multiple positive lifestyle behaviours (such as non-smoking,

dementia, but there were clear long-term consequences of mid-life smoking.

associated to a subsequent three-year change in performance.

tion and chronic diseases [88].

## **5. The role of lifestyle behaviours on cognitive ageing**

Lifestyle behaviours refer to routine activities (e.g. smoking, alcohol, diet and physical activity) that could influence our health. Because of their impact on various health outcomes, the term "lifestyle behaviours" has also been referred to as "health-related behaviours". Many studies have shown that lifestyle behaviours are associated with type 2 diabetes [67, 68], coronary heart disease [69] and mortality [70]. An example is a recent study that followed a cohort of more than 20,000 people aged 45 to 79 living in the Norfolk area in the United Kingdom between 1993 and 1997, which investigated the association between lifestyle behaviours and mortality [71]. The results of this study showed that people who smoked, drank more than 14 units of alcohol per week, consumed fewer than five servings of fruit and vegetables per day, and were inactive, had a four-times higher mortality risk than those who exhibited none of these lifestyle behaviours. An important aspect that needs further highlighting is that lifestyle behaviours are not always independent of one another, and may also have additive effects on various health outcomes.

Optimal control and management of lifestyle factors demonstrate efficacy in the prevention of cognitive decline and dementia [72–75], highlighting an intertwined link between the risk factors for cardiovascular and cerebrovascular disease and dementia. Accumulating evidence points to the potential risk factors of cardiovascular disorders (e.g. midlife obesity and cigarette smoking) and the potential protective roles of psychosocial and lifestyle factors (e.g. higher education, regular exercise, healthy diet, intellectually challenging leisure activities, and an active socially integrated lifestyle).

Factors showing a considerable influence on decreasing the risk of dementia and cognitive decline are social and cognitive engagement. Other influences such as physical activity, which increases cerebral blood flow and in turn promotes nerve cell growth and enhanced cerebrovascular function, seem to be the most frequently cited lifestyle in the cognitive ageing literature. However, it is highly probable that physical activity may also enhance cognition through other mediator factors such as depression, sleep, appetite (diet), and energy levels by postponing or preventing age-related diseases (e.g. diabetes, hypertension) known to affect cognition. Furthermore, there were also well-known documented benefits of non-smoking [76–78], moderate alcohol consumption [8, 79–82] and healthy dietary choices [78, 83–85] for a healthy and successful cognitive functioning from mid to later life.

In addition to considerable observational data of the independent effects of lifestyle factors, there is now increasing empirical evidence from intervention studies [73], that alterations in lifestyle factors may lessen an individual's risk of developing cognitive decline. The evidence of a correlation was strongest in the case of an increase in an individual's level of physical activity, followed by cessation of smoking. These interventions carry few risks and have many additional health benefits, so can be recommended for most of the older population. Other factors such as increasing social engagement, cognitive stimulation and homocysteine-lowering vitamin supplements also appear promising, with considerable observational evidence supporting their uptake, although there is still a lack of empirical evidence for these interventions [73]. Similarly, fitness training interventions were found to have robust but selective benefits for cognition, with the largest fitness-induced benefits occurring for executive-control processes [86]. This indicates that cognitive and neural plasticity could be maintained throughout the lifespan. However, the real risk of dementia is probably underestimated, and it is not clear how many people quit smoking between the time of the initial survey and the onset of dementia, but there were clear long-term consequences of mid-life smoking.

Given the increase in the size of the population of older adults and the personal and social consequences of age-related cognitive decline, research related to the maintenance of cognitive functioning is of increasing relevance. From an environmental perspective, promoting healthy adult lifestyle behaviours may attenuate harmful effects of less modifiable risk factors. Therefore, identifying genetic and lifestyle factors which predict successful ageing represents an important direction for researchers in delineating the risk factors for cognitive decline and

