Incidence of physician-diagnosed asthma in adults--a real incidence or a result of increased awareness? Report from The Obstructive Lung Disease in Northern Sweden Studies. Association between breast feeding and asthma in 6 year old children: findings of a prospective birth cohort study Incidence of probable occupational asthma and changes in airway calibre and responsiveness in apprentice welders Asthma and immunoglobulin E antibodies after respiratory syncytial virus bronchiolitis: a prospective cohort study with matched controls. Incidence and prognosis of asthma and wheezing illness from early childhood to age 33 in a national British cohort Long-term ambient ozone concentration and the incidence of asthma in nonsmoking adults: the AHSMOG Study. Incidence and prevalence of asthma among adult Finnish men and women of the Finnish Twin Cohort from 1975 to 1990, and their relation to hay fever and chronic bronchitis. Asthma and wheezing in the first six years of life. The Group Health Medical Associates. Occupational airborne exposure and the incidence of respiratory symptoms and asthma. Incidence of asthma and its determinants among adults in Spain. Factors influencing the occurrence of airway hyperreactivity in the general population: the importance of atopy and airway calibre. Incidence of asthma and respiratory symptoms by sex, age and smoking in a community study A randomized controlled study on the effectiveness of a multifaceted intervention program in the primary prevention of asthma in high-risk infants. Menopause, postmenopausal estrogen preparations, and the risk of adult-onset asthma. A prospective cohort study. Airways responsiveness, wheeze onset, and recurrent asthma episodes in young adolescents. The East Boston Childhood Respiratory Disease Cohort. The BAMSE project: presentation of a prospective longitudinal birth cohort study. The Indoor Air and Children's Health Study: Methods and Incidence Rates Association between atopic sensitization and asthma and bronchial hyperresponsiveness in swedish adults: pets, and not mites, are the most important allergens. Prospective study of body mass index, weight change, and risk of adult-onset asthma in women. Effects of Air Pollution on the Prevalence and Incidence of Asthma in Children Longitudinal follow-up of the changing gender ratio in asthma from childhood to adulthood: role of delayed manifestation in girls. Breast feeding and allergic diseases in infants—a prospective birth cohort study Incidence and host determinants of probable occupational asthma in apprentices exposed to laboratory animals. Cigarette smoking and incidence of chronic bronchitis and asthma in women.
Only limited data are available about the incidence of asthma  based on longitudinal prospect i ve studies . Further , the results from different studies on incidence vary considerably depending on the age composition of the cohorts under study , the used methods and the criteria for disease . Also among adults high incidence rates have been reported during recent years . The aim of this study was to examine to what extent the incidence of physician-diagnosed asthma could be explained by a real incidence of the disease , and to what extend by an increased diagnostic activity or altered diagnostic praxis . Another aim was to study risk factors for asthma based on incident cases . Three cross-sectional surveys have been performed in the same population sample living in the northern-most province of Sweden , Norrbotten . The first survey was performed in 1986 , and 5698 subjects , 86 % of those invited , responded to a postal question naire . Of these , 4754 subjects ( 83 % ) participated at the third survey in 1996 . After exclusion of all subjects who had reported that they had asthma in 1986 , or had been classified as having asthma in 1986 , 68 men and 98 women ( P=0.02 ) reported in 1996 that they had been diagnosed as having asthma by a physician . Thus , the cumulative incidence for the 10-year period was 3.2 % among men and 4.5 % among women . After correction for subjects who already in 1986 had reported symptoms common in asthma , or had been classified as having chronic bronchitis , 97 subjects with incident asthma remained , which corresponded to an annual incidence rate among men of 1.7 and among women of 2.9/1000 persons year(-1 ) ( P=0.1 ) . Clinical examinations confirmed asthma in a large majority of these 97 subjects . Significant risk factors were family history of asthma , both ex- and current smoking , and female sex . The socio-economic groups manual workers and assistant non-manual employees were associated with incident asthma , although not significantly . The increasing prevalence of asthma among adults during recent 10 - 20 years may to a considerable extent be explained by an increased diagnostic activity or altered diagnostic praxis . Use of different methods when measuring incidence may in part explain the extremely diverging incidence rates of asthma found in different studies Abstract Objectives : To investigate the association between the duration of exclusive breast feeding and the development of  asthma related outcomes in children at age 6 years . Design : Prospect i ve cohort study . Setting : Western Australia . Subjects : 2187 children ascertained