Physical activity for the prevention and treatment of major chronic disease: an overview of systematic reviews All in the Family: systematic reviews, rapid reviews, scoping reviews, realist reviews, and more Physical rehabilitation interventions for adult patients with critical illness across the continuum of recovery: an overview of systematic reviews protocol Intrapersonal, social and physical environmental determinants of moderate-to-vigorous physical activity in working-age women: a systematic review protocol Inclusion of quasi-experimental studies in systematic reviews of health systems research. Issues related to the conduct of systematic reviews: a focus on the nutrition field. Replication in Prevention Science Systematic reviews in public health: old chestnuts and new challenges. Overview of Systematic Reviews: Yoga as a Therapeutic Intervention for Adults with Acute and Chronic Health Conditions Decision aids for triage of patients with chest pain: a systematic review of field evaluation studies. ERP indices of auditory selective attention in aging and Parkinson's disease. Spatial gradients of visual attention: behavioral and electrophysiological evidence. Systematic Reviews: Synthesis of Best Evidence for Clinical Decisions Contextual probability evaluation in autistic, receptive developmental language disorder, and control children: Event-related brain potential evidence
Background The evidence that higher levels of physical activity and /or lower levels of physical inactivity are associated with beneficial health-related outcomes stems mainly from observational studies . Findings from these studies often differ from r and omised controlled trials and systematic review s currently demonstrate mixed results , due partly to heterogeneity in physical activity interventions , method ologies used and population s studied . As a result , translation into clinical practice has been difficult . It is therefore essential that an overview is carried out to compare and contrast systematic review s , and to identify those physical activity interventions that are the most effective in preventing and /or treating major chronic disease . This protocol has been registered on PROSPERO 2013 : CRD42013003523 . Methods We will carry out an overview of Cochrane systematic review s. We will search the Cochrane Data base of Systematic Review s for systematic review s of r and omised controlled trials that have a primary focus on disease-related outcomes . We will restrict review s to those in selected major chronic diseases . Two authors will independently screen search outputs , select studies , extract data and assess the quality of included review s using the assessment of multiple systematic review s tool ; all discrepancies will be resolved by discussing and reaching a consensus , or by arbitration with a third author . The data extraction form will summarise key information from each review , including details of the population ( s ) ( for example , disease condition ) , the context ( for example , prevention , treatment or management ) , the participants , the intervention(s ) , the comparison(s ) and the outcomes . The primary outcomes of interest are the prevention of chronic disease and /or improved outcomes , in the treatment or management of chronic disease . These outcomes will be summarised and presented for individual chronic diseases ( for example , any change in blood pressure in hypertension or glucose control in diabetes ) . Secondary outcomes of interest are to describe the structure and delivery of physical activity interventions  across chronic disease conditions and adverse events associated with physical activity . Discussion We anticipate that our results could inform research ers , guideline groups and policymakers of the most efficacious physical activity interventions in preventing and /or managing major chronic disease Three years ago , we founded this journal focusing on publishing systematic review s , systematic review protocol s , and associated method ological development papers . Systematic review s , which developed in the social sciences in the 1970s , began to gain rapid momentum during the 1990s in response to concerns by policymakers and clinicians about the scientific validity of the prevailing paradigm of traditional narrative review s written by authoritative experts . What distinguished systematic review s was the use of formal explicit methods , in other words pre-specification , of what exactly was the question to be answered , how evidence was search ed for and assessed , and how it was synthesized in order to reach the conclusion . Importantly , these formal methods were described as part of the review itself in a Methods section . In turn , these methods themselves became the subject of hypothesis-testing studies , as investigators sought how best to search for evidence , assess studies for quality or risk of bias , determine under what conditions meta- analysis was justified , and how to best determine and characterize our confidence in the conclusions . The results of these hypothesis-testing studies led over time to improvements in the methods we use for systematic review s. Thus , systematic review s and this journal are part of an ever-evolving process whose foundations are rooted in the scientific method . Today , new forms of review s are appearing . These have emerged in response to policymakers and other stakeholders ’ needs for information , sometimes emergently or urgently , for which the existing systematic review model does not quite fit . Hence , the rapid review , when time is of the essence ; the scoping review , when what is needed is not detailed answers to specific questions but rather an overview of a