Lifestyle behaviours refer to routine activities (e.g. smoking, alcohol, diet and physical activity) that could influence our health. Because of their impact on various health outcomes, the term "lifestyle behaviours" has also been referred to as "health-related behaviours". Many studies have shown that lifestyle behaviours are associated with type 2 diabetes [67, 68], coronary heart disease [69] and mortality [70]. An example is a recent study that followed a cohort of more than 20,000 people aged 45 to 79 living in the Norfolk area in the United Kingdom between 1993 and 1997, which investigated the association between lifestyle behaviours and mortality [71]. The results of this study showed that people who smoked, drank more than 14 units of alcohol per week, consumed fewer than five servings of fruit and vegetables per day, and were inactive, had a four-times higher mortality risk than those who exhibited none of these lifestyle behaviours. An important aspect that needs further highlighting is that lifestyle behaviours are not always independent of one another, and may also have additive

Optimal control and management of lifestyle factors demonstrate efficacy in the prevention of cognitive decline and dementia [72–75], highlighting an intertwined link between the risk factors for cardiovascular and cerebrovascular disease and dementia. Accumulating evidence points to the potential risk factors of cardiovascular disorders (e.g. midlife obesity and cigarette smoking) and the potential protective roles of psychosocial and lifestyle factors (e.g. higher education, regular exercise, healthy diet, intellectually challenging leisure activities,

Factors showing a considerable influence on decreasing the risk of dementia and cognitive decline are social and cognitive engagement. Other influences such as physical activity, which increases cerebral blood flow and in turn promotes nerve cell growth and enhanced cerebrovascular function, seem to be the most frequently cited lifestyle in the cognitive ageing literature. However, it is highly probable that physical activity may also enhance cognition through other mediator factors such as depression, sleep, appetite (diet), and energy levels by postponing or preventing age-related diseases (e.g. diabetes, hypertension) known to affect cognition. Furthermore, there were also well-known documented benefits of non-smoking [76–78], moderate alcohol consumption [8, 79–82] and healthy dietary choices [78, 83–85] for

In addition to considerable observational data of the independent effects of lifestyle factors, there is now increasing empirical evidence from intervention studies [73], that alterations in

a healthy and successful cognitive functioning from mid to later life.

developing behavioural interventions designed to attenuate cognitive decline.

**5. The role of lifestyle behaviours on cognitive ageing**

effects on various health outcomes.

54 Geriatrics Health

and an active socially integrated lifestyle).

Research has also shown that diet can help prevent, better manage or even reverse conditions such as hypertension, hyperlipidemia (high cholesterol), hyperglycemia (high blood sugar) and atherosclerosis that may lead to cardiovascular and cerebrovascular disease. In turn, this affects optimal functioning of organs including the brain due to inefficient transfer of glucose and oxygen necessary for optimal neuronal transfer, with a significant impact on cognitive functioning.

To current date, only limited work has investigated the combined effect of these behaviours in relation to cognitive outcomes, and when this evidence exists, findings are inconsistent. For example, a French study investigating alcohol (wine consumption) and smoking in 833 older adults from the Eugeria longitudinal study of cognitive ageing showed that there was no apparent protection from these combined behaviours against Alzheimer's disease. For instance, smoking was associated with an increased decline in language performance even when adjusted for wine consumption, and the latter was associated with an increased decline in attention and memory while adjusting for smoking [87]. The study cites previous evidence, however, suggesting that only smoking (using a pack-years measure) was significantly related to declining in digit span, while low-to-moderate alcohol consumption was not significantly associated to a subsequent three-year change in performance.

More recent work has highlighted that the number, duration, and the interaction between some unhealthy behaviours were all associated with subsequent cognition in later life. In a study of London civil servants (Whitehall II cohort) the interaction between alcohol and smoking was investigated, and these results highlighted that the combined effects of smoking and alcohol consumption were greater than the individual effects. Participants who were smokers and drank heavily experienced a 36% faster cognitive decline compared to non-smokers who drank in moderation. These associations were maintained after adjusting for age, sex, education and chronic diseases [88].