through antenatal clinics at the major tertiary obstetric hospital in Perth and followed to age 6 years . Main outcome measures : Unconditional logistic regression to model the association between duration of exclusive breast feeding and outcomes related to asthma or atopy at 6 years of age , allowing for several important confounders : sex , gestational age , smoking in the household , and early childcare . Results : After adjustment for confounders , the introduction of milk other than breast milk before 4 months of age was a significant risk factor for all asthma and atopy related outcomes in children aged 6 years : asthma diagnosed by a doctor ( odds ratio 1.25 , 95 % confidence interval 1.02 to 1.52 ) ; wheeze three or more times since 1 year of age ( 1.41 , 1.14 to 1.76 ) ; wheeze in the past year ( 1.31 , 1.05 to 1.64 ) ; sleep disturbance due to wheeze within the past year ( 1.42 , 1.07 to 1.89 ) ; age when doctor diagnosed asthma ( hazard ratio 1.22 , 1.03 to 1.43 ) ; age at first wheeze ( 1.36 , 1.17 to 1.59 ) ; and positive skin prick test reaction to at least one common aeroallergen ( 1.30 , 1.04 to 1.61 ) . Conclusion : A significant reduction in the risk of childhood asthma at age 6 years occurs if exclusive breast feeding is continued for at least the 4 months after birth . These findings are important for our underst and ing of the cause of childhood asthma and suggest that public health interventions to optimise breast feeding may help to reduce the community burden of childhood asthma and its associated traits . Key messages Asthma is the leading cause of admission to hospital in Australian children and its prevalence is increasing Whether breast feeding protects against asthma or atopy , or both , is controversial Asthma is a complex disease , and the relative risks between breast feeding and asthma or atopy are unlikely to be large ; this suggests the need for investigation in a large prospect i ve birth cohort with timely assessment of atopic outcomes and all relevant exposures Exclusive breast feeding for at least 4 months is associated with a significant reduction in the risk of asthma and atopy at age 6 years and with a significant delay in the age at onset of wheezing and asthma being diagnosed by a doctor Public health interventions to promote an increased duration of exclusive breast feeding may help to reduce the morbidity and prevalence of childhood asthma  and The majority of cross-sectional studies have shown a higher prevalence of ventilatory impairment in welders while only few longitudinal studies were able to detect chronic effects on spirometry or bronchial responsiveness . The aim of the study was to determine the incidence of probable occupational asthma ( OA ) , bronchial obstruction and hyperresponsiveness among 286 students entering an apprenticeship programme in the welding profession . This epidemiological prospect i ve cohort study consisted of a baseline assessment survey and two follow-up assessment s. A respiratory symptom question naire was administered at each visit . Spirometry and methacholine bronchial challenge test results , conducted once prior to onset of exposure and later after an average of 15 months of apprenticeship , were available for 194 subjects . The incidence of probable OA was ∼3 % ( 6 of 194 ) . The incidence of bronchial hyperresponsiveness , defined as a ≥3.2‐fold decrease in the provocative concentration causing a 20 % fall in the forced expiratory volume in one second from baseline to the end of the study was 11.9 % . A statistically significant difference was found between the baseline and end of study for the lung function values . In particular , the forced expiratory volume per cent predicted had significantly dropped by 8.4 % on average . The significance of these early pulmonary function changes in relation to possible chronic effects of exposure to welding fumes and gases remains to be explored OBJECTIVE To study the occurrence of bronchial obstructive symptoms and immunoglobulin ( Ig ) E antibodies after respiratory syncytial virus ( RSV ) bronchiolitis in infancy . Previous studies of this subject have mostly been retrospective or without controls , or the controls have not been followed prospect ively . DESIGN This was a prospect i ve cohort study with matched controls . PARTICIPANTS Forty-seven infants had experienced RSV bronchiolitis severe enough to cause hospitalization at a mean age of 3 1/2 months . For each child with RSV infection , two controls were acquired from the local Child Health Center and matched for date of birth , sex , and residence . Only one control was obtained for one RSV child , and the control group thus contained 93 children . METHODS All the children underwent two follow-up examinations , the first one at a mean age of 1 year and the second at a mean age of 3 years . At the first follow-up , a  skin-prick test against egg white  was performed , and serum  IgG antibodies  against RSV were measured . At the second follow-up , serum IgE antibodies  were measured using screening tests for common food and inhalant antibodies , and  skin-prick tests against egg white , cat , birch , and mite allergen were performed . Hereditary and environmental factors ( passive smoking , indoor furred animals ) and duration