broad field ; the evidence map , a cousin of scoping review s that commonly has a specific visual presentation of the evidence across a broad field ; and the realist review , where the question of interest includes how and why complex social interventions work in certain situations , rather than assume they either do or do not work at all . As Editors , we regularly get contacted by prospect i ve authors asking whether realist review s , or scoping review s , etc . , are “ within the scope ” for Systematic Review s , and therefore we judge it an opportune time to state our position on this matter . It is our view that all of these new forms of review s are related to systematic review s , similar to the way that different biological Species within the same Family are related to each other . We consider “ systematic review s ” to be the Family and the different forms of review s to be the different species . Just as in the biological classification , where the related organisms must share certain characteristics , so too must the different types of review s share a common characteristic . In this case , what is shared is their foundation in the scientific method , with their methods articulated in advance in sufficient detail that the review can be reproduced by others . A further defining feature is that there are scholars devoted to improving the methods over time via hypothesis-testing studies . Systematic Review s has responded to these emerging techniques and already publishes papers reporting methods and findings from the systematic review family and has for example published an extremely popular series on rapid review s. We would like to consoli date this position and invite su bmi ssion of these new species of review s , as long as they meet the qualifications just listed . We expect this process of evolution to continue and to refine the methods such that in 10 years ’ time , there will appear new , as yet unimagined species of review s— and perhaps some current species of review will become extinct . Thus , it is with the scientific method , which we believe is the foundation that unites the Family of systematic review Background Patients admitted to the intensive care unit with critical illness often experience significant physical impairments , which typically persist for many years following resolution of the original illness . Physical rehabilitation interventions that enhance restoration of physical function have been evaluated across the continuum of recovery following critical illness including within the intensive care unit , following discharge to the ward and beyond hospital discharge . Multiple systematic review s have been published appraising the exp and ing evidence investigating these physical rehabilitation interventions , although there appears to be variability in review methodology and quality . We aim to conduct an overview of existing systematic review s of physical rehabilitation interventions for adult intensive care patients across the continuum of recovery . Methods / design This protocol has been developed according to the Preferred Reporting Items for Systematic Review s and Meta-Analyses Protocol ( PRISMA -P ) guidelines . We will search the Cochrane Systematic Review Data base , Data base of Abstract s of Review s of Effectiveness , Cochrane Central Register of Controlled Trials , MEDLINE , Excerpta Medica Data base and Cumulative Index to Nursing and Allied Health Literature data bases . We will include systematic review s of r and omised controlled trials of adult patients , admitted to the intensive care unit and who have received physical rehabilitation interventions at any time point during their recovery . Data extraction will include systematic review aims and rationale , study types , population s , interventions , comparators , outcomes and quality appraisal method . Primary outcomes of interest will focus on findings reflecting recovery of physical function . Quality of reporting and method ological quality will be appraised using the PRISMA checklist and the Assessment of Multiple Systematic Review s tool . Discussion We anticipate the findings from this novel overview of systematic review s will contribute to the synthesis and interpretation of existing evidence regarding physical rehabilitation interventions and physical recovery in post-critical illness patients across the continuum of recovery . Systematic review registration PROSPERO CRD42015001068 Background The majority of North American adult females do not meet current physical activity recommendations ( 150 min of moderate-to-vigorous intensity physical activity ( MVPA ) per week accrued in ≥10 min bouts ) ultimately placing themselves at increased risk of morbidity and mortality . Working-age females face particular challenges in meeting physical activity recommendations as they have multiple dem and s , including occupational , family and social dem and s. To develop effective interventions to increase MVPA among working-age females , it is necessary to identify and underst and the strongest modifiable determinants influencing these behaviours . Therefore , the objective of this systematic review is to examine the available evidence to identify intrapersonal , social and environmental determinants of MVPA among working-age females . Methods / Design Six electronic data bases will be search ed to identify all prospect i ve cohort studies that report on intrapersonal , social and /or environmental determinants of  MVPA  in working-age females . Grey literature sources including theses , published conference abstract s and websites from relevant organizations will also be included . Articles that report on intrapersonal ( e.g. health status , self-efficacy , socio-economic status ( SES ) , stress , depression ) , social environmental ( e.g. crime , safety , area SES , social support , climate and capital , policies ) , and environmental ( e.g. weather , workplace , home , neighbourhood , recreation environment , active transportation ) determinants of MVPA  in a working-age ( mean age 18–65 years ) female population will be included . Risk of bias will be assessed within and across all included studies using the Tool to Assess Risk of Bias in Cohort Studies and the Grade s of Recommendation , Assessment , Development and Evaluation approach . Harvest plots will be used to synthesize results across all determinants , and meta-analyses will be conducted where possible among studies with sufficient homogeneity . Discussion This review will provide a comprehensive examination of evidence in this field and will serve to highlight gaps for future research on the determinants of MVPA in working-age females and ultimately inform intervention design . Systematic review registration PROSPERO : CRD42014009750 Systematic review s of health systems research commonly limit studies for evidence synthesis to r and omized controlled trials . However , well-conducted quasi-experimental studies can provide strong evidence for causal inference . With this article , we aim to stimulate and inform discussion s on including quasi-experiments in systematic review s of health systems research . We define quasi-experimental studies as those that estimate causal effect sizes using exogenous variation in the exposure of interest that is not directly controlled by the research er . We incorporate this definition into a non-hierarchical three-class taxonomy of study design s - experiments , quasi-experiments , and non-experiments . Based on a review of practice in three disciplines related to health systems research ( epidemiology , economics , and political science ) , we discuss five commonly used study design s that fit our definition of quasi-experiments : natural experiments , instrumental variable analyses , regression discontinuity analyses , interrupted times series studies , and difference studies including controlled before- and -after design s , difference-in-difference design s and fixed effects analyses of panel data . We further review current practice s regarding quasi-experimental studies in three non-health fields that utilize systematic review s ( education , development , and environment studies ) to inform the design of approaches for synthesizing quasi-experimental evidence in health systems research . Ultimately , the aim of any review is practical : to provide useful information for policymakers , practitioners , and research ers . Future work should focus on building a consensus among users and producers of systematic review s regarding the inclusion of quasi-experiments Systematic review s ( SRs ) are an increasingly popular evidence -based tool and are often used to answer complex research questions across many different research domains . Early SR methodology was advanced by social scientists , and the term meta- analysis was coined by a social scientist who also conducted research in psychology . SRs have recently become popular in healthcare and are likely to be beneficial in any field . The aim of this report is to highlight issues in SR conduct with a focus on the field of nutrition and to make recommendations on improving SR conduct in this area . Development of the research question is probably the most important step in conducting an SR . The 4 main components of an answerable question are 1 ) the patient , population , or problem ; 2 ) the intervention , independent variable , or exposure ; 3 ) the comparators ; and 4 ) the dependent variables or outcomes of interest . The question will be used to determine the optimal methods for conducting the SR . SRs often include study design s beyond r and omized trials and do not always include a meta- analysis of the results . Other topics explored include underst and ing and interpreting discordant review s and the importance of reporting tools [ eg , QUality Of Reporting Of Meta-analyses ( QUOROM Statement ) or CONsoli date d St and ards Of Reporting of Trials ( CONSORT Statement ) ] . Recommendations are then provided , such as developing a capacity-building program , search ing the primary literature for research gaps , and extending reporting tools such as the QUOROM Statement to the field of nutrition Replication research is essential for the advancement of any scientific field . In this paper , we argue that prevention science will be better positioned to help improve public health if ( a ) more replications are conducted ; ( b ) those replications are systematic , thoughtful , and conducted with full knowledge of the trials that have preceded them ; and ( c ) state-of-the art techniques are used to summarize the body of evidence on the effects of the interventions . Under real-world dem and s it is often not feasible to wait for multiple replications to accumulate before making decisions about intervention adoption . To help individuals and agencies make better decisions about intervention utility , we outline strategies that can be used to help underst and the likely direction , size , and range of intervention effects as suggested by the current knowledge base . We also suggest structural changes that could increase the amount and quality of replication research , such as the provision of incentives and a more vigorous pursuit of prospect i ve research registers . Finally , we discuss methods for integrating replications into the roll-out of a program and suggest that strong partnerships with local decision makers are a key component of success in