A previous investigation conducted in the same cohort highlighted that participants with three to four unhealthy behaviours were more likely to have poor executive function and memory, compared to those with no unhealthy behaviours. Also, the odds of lower cognitive function were higher when the number of unhealthy behaviours was repeated over time (across three different waves) [89]. Similar findings from the Suwon Longitudinal Ageing Study (SLAS) showed that a combination of multiple positive lifestyle behaviours (such as non-smoking, vegetable consumption and social activity) was associated with the higher cognitive ability [90]. However, since these behaviours tend to cluster [91, 92], the extent to which apparent effects of one behaviour were attributable to (i.e. confounded by) another is uncertain.

that the highest level of midlife physical activity was associated with better memory (but not search speed) at baseline, and a consistently healthy dietary choice was associated with slower memory decline from mid to later life. In addition, the highest level of physical activity at age 43 and across early midlife was associated with slower visual search speed decline, independently of every other lifestyle behaviour and of selected covariates: social class of origin, childhood cognition, educational attainment, adult social class, symptoms of anxiety and depression, and clinical conditions (hypertension, diabetes, cancer, CVD) and frailty. Smoking was not associated with either cognitive outcome, but since the number of heavy smokers was relatively low in this sample, these conclusions should be interpreted with caution. It should also be noted that their findings for dietary choice and physical activity were not always con-

Cognitive Ageing

57

http://dx.doi.org/10.5772/intechopen.79119

sistent at different ages across midlife, compared to effects of the cumulative scores.

the present study).

of dementia prevention.

The associations between physical activity and a slower decline in visual search speed in Cadar's study, and between healthy dietary choice and memory, are new findings and were not previously tested on this cohort. In the former case, physical activity was not investigated in relation to search speed in the previous study; in the latter case, midlife cognition has not previously been studied in relation to diet on this cohort. On the other hand, the associations between heavy smoking at age 43 and faster memory decline previously reported between ages 43 and 53 (Richards et al., 2003) were not replicated here with the 20-year period of cognitive change from 43 to 60+ years. The loss of the cumulative midlife heavy smoking-memory decline association may be due to low statistical power resulting from the relatively high odds of morbidity and premature mortality in this sub-group (135 study members smoking more than 20 cigarettes per day at age 43 were represented in the previous study, compared to 22 in

Evidence from a study of London civil servants found an effect of sex on the association between smoking and cognitive decline in a study of London civil servants. Their results showed that men who smoked showed faster decline than non-smoking men over a 10-year period, after adjusting for the effects of heart disease, stroke and lung function on mental abilities, while for women there were no differences in cognitive scores over the same period. This could be related to the lower number of female participants as compared to males in the Whitehall II study [105]. In relation to physical activity, leisure-time physical activity at least twice a week in midlife was associated with reduced risk of memory decline in the Cardiovascular risk factors, Ageing and Incidence of Dementia (CAIDE) study, after adjustment for age, sex, education, follow-up time, locomotor disorders, APOE genotype, vascular disorders, smoking, and alcohol consumption [106]. Similarly, in The Mayo Clinic Study of Ageing moderate exercise in midlife or late life was associated with reduced odds of Mild Cognitive Impairment (MCI) [107]. In contrast, results from the Chicago Health and Ageing Project reported that physical activity conducted within 2 weeks of the date of baseline cognitive assessment was not associated with risk of cognitive decline in an older population [108]. Given that lifestyle behaviours are modifiable risk factors indicates that encouraging a healthy lifestyle may prevent or ameliorate cognitive decline and underlying cerebrovascular and cardiovascular risk factors [109]. Designing interventions that promote healthy lifestyles should represent key components of any response to the potentially overwhelming problem

Furthermore, relatively little is known about the longitudinal effects of these behaviours on the cognitive decline; yet associations among multiple lifestyle behaviours emphasise longitudinal studies since patterns of behaviours tend to develop over decades, with implications for targeted interventions to change the aggregate public health risk [93]. The life course approach to age-related diseases [94, 95] provides an important opportunity to identify the nature and timing of different environmental contributions to neuronal damage and the risk of dementia across life [96].

Risk and protective factors for health can exert their most critical influences at different ages [97]. This was acknowledged by the life course approach and the hypothesis that positive lifestyle behaviours such as non-smoking, being physically active and choosing healthier diets may protect cognitive functioning and a slow cognitive decline in later life. Fratiglioni et al. identified key periods for potential risk and protective factors [97]. Early life seems to be most critical for the development of cognitive reserve (learning and education) [98–100] when distal adverse influences (such as poor childhood social circumstances) contribute to the risk of adult disease or later life risk of dementia. Lifestyle behaviours, including those that influence cardiovascular and metabolic risk, become more influential in midlife, although some, such as diet and physical activity, track back into childhood [101, 102], whereas mental and physical activity patterns may continue to moderate these risks into later life [103, 104] (see **Figure 3**).