of breast-feeding were recorded . RESULTS At the first follow-up , 89 % in the RSV group and 27 % in the control group had IgG antibodies against RSV ( P < .001 ) . At the second follow-up , asthma , defined as three episodes of bronchial obstruction verified by a physician , was found in 11 of 47 children ( 23 % ) in the RSV group and in 1 of 93 children ( 1 % ) in the control group ( P < .001 ) . A positive test for IgE antibodies was noted in 14 of 44 ( 32 % ) RSV children and in 8 of 92 ( 9 % ) children in the control group ( P = .002 ) . An analysis of risk factors for the development of asthma and IgE antibodies on the whole group of 140 children showed that RSV bronchiolitis was the most important risk factor , and a family history of atopy or asthma further increased the risk . CONCLUSIONS Respiratory syncytial virus bronchiolitis during the first year of life apparently is an important risk factor for the development of asthma and sensitization to common allergens during the subsequent 2 years , particularly in children with hereditary for atopy/asthma Abstract Objective : To describe the incidence and prognosis of wheezing illness from birth to age 33 and the relation of incidence to perinatal , medical , social , environmental , and lifestyle factors . Design : Prospect i ve longitudinal study . Setting : Engl and , Scotl and , and Wales . Subjects : 18 559 people born on 3 - 9 March 1958 . 5801 ( 31 % ) contributed information at ages 7 , 11 , 16 , 23 , and 33 years . Attrition bias was evaluated using information on 14 571 ( 79 % ) subjects . Main outcome measure : History of asthma , wheezy bronchitis , or wheezing obtained from interview with subjects ' parents at ages 7 , 11 , and 16 and reported at interview by subjects at ages 23 and 33 . Results : The cumulative incidence of wheezing illness was 18 % by age 7 , 24 % by age 16 , and 43 % by age 33 . Incidence during childhood was strongly and independently associated with pneumonia , hay fever , and eczema . There were weaker independent associations with male sex , third trimester antepartum haemorrhage , whooping cough , recurrent abdominal pain , and migraine . Incidence from age 17 to 33 was associated strongly with active cigarette smoking and a history of hay fever . There were weaker independent associations with female sex , maternal albuminuria during pregnancy , and histories of eczema and migraine . Maternal smoking during pregnancy was weakly and inconsistently related to childhood wheezing but was a stronger and significant independent predictor of incidence after age 16 . Among 880 subjects who developed asthma or wheezy bronchitis  from birth to age 7 , 50 % had attacks in the previous year at age 7 ; 18 % at 11 , 10 % at 16 , 10 % at 23 , and 27 % at 33 . Relapse at 33 after prolonged remission of childhood wheezing was more common among current smokers and atopic subjects . Conclusion : Atopy and active cigarette smoking are major influences on the incidence and recurrence of wheezing during adulthood . Key messages Incidence of wheezing illness at all ages was strongly and consistently related to a history of hay fever or eczema ( atopy ) . Associations with maternal smoking during pregnancy , abdominal pain , and migraine were largely confined to those without atopy Active smoking was a powerful and potentially avoidable risk factor for wheeze starting in adult life among both atopic and non-atopic subjects A quarter of the children with a history of asthma or wheezy bronchitis by age 7 reported wheeze in the past year at age 33 Recurrence of wheezing after prolonged remis- sion during late adolescence was strongly associ- ated with atopy and cigarette smoking We conducted a prospect i ve study of a cohort of 3091 nonsmokers , ages 27 to 87 years , to evaluate the association between long-term ambient ozone exposure and  development of adult-onset asthma .  Over a 15-year period , 3.2 % of males and 4.3 % of females reported new doctor diagnoses of asthma .  For males , we observed a significant relationship between report of doctor diagnosis of asthma and 20-year mean 8-h average ambient ozone concentration  ( relative risk (RR)=2.09 for a 27 ppb increase in ozone concentration , 95 % CI=1.03 to 4.16 ) . We observed no such relationship for females . Other variables significantly related to development of asthma were a history of ever-smoking for males ( RR=2.37 , 95 % CI=1.13 to 4.81 ) , and for females , number of years worked with a smoker ( RR=1.21 for a 7-year increment , 95 % CI=1.04 to 1.39 ) , age ( RR=0.61 for a 16-year increment , 95 % CI=0.44 to 0.84 ) , and a history of childhood pneumonia or bronchitis ( RR=2.96 , 95 % CI=1.68 to 5.03 ) . Addition of other pollutants ( PM10 , SO4 , NO2 , and SO2 ) to the models did not diminish the relationship between ozone and asthma for males . These data suggest that long-term exposure to ambient ozone is associated with development of asthma in adult males STUDY OBJECTIVES To examine the prevalence of asthma and hay fever  , and the incidence and temporal relationships of asthma , hay fever , and chronic bronchitis  among adult twins during a 15-year period . DESIGN Prospect i ve cohort study . PARTICIPANTS A population of 11,540 Finnish adult men and women , initially 18 to 