replication research . Our hope is that this paper can highlight the importance of replication and stimulate more discussion of the important elements of the replication process . We are confident that , armed with more and better replications and state-of-the-art review methods , prevention science will be in a better position to positively impact public health The Bulletin ’s editorial team has decided to encourage systematic review s. This is an important decision and is to be welcomed . However it is possible that it will not be received positively by all . Some may feel that systematic review s are not suitable for answering wider public health questions , and that the new section will simply result in the publication of systematic review s addressing narrowly focused , clinical questions with a focus on r and omized controlled trials alone.1 There is no reason why this should be so , and there are far too many examples of systematic review s of non- clinical interventions ( including government policies ) , which include non-r and omized studies , to list.2 Systematic review s of qualitative research are also becoming more common.3 Nonetheless misconceptions about the scope and flexibility of systematic review s still surface occasionally and it never fails to surprise me when I stumble across one of these hoary old chestnuts . If it really were true that systematic review s were only for simple , individual-level interventions , systematic review ers working in public health would be very concerned . After all , public health problems require us to draw on complex sets of qualitative as well as quantitative evidence ; and some policy interventions have never been subjected to r and omized controlled trials ( RCTs ) but have been evaluated using other approaches ; everything from controlled and uncontrolled before- and -after studies , to time series analyses , to qualitative methods . In such cases , systematic review s that focused on RCTs alone would have little to say and we would end up producing many “ empty review s ” , which contain no studies at all . These would be undoubtedly quicker to do and quicker to read than the typical systematic review , but would be of limited use for making policy . However this is not the case . In public health we already have a wealth of review s that prioritize RCTs where they are available , but which draw upon a range of other evidence where they are appropriate to answering the review question .2 Take , as an example , transport policies , an important social determinant of health.4 Public health decision-makers have been interested in the effects on health of building new roads for decades , but there has never been a r and omized controlled trial , for obvious reasons . Yet it would make no sense to cl aim that there is no evidence to be review ed ; rather , there have been many controlled and uncontrolled studies that have examined the effects of new roads on respiratory symptoms , injuries , community severance , disturbance and a variety of other outcomes of public health importance . These studies have in fact been systematic ally review ed.5 Many other examples of review s of complex interventions that impact on public health could be given , which appear on the Cochrane Data base and elsewhere,6,7 and such review s are the main focus of the recently-established Cochrane Public Health Review Group . It is also worth noting that both the Cochrane and Campbell Collaboration include increasing numbers of review s that are relevant to low- and middle- income countries,8 though there is a particular need for more systematic review s that consider the effects on equity of the interventions that they include.9 Currently systematic review s have a “ utilitarian bias ” – they tend to be concerned more with the effects on population s and average effects than with distributional effects and impacts in disadvantaged subgroups . It is to be hoped that systematic review s su bmi tted to the Bulletin will routinely consider the effects of interventions on health inequities . The Cochrane Health Equity Field ( http://equity.cochrane.org/en/index.html ) was set up explicitly to further this agenda , to encourage systematic review authors to explicitly assess the effects of interventions not only on the whole population , but on the disadvantaged . So where does this leave non- systematic review s ? Should every review be a systematic review ? This is a difficult question to answer in a short editorial . My own view is that not all review s need to be systematic review s ; there is still a place for review papers that provide a broad overview , and that discuss a range of evidence and make a contribution to wider debates about what might work in particular setting s. However , while such discussion s help place evidence in context and suggest how it may be used , they should not be confused with the evidence -based conclusions of a transparent , scientific review , which systematic ally attempts to find all the relevant evidence , appraises its strengths and limitations in a transparent fashion , and draws that evidence together in such a way that the more robust studies are given greater weight . Finally , the challenges are many . Evidence on interventions to improve public health is in short supply , particularly evidence on social determinants . Systematic review ers therefore face a real challenge in making best use of the sometimes poor , often sparse and usually heterogeneous evidence available to them . It is easy to set narrow inclusion criteria for a review and then sift through the evidence before concluding that there is n’t enough – and what there is , is n’t very good anyway . Such “ evidential nihilism ” is probably not helpful to decision-makers , and public health systematic review ers need to continue to develop new methods and better frameworks within which different types of research evidence can be integrated to inform decision-making . Publishing systematic review s in the Bulletin should give an added impetus to this ongoing work . Objectives . Overview the quality , direction , and characteristics of yoga interventions for treatment of acute and chronic health conditions in adult population s. Methods . We search ed for systematic review s in 10 online data bases , bibliographic references , and h and - search es in  yoga-related  journals . Included review s satisfy Oxman criteria and specify yoga as a primary intervention in one or more r and omized controlled trials for treatment in adults . The AMSTAR tool and GRADE approach evaluated the method ological quality of review s and quality of evidence . Results . We identified 2202 titles , of which 41 full-text articles were assessed for eligibility and 26 systematic review s satisfied inclusion criteria . Thirteen systematic review s include quantitative data and six papers include meta- analysis . The quality of evidence is generally low . Sixteen different types of health conditions are included . Eleven review s show tendency towards positive effects of yoga intervention , 15 review s report unclear results , and no , review s report adverse effects of yoga . Yoga appears most effective for reducing symptoms in anxiety , depression , and pain . Conclusion . Although the quality of systematic review s is high , the quality of supporting evidence is low . Significant heterogeneity and variability in reporting interventions by type of yoga , setting s , and population characteristics limit the generalizability of results We performed an overview of published controlled trials to assess the overall effectiveness of decision aids directed at improving triage of patients with acute chest pain . Search es of the Medline data base identified 11 r and omized or quasi-r and omized controlled trials testing various decision aids : risk stratification system ( n = 6 ) , practice guidelines ( n = 3 ) , and formalized protocol s of care ( n = 2 ) . Sensitivity , specificity of the decision aid and length of stay ( LOS ) in the intensive care unit ( ICU ) were the main outcomes . Decision aids slightly modified sensitivity and specificity ( available in 5 studies ) , but sensitivity was already high in reference groups . Among the 9 studies providing information on LOS , 7 showed a statistically significant difference favoring the decision aid . The level of evidence concerning the efficacy of decision aids in this domain is relatively low . Larger and appropriately design ed clinical trials are required to show an impact on acute cardiac ischaemia complications and mortality In the present study , we compared the performance of normal subjects in three age groups and of medicated Parkinson 's disease patients on auditory selective attention processes . Two tone sequences were dichotically presented . Subjects responded to deviant tones in the attended location .  Event-related potentials ( ERPs ) were recorded from nine scalp electrodes . The old group showed significant decline in hit rate , increase in N1 amplitude , and reduction in P3a , P3b , target negativity , and mismatch negativity amplitude . The amplitude and duration of late Nd increased with age , reflecting modulation of both attended and unattended st and ard ERPs . Although the middle group showed a similar pattern of ERP changes , the effects were generally nonsignificant . The Parkinson 's disease group showed little further disruption of behavioral or ERP measures . However , Parkinson 's disease affected late Nd in the direction opposite of that of aging , reflecting differential modulation of unattended st and ard positivity The spatial distribution of visual attention was investigated by measuring target detectability ( d ' ) and event-related brain potentials ( ERPs ) to stimuli at varying distances from an attended locus . Vertical bars were flashed rapidly in r and om order to 1 of 3 locations : one in each of the lateral visual fields and one on the vertical meridian above the fixation point . Subjects maintained eye fixation while directing their attention to 1 of the 3 locations for the duration of each 1.75 min run . Their primary task was to detect infrequent , shorter target bars at the attended location . A secondary task was to respond to shorter target bars at either of the 2 unattended locations if they ' happened to notice them ' ( without trying to detect them ) . ERPs and d ' scores were obtained to the lateral field stimuli both when they were specifically attended ( primary task ) , as well as when attention was focused upon midline or opposite-field flashes ( secondary task ) . Both d ' scores and the amplitudes of the P135 and N190 waves decreased progressively as attention was directed to locations increasingly distant from a given lateral stimulus . These results support ' gradient ' models of the spatial distribution of visual attention At the end of a long week in the office , you sink back into your chair , reflecting on some of the more memorable patients you cared for and counseled . Through gentle history taking , you discovered that urinary incontinence is the underlying cause of an elderly patient 's increasing social isolation . During a careful physical examination , you detected bruising on the torso of a woman with chronic headaches and began to explore the longst and ing abusive relationship between the woman and her alcoholic partner . You discontinued procainamide therapy in a 72-year-old man who had asymptomatic premature ventricular contractions after myocardial infa rct ion . To prevent bleeding from esophageal varices , you started -blocker therapy in a woman with long-st and ing cryptogenic cirrhosis and portal hypertension . In couples ' therapy , discussing the future quality of life of a middle-aged gay man with human immunodeficiency virus infection , you journeyed through emotionally intense dialogue about advance directives . You presented the risk factors for major and minor bleeding to a 39-year-old woman who was considering warfarin therapy because of recently diagnosed atrial fibrillation and valvular heart disease . You listened to , made diagnoses for , treated , advised , and comforted many patients . Yet there were some hiccoughs in your practice along the way . You stumbled while debating the pros and cons of breast cancer screening with a healthy 48-year-old woman who has been staying current with information on the Internet . You question ed the merits of a personalized walking program suggested to you by a motivated 66-year-old man with severe claudication . Explaining that you wanted to review the best current evidence on these issues , you resolved to address your uncertainties before these patients made their next office visits , in a week 's time . Sighing deeply , you acknowledge that you have little time to read . You subscribe to three journals , which you browse months after they arrive-either when your journal stack becomes precariously high or when your guilt is sufficiently motivational . You sometimes find the conclusions of individual articles conflicting or confusing . You know that some of the decisions and suggestions you made this week , specifically your decisions about stopping procainamide therapy and starting -blocker therapy and your advice about bleeding risks from anticoagulant therapy , were based on the best current research evidence [ 1 - 3 ] . On the other h and , your patients ' inquiries about breast cancer screening and exercise treatment for claudication highlight your need for a concise , current , rigorous synthesis of the best available evidence on each of these topics : in brief , a systematic review [ 4 , 5 ] . Incorporating Research Evidence into Clinical Decision Making The foregoing scenario is familiar to practitioners . In a typical week , we encounter patients with diverse problems ; exercise numerous clinical , interpersonal , and technical skills ; and make many decisions . The factors that affect these decisions and their outcomes are complex . For instance , each patient has unique sociodemographic characteristics , cultural circumstances , and personal preferences . Each physician has unique knowledge , experiences , and values . Moreover , practitioners and their patients make decisions within the context of a rapidly changing health care system that influences the availability , accessibility , and cost of diagnostic tests and therapies [ 6 ] . Timely , useful evidence from the biomedical literature should be an integral component of clinical decision making . If one treatment has been shown to be better than another , we need to know , so that we can recommend the treatment to the appropriate patients . The worldwide effort to develop new tests and treatments , and to determine their usefulness , has never been stronger , and our patients and their families expect us to be fonts of the knowledge that results from this effort [ 7 ] . Unfortunately , it is easy for current best research evidence to pass us by [ 8 ] . We may lack the time , motivation , and basic skills needed to find , critically appraise , and synthesize information , all of which we must do if we are to integrate the results of original studies into our practice . Fortunately , several potent methods are emerging that can greatly enhance our ability to interpret and apply research evidence ; foremost among them is the systematic review . This article begins a series in Annals that will examine systematic review s in detail and explore their many applications . Systematic review s represent the best chance that most practitioners will have to underst and and accurately apply the key signals arising from the robust and increasingly productive search for solutions to medical problems . A properly conducted systematic review faithfully summarizes the evidence from all relevant studies on the topic of interest , and it does so concisely and transparently . What Is a Systematic Review ? Systematic review s are scientific investigations in themselves , with pre-planned methods and an assembly of original studies as their subjects . They synthesize the results of multiple primary investigations by using strategies that limit bias and r and om error [ 9 , 10 ] . These strategies include a comprehensive search of all potentially relevant articles and the use of explicit , reproducible criteria in the selection of articles for review . Primary research design s and study characteristics are appraised , data are synthesized , and results are interpreted . When the results of primary studies are summarized but not statistically combined , the review may be called a qualitative systematic review . A quantitative systematic review , or meta- analysis , is a systematic review that uses statistical methods to combine the results of two or more studies . The term overview is sometimes used to denote a systematic review , whether quantitative or qualitative . Summaries of research that lack explicit descriptions of systematic methods are often called narrative review s. Review articles are one type of integrative publication ; practice guidelines , economic evaluations , and clinical decision analyses are others . These other types of integrative articles often incorporate the results of systematic review s. For example , practice guidelines are systematic ally developed statements intended to assist practitioners and patients with decisions about appropriate health care for specific clinical circumstances [ 11 ] . Evidence -based practice guidelines are based on systematic review s of the literature , appropriately adapted to local circumstances and values . Economic evaluations compare both the costs and the consequences of different courses of action ; the knowledge of consequences that are considered in these evaluations is often generated by systematic review s of primary studies . Decision analyses quantify both the likelihood and the valuation of the expected outcomes associated with competing alternatives . Differences between Systematic and Narrative Review s All review s , narrative and systematic alike , are retrospective , observational research studies and are therefore subject to systematic and r and om error . Accordingly , the quality of a review - and thus its worth-depends on the extent to which scientific review methods have been used to minimize error and bias . This is the key feature that distinguishes traditional narrative review s from systematic review s ( Table 1 ) . If a review is prepared according to the steps outlined in the right column of Table 1 , it is more likely to be systematic and to provide unbiased conclusions . If review methods approximate those found in the middle column of Table 1 , the article is more likely to be a narrative review , and the conclusions are less likely to be based on an unbiased summary of all relevant evidence . Table 1 . Differences between Narrative Review s and Systematic Review s Systematic review s are generated to answer specific , often narrow , clinical questions in depth . These questions can be formulated explicitly according to four variables : a specific population and setting ( such as elderly out patients ) , the condition of interest ( for example , hypertension ) , an exposure to a test or treatment ( such as pharmacologic management ) , and one or more specific outcomes ( such as cardiovascular and cerebrovascular events and mortality ) [ 12 ] . Thus , an example of a well-formulated , clinical ly relevant question is , Does pharmacologic treatment of hypertension in the elderly prevent strokes and myocardial infa rct ions or delay death ? If the question that is driving the review is not clear from the title , abstract , or introduction , or if no methods section is included , the paper is more likely to be a narrative review than a systematic review [ 13 ] . Most narrative review articles deal with a broad range of issues related to a given topic rather than addressing a particular issue in depth [ 9 ] . For example , a narrative review on diabetes ( such as that which might be found in a textbook chapter ) might include sections on the physiology and pathophysiology of carbohydrate , lipid , and protein metabolism ; the epidemiology of and prognosis associated with diabetes ; diagnostic and screening approaches ; and preventive , therapeutic , rehabilitative , and palliative interventions . Thus , narrative review s may be most useful for obtaining a broad perspective on a topic ; they are less often useful in furnishing quantitative answers to specific clinical questions . Narrative review s are appropriate for describing the history or development of a problem and its management . Narrative review s may better describe cutting-edge developments if research is scant or preliminary or if studies are very limited by flawed design or execution [ 13 ] . They may be particularly useful for discussing data in light of underlying theory and context . Narrative review s can draw analogies and can conceptually integrate two independent fields of research , such as Compared 8- to 14-year-old children with either autism or receptive developmental language disorder ( RDLD ) to age- and IQ-matched normal controls in their ability to detect both frequent ( p=.70 ) and infrequent ( p=.30 ) r and omly presented auditory stimuli under task and no-task conditions . Event-related brain potentials ( ERPs ) , behavioral reaction times , and target detection accuracy rates were measured . Although the three groups of children performed in a similar manner on behavioral measures , only the children with autism demonstrated an abnormally small amplitude of the P3b , a component of the ERP . This result is interpreted in terms of ( a ) the consistency of this finding with other ERP studies involving older individuals with autism ; and ( b ) its significance with respect to the difficulty children with autism have in modifying their expectancies to context ually relevant sequences of auditory information
Conclusions drawn from this systematic review suggest that physical activity and cardiorespiratory fitness are associated with P3b modulation during cognitive control and attention tasks .
Acute and chronic physical activity interventions modulate the P3b component , suggesting short- and long-term functional adaptations occurring in the brain to support cognitive processes .
These summary findings suggest physical activity and cardiorespiratory fitness are beneficial to brain function and that P3b may serve as a biomarker of covert attentional processes to better underst and the relationship of physical activity and cognition
Given accumulating evidence indicating that acute and chronic physical activity and cardiorespiratory fitness are related to modulation of the P3b-ERP component , this systematic review provides an overview of the field across the last 30 + years and discusses future directions as the field continues to develop .