Cadar et al. examined the associations between lifestyle behaviours in early midlife (36 and 43 years) independently of each other, and in combination, in relation to cognitive performance at age 43, and cognitive decline over 20 years from 43 to 60–64 using the Medical Research Council 1946 Brtish Birth Cohort [78]. Key findings for the former analyses were

**Figure 3.** A life course timeline presenting the risk and protective factors across the life course.

that the highest level of midlife physical activity was associated with better memory (but not search speed) at baseline, and a consistently healthy dietary choice was associated with slower memory decline from mid to later life. In addition, the highest level of physical activity at age 43 and across early midlife was associated with slower visual search speed decline, independently of every other lifestyle behaviour and of selected covariates: social class of origin, childhood cognition, educational attainment, adult social class, symptoms of anxiety and depression, and clinical conditions (hypertension, diabetes, cancer, CVD) and frailty. Smoking was not associated with either cognitive outcome, but since the number of heavy smokers was relatively low in this sample, these conclusions should be interpreted with caution. It should also be noted that their findings for dietary choice and physical activity were not always consistent at different ages across midlife, compared to effects of the cumulative scores.

The associations between physical activity and a slower decline in visual search speed in Cadar's study, and between healthy dietary choice and memory, are new findings and were not previously tested on this cohort. In the former case, physical activity was not investigated in relation to search speed in the previous study; in the latter case, midlife cognition has not previously been studied in relation to diet on this cohort. On the other hand, the associations between heavy smoking at age 43 and faster memory decline previously reported between ages 43 and 53 (Richards et al., 2003) were not replicated here with the 20-year period of cognitive change from 43 to 60+ years. The loss of the cumulative midlife heavy smoking-memory decline association may be due to low statistical power resulting from the relatively high odds of morbidity and premature mortality in this sub-group (135 study members smoking more than 20 cigarettes per day at age 43 were represented in the previous study, compared to 22 in the present study).

Evidence from a study of London civil servants found an effect of sex on the association between smoking and cognitive decline in a study of London civil servants. Their results showed that men who smoked showed faster decline than non-smoking men over a 10-year period, after adjusting for the effects of heart disease, stroke and lung function on mental abilities, while for women there were no differences in cognitive scores over the same period. This could be related to the lower number of female participants as compared to males in the Whitehall II study [105]. In relation to physical activity, leisure-time physical activity at least twice a week in midlife was associated with reduced risk of memory decline in the Cardiovascular risk factors, Ageing and Incidence of Dementia (CAIDE) study, after adjustment for age, sex, education, follow-up time, locomotor disorders, APOE genotype, vascular disorders, smoking, and alcohol consumption [106]. Similarly, in The Mayo Clinic Study of Ageing moderate exercise in midlife or late life was associated with reduced odds of Mild Cognitive Impairment (MCI) [107]. In contrast, results from the Chicago Health and Ageing Project reported that physical activity conducted within 2 weeks of the date of baseline cognitive assessment was not associated with risk of cognitive decline in an older population [108].

Given that lifestyle behaviours are modifiable risk factors indicates that encouraging a healthy lifestyle may prevent or ameliorate cognitive decline and underlying cerebrovascular and cardiovascular risk factors [109]. Designing interventions that promote healthy lifestyles should represent key components of any response to the potentially overwhelming problem of dementia prevention.

**Figure 3.** A life course timeline presenting the risk and protective factors across the life course.

vegetable consumption and social activity) was associated with the higher cognitive ability [90]. However, since these behaviours tend to cluster [91, 92], the extent to which apparent

Furthermore, relatively little is known about the longitudinal effects of these behaviours on the cognitive decline; yet associations among multiple lifestyle behaviours emphasise longitudinal studies since patterns of behaviours tend to develop over decades, with implications for targeted interventions to change the aggregate public health risk [93]. The life course approach to age-related diseases [94, 95] provides an important opportunity to identify the nature and timing of different environmental contributions to neuronal damage and the risk

Risk and protective factors for health can exert their most critical influences at different ages [97]. This was acknowledged by the life course approach and the hypothesis that positive lifestyle behaviours such as non-smoking, being physically active and choosing healthier diets may protect cognitive functioning and a slow cognitive decline in later life. Fratiglioni et al. identified key periods for potential risk and protective factors [97]. Early life seems to be most critical for the development of cognitive reserve (learning and education) [98–100] when distal adverse influences (such as poor childhood social circumstances) contribute to the risk of adult disease or later life risk of dementia. Lifestyle behaviours, including those that influence cardiovascular and metabolic risk, become more influential in midlife, although some, such as diet and physical activity, track back into childhood [101, 102], whereas mental and physical activity patterns may continue to moderate these risks into later life [103, 104] (see **Figure 3**). Cadar et al. examined the associations between lifestyle behaviours in early midlife (36 and 43 years) independently of each other, and in combination, in relation to cognitive performance at age 43, and cognitive decline over 20 years from 43 to 60–64 using the Medical Research Council 1946 Brtish Birth Cohort [78]. Key findings for the former analyses were

effects of one behaviour were attributable to (i.e. confounded by) another is uncertain.

of dementia across life [96].

56 Geriatrics Health

## **6. Policy implications**

Despite major progress in understanding the neurobiology of cognitive impairment and dementia, there are still no clear determinants and complete causal models available for explaining risks for this condition [110]. As noted, the Department of Health National Dementia Strategy acknowledges that "what is good for the heart is also good for the brain". This implies that limited consumption of alcohol, non-smoking, an active physical lifestyle, and a balanced, low-energy-dense/nutrient-rich diet should all contribute to a healthy brain. Cognitive decline itself is a predictor of dementia. Thus, the implied message is that by changing lifestyle behaviours dementia may be delayed or even prevented.

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## **7. Conclusions**

This chapter has presented an overview of the process of cognitive ageing from a life course perspective and discussed the role of lifestyle behaviours on successful cognitive ageing. The evidence presented highlights the important role of lifestyle behaviours (especially physical activity and healthy dietary choices) on maintaining an optimal level in different aspects of cognitive function. Adopting more than one healthy lifestyle behaviour across early midlife seems to be protective against a faster decline in several domains of cognitive functioning, highlighting a dose response with the number of lifestyle behaviours adopted. With an increase in the ageing population, the number of older people affected by cognitive decline and dementia is continually rising, causing a major public health burden on individuals and governments around the world.

## **Acknowledgements**

The work presented was supported by the Medical Research Council (MRC), Economic and Social Research Council (ESRC), and the National Institute on Ageing.

## **Conflict of interest**

The author declares no financial relationships with any organisations that might have an interest in the submitted work; no other relationships or activities that could appear to have influenced the proposed work.

## **Author details**

Dorina Cadar

Address all correspondence to<EMAIL_ADDRESS>
Department of Behavioural Science and Health, University College London, London, UK

## **References**

**6. Policy implications**

58 Geriatrics Health

**7. Conclusions**

**Acknowledgements**

**Conflict of interest**

**Author details**

Dorina Cadar

influenced the proposed work.

Address all correspondence to<EMAIL_ADDRESS>
Despite major progress in understanding the neurobiology of cognitive impairment and dementia, there are still no clear determinants and complete causal models available for explaining risks for this condition [110]. As noted, the Department of Health National Dementia Strategy acknowledges that "what is good for the heart is also good for the brain". This implies that limited consumption of alcohol, non-smoking, an active physical lifestyle, and a balanced, low-energy-dense/nutrient-rich diet should all contribute to a healthy brain. Cognitive decline itself is a predictor of dementia. Thus, the implied message is that by chang-

This chapter has presented an overview of the process of cognitive ageing from a life course perspective and discussed the role of lifestyle behaviours on successful cognitive ageing. The evidence presented highlights the important role of lifestyle behaviours (especially physical activity and healthy dietary choices) on maintaining an optimal level in different aspects of cognitive function. Adopting more than one healthy lifestyle behaviour across early midlife seems to be protective against a faster decline in several domains of cognitive functioning, highlighting a dose response with the number of lifestyle behaviours adopted. With an increase in the ageing population, the number of older people affected by cognitive decline and dementia is continually rising, causing a major public health burden on individuals and governments around the world.

The work presented was supported by the Medical Research Council (MRC), Economic and

The author declares no financial relationships with any organisations that might have an interest in the submitted work; no other relationships or activities that could appear to have

Department of Behavioural Science and Health, University College London, London, UK

Social Research Council (ESRC), and the National Institute on Ageing.

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## *Edited by Hülya Çakmur*

Aging is characterized by functional decline in every organ due to several cellular, biological, and physiological changes over time. Molecular and cellular damages are gradually decreasing in the physical and mental capacities of the human body. Health results have shown that lifespan has dramatically increased during the twenty-first century. Increasing elderly population naturally deals with many health problems leading to a rise in health expenditure and labor loss. The good news is that the clinical trials in gene therapy have almost stopped and/or reversed human aging. Regenerative medicine can repair and reverse aging in all body cells. Thus, the body's own repair mechanisms may struggle with aging and age-related diseases. Research is promising and suggests that human aging will be eradicated on earth.

Published in London, UK © 2018 IntechOpen © Oskanov / iStock

Geriatrics Health

Geriatrics Health


**13. Discussion**

Sleep doubles as an important component of activity cycle and a restorationdriven physiological state [107, 109, 127]. Inability to sleep or insufficiency of sleep in frontline health workers managing COVID patients is caused by and has been associated with a number of adverse consequences [83]. Anxiety either due to fear of infection or an increase in job demand, hypertension, chronobiological disruption, prolonged exposure to artificial light, and stress are important contributing factors to insomnia experienced by frontline COVID-19 health workers. Sleep disruption

#### **Figure 2.**

*Prolonged light exposure and sleep disorders in frontline health workers during COVID-19. Pineal melatonin becomes suppressed by prolonged exposure to light resulting into disruption of normal circadian sleep.*

in frontline health workers may present a number of ugly consequences including neurocognitive decline. This is due to a number of reasons. The dura mater appears to be involved in the clearance of brain toxins via a novel lymphatic system of neuroglia referred to as the "glymphatic" clearance system. Glymphatic clearance is shown to occur mainly during slow-wave sleep [67]. During slow-wave sleep, brain levels of adenosine, the main metabolite of ATP, and TNF-alpha, a primary pro-inflammatory mediator of immunity, appear to increase; whereas the brain's acetylcholine and monoamines (norepinephrine, dopamine, and serotonin) decrease. Disruption of slow wave sleep experienced by frontline COVID-19 health workers makes it difficult to eliminate brain toxins and increases the risk of diseases including sleep disorders.

Anxiety in frontline COVID-19 health workers is another concern. Generally, anxiety is characterized by sympathetic activation. Increased expression of Cannabinoid type-1 (CB1) receptors owing to activation of the sympathetic nervous system has been documented [87]. CB1 receptors are expressed in the brain where they modulate GABA release culminating in sleep deprivation. Moreover, decline in basal forebrain brain derived neurotrophic factor (BDNF) and adenosine and a rise in nitric oxide in animal models have been linked with emotional disorder-related alteration in sleep pattern [89]. Hippocampus, a birthplace of theta waves, plays an important role during sleep. Depletion of hippocampal glycogen and attendant alteration in EEG waves may atone for sleep disruption that characterizes COVID-19 frontline health workers [92]. CRH is released during stress and anxiety and this hormone has been shown to depress NREM waves in C57BL/67 and CRH-R1 CL mice [97]. Spontaneous reticular thalamic discharges, implicated in synchronizing NREM waves, are known to suppress cortical activation by peripheral stimuli. Disruption of sleep occasioned by Inhibition of spontaneous reticular thalamic discharge has been reported following CRH injection [94].

Spontaneous discharge of noradrenergic fibers during basal state may explain how hypertension causes insomnia in frontline COVID-19 healthcare workers [104]. Disruption of normal secretory rhythm of hormones and chemical messengers and presence of circadian genes such as CLOCK rs1801260 locus bearing TC and CLOCK *Occupational Stress-Related Sleep Anomaly in Frontline COVID-19 Health Workers… DOI: http://dx.doi.org/10.5772/intechopen.109148*

rs680524 bearing GC and CC may contribute in substantive level to sleep disruption in frontline COVID-19 health workers. At least, studies have indicated an alteration in the circadian rhythm of leptin in people with sleep deprivation [113]. Changes in the normal secretory rhythm of Gamma Amino Butyric Acid (GABA) have also been implicated in sleep abnormality [118]. Like circadian disruption, prolonged exposure to ambient light may increase sleep latency. Light is known to suppress nocturnal melatonin synthesis making initiation of sleep difficult. Blue light has been shown to exert the greatest suppressive effect on melatonin secretion [117]. Light-related suppression in melatonin is due to a reduction in postganglionic noradrenergic neural discharge to the pineal gland. The ability of light to suppress melatonin secretion is known as the negative masking effect of light.

In summary, the review highlighted the possible mechanisms that underlie sleep anomaly that characterized frontline COVID-19 workers using existing information from experimental studies. Presence of CLOCK rs1801260 locus bearing TC and CLOCK rs680524 bearing GC and CC and stress-induced elevation of cannabinoid receptors, depletion of adenosine and forebrain derived neurotrophic factor, depletion of hippocampal glycogen and a rise in nitric oxide suppress spontaneous thalamic discharges which are involved in sleep induction are possible underlying mechanisms.

### **14. Conclusion**

COVID-19 emergence and the attendant waves of responses from frontline healthcare officers have been very remarkable. The review has highlighted the possible underlying mechanisms associated with occupational stress-induced sleep disorders in frontline healthcare providers managing COVID-19. It is very glaring from primary studies that COVID-19-induced occupational stress causes sleep disorders most especially insomnia in both male and female frontline healthcare workers which are connectable to a number of underlying factors including anxiety leading to neuroimmunological changes. Anxiety-associated sleep anomaly is attributable to stimulation of the reticular activating system which occurs as a result of activation of noradrenergic fiber and sympatho-adrenal axis.  Spontaneous discharge of noradrenergic fiber during basal state and changes in the normal secretory rhythm of hypnosis-related chemical messengers may be responsible for hypertension- and chronobiological disruption-induced sleep disorders respectively. Lastly, prolonged light exposure-induced suppression of melatonin secretion may elicit disruption of normal circadian sleep.

### **Conflict of interest**

The authors declare no conflict of interest.


**1. Introduction - support of teachers as a COVID-19 emergency**

The pandemic crisis has affected people's lifestyles by inducing countries to change the management of entire sectors of private and public life [1–3]. It is estimated that over 1.58 billion children and young people attending educationtraining courses - around 94% of students worldwide - in 200 countries no longer went to school in March 2020 [1, 4] and that countries have had to adopt various measures to continue students' learning during school closure.

Countries have used a variety of resources to ensure remote learning for students (radio and television); specifically, to ensure online education, recovered instructional resources [5], as online platforms with tools included - educational content for exploring, real-time lessons on virtual meeting platforms, online support services for parents and students, self-paced formalized lessons [6].

Such situation is inevitably leading to the reconfiguration of the entire education system and, above all, to the acceleration of change in teaching-learning processes [7]. The urgent implementation of new ways to deal with the crisis - use of remote teaching, flexibility of schedules and functions, etc. - indeed, made it possible to experiment with 'solutions previously considered difficult or impossible to implement' (p. 4) and to concentrate efforts to address training needs that have always been known but which the pandemic situation has in fact forced to solve - such as, among othersi , support for the teaching profession and the preparation of teachers.

The COVID-19 pandemic and such abrupt modification of teaching delivery accelerated the process of transforming teaching practices, such as remotely supporting students through innovative technological means [7, 8]; such situation asked teachers above all to face new challenges such as that of supporting students remotely through innovative technological means. Since the early pandemic teachers were tasked to implement teaching in distance learning modalities, "often without sufficient guidance, training, or resources" ([7], p. 14). They:

*were largely unprepared to support continuity of learning and adapt to new teaching methodologies (…) Even in contexts with adequate infrastructure and connectivity, many educators lack the most basic ICT skills, meaning they will likely struggle with their own ongoing professional development, let alone with facilitating quality distance learning' ([7], p. 15).*

For this reason, the COVID-19 crisis has highlighted among the many things that in-service teacher training 'are in need of reform to better train teachers in new methods of education delivery' ([7], p. 15).

As already noted by Hattie and by Pitler et al. [9, 10], the current situation has finally made it clear that to support the teaching profession and the preparation of teachers it is not enough to provide them with: 'Technology alone cannot guarantee good learning outcomes. More important than training teachers in ICT skills, is ensuring that they have the assessment and pedagogical skills to meet students at their level and to implement the accelerated curricula and differentiated learning strategies' ([7], p. 23).

As suggested by Anderson [11, 12], in order to avoid the negative effects of the so-called *coronateaching* [13]1 - i.e. the poor quality of the training offer and the ineffectiveness of the production of skills, due to sudden transformation of frontal lessons in virtual mode without investing the curriculum or teaching methodology - the support offered to students by teachers and tutors becomes fundamental, especially through - upstream - the redesign of the course in terms of both the curriculum and strategies, − downstream - the monitoring of students' learning processes.

The specific limit of the emergency adaptation of courses in online mode, in fact, would not be so much in the lack of support offered by teachers to students - in terms of the 'teacher-student' relationship -, but rather in the lack of link between

**21**

**Table 1**.

category (see **Table 2**).

*Remote Support through Technologies: A Research-Training on Teachers' 'Sophisticated Knowledge'*

pedagogical contents, of differentiated learning environments, by means of digital technologies and organization of learning experiences - in terms of the 'teachercourse' relationship -, which involves both the planning of the instructional design

As highlighted by UN ([7], p. 24) 'digital solutions need relevant content, adequate instructional models, effective teaching practices and a supportive learning environment'. It then becomes possible to dispel the *myth* of teaching 'with'

Already in 2019 the TALIS [19] survey revealed the strong need for teacher training in the use of information and communication technologies (ICT) - despite 60% of teachers received professional development in ICT, 18% in fact reported a higher need for development in this area. The preparation of teachers to support students' digital learning is not based only on ICT skills [5]: 'technology does not just change methods of teaching and learning, it can also elevate the role of teachers from imparting received knowledge towards working as co-creators of knowledge,

Teacher training, in general and even more so in the current context, is effective if useful for build pedagogical and technical skills, for integrate digital tools into

While in the early emergency the first generalized response was to provide

OECD [22] stressed in the second study that 'for educators, the COVID-19 pandemic is a quintessence of the adaptive and transformative challenge, for which there is no pre-configured playbook that can guide appropriate responses' ([22], p. 2) and provides a set of online educational resources to support continuity of

1.*Curriculum resources* - as lectures, videos, interactive learning modules;

2.*Professional development resources* - resources to support teachers (or parents) in the ability to teach at a distance, to support learners, more independently at

3.*Tools* - teaching and learning management tools, communication, creation or

The second one resources were assessed on the basis of a specific taxonomy for classifying the curriculum and professional development resources [23], see

2 Applications, platforms and educational resources for use by parents, teachers, school administrators

to support student learning and offer assistance during school closing periods.

Regards resources for professional development suggested by OECD [8], the following table shows the professional skills activated as well as the related taxonomic

 [4] that made it possible to set up a 'field' [21] distance learning, then it was possible to start thinking on the skills needed by the teacher to cope with this

*DOI: http://dx.doi.org/10.5772/intechopen.95949*

(ID) and the choice of learning design - LD [14–16].

**2. (Useful) support to (real) needs of teachers**

as coaches, as mentors and as evaluators' ([5], p. 17).

learning environment [5, 19, 20].

home rather than at school;

access to educational content.

tools2

situation.

teaching and learning:

technologies [17, 18] and put teaching strategies at the center.

1 The neologism is taken from the UNESCO-IESCALC document 'COVID-19 and higher education' [13] in which it is defined as the tendency to 'transform present lessons in a virtual mode, without changing the curriculum or methodology (...) abrupt entry into a complex teaching modality, with multiple technological and pedagogical options and with a steep learning curve (which could involve) frustration and overwhelming adaptation to an educational modality never experienced before without the corresponding training' [13, p. 25].

*Remote Support through Technologies: A Research-Training on Teachers' 'Sophisticated Knowledge' DOI: http://dx.doi.org/10.5772/intechopen.95949*

pedagogical contents, of differentiated learning environments, by means of digital technologies and organization of learning experiences - in terms of the 'teachercourse' relationship -, which involves both the planning of the instructional design (ID) and the choice of learning design - LD [14–16].

As highlighted by UN ([7], p. 24) 'digital solutions need relevant content, adequate instructional models, effective teaching practices and a supportive learning environment'. It then becomes possible to dispel the *myth* of teaching 'with' technologies [17, 18] and put teaching strategies at the center.