45 years of age , who returned a health question naire in 1975 , 1981 , and 1990 as part of the Finnish Twin Cohort study . METHODS Age-st and ardized prevalences and cumulative incidences among individuals were calculated for asthma , hay fever , and chronic bronchitis . The incidence of asthma among subjects with and without hay fever or chronic bronchitis was analyzed in the entire cohort as well as in twin pairs discordant for incident asthma . RESULTS The prevalence of asthma increased slightly from 1975 ( 2.0 % in men and 2.2 % in women ) to 1990 ( 2.9 % in men and 3.1 % in women ) . The prevalence of hay fever showed a larger increase in men and women ( from 6.8 % and 9.8 % to 11.8 % and 15.3 % , respectively ) . Compared with figures for 1976 to 1981 , no significant increase in asthma incidence occurred from 1982 to 1990 , whereas the incidence of hay fever was lower during the latter period among men ( incidence rate ratio , 0.7 ; 95 % confidence interval , 0.6 to 0.9 ) as was the incidence of chronic bronchitis among women ( incidence rate ratio , 0.7 ; 95 % confidence interval , 0.6 to 0.9 ) . Hay fever and chronic bronchitis were usually diagnosed before asthma . Both diseases increased the risk of asthma significantly on the basis of analyses of all individuals and of discordant twin pairs . CONCLUSIONS The pattern of increase in asthma and hay fever prevalence with time was similar , and hay fever was a strong predictor of asthma . These diseases showed no significant increase in incidence BACKGROUND Many young children wheeze during viral respiratory infections , but the pathogenesis of these episodes and their relation to the development of asthma later in life are not well understood . METHODS In a prospect i ve study , we investigated the factors affecting wheezing before the age of three years and their relation to wheezing at six years of age . Of 1246 newborns in the Tucson , Arizona , area enrolled between May 1980 and October 1984 , follow-up data at both three and six years of age was available for 826 . For these children , assessment s in infancy included measurement of cord-serum IgE levels  ( measured in 750 children ) , pulmonary-function testing before any lower respiratory illness had occurred ( 125 ) , measurement of serum IgE levels at nine months of age ( 672 ) , and question naires completed by the children 's parents when the children were one year old ( 800 ) . Assessment s at six years of age included measurement of serum IgE levels  ( in 460 ) ,  pulmonary-function testing  ( 526 ) , and  skin allergy testing  ( 629 ) . RESULTS At the age of six years , 425 children ( 51.5 percent ) had never wheezed , 164 ( 19.9 percent ) had had at least one lower respiratory illness with wheezing during the first three years of life but had no  wheezing at six years of age , 124 ( 15.0 percent ) had no  wheezing  before the age of three years but had wheezing at the age of six years , and 113 ( 13.7 percent ) had wheezing both before three years of age and at six years of age . The children who had wheezing before three years of age but not at the age of six had diminished airway function ( length-adjusted maximal expiratory flow at functional residual capacity [ Vmax FRC ] ) both before the age of one year and at the age of six years , were more likely than the other children to have mothers who smoked but not mothers with asthma , and did not have elevated serum IgE levels or skin-test reactivity . Children who started wheezing in early life and continued to wheeze at the age of six were more likely than the children who never wheezed to have mothers with a history of asthma ( P < 0.001 ) , to have elevated serum IgE levels ( P < 0.01 ) , to have normal lung function in the first year of life , and to have elevated serum IgE levels ( P < 0.001 ) and diminished values for VmaxFRC ( P < 0.01 ) at six years of age . CONCLUSIONS The majority of infants with wheezing have transient conditions associated with diminished airway function at birth and do not have increased risks of asthma or allergies later in life . In a substantial minority of infants , however , wheezing episodes are probably related to a predisposition to asthma Several prevalence studies have suggested an association between occupational exposure and respiratory symptoms and asthma , but there has been a lack of incidence studies to verify this . This study examined the incidence of respiratory symptoms and asthma in an 11-year Norwegian community cohort study with 2,819 subjects . Predictors examined were sex , age , educational level , lifetime exposure to quartz , asbestos , and dust or fumes , as well as smoking habits and pack-years . The prevalence of exposure to quartz , asbestos , and dust or fumes was , respectively , 3.7 % , 5.0 % , and 28.3 % at baseline . In those exposed to dust or fumes , the odds ratios ( 95 % confidence intervals ) varied between 1.4 ( 1.1 , 1.7 ) and 2.1 ( 1.3 , 3.2 ) for developing respiratory symptoms or asthma after adjusting for sex , age , educational level , and smoking . Between 5.7 % and 19.3 % of the incidence of respiratory symptoms and 14.4 % of the incidence of asthma were attributable to dust or fumes exposure after adjustment for sex , age , educational level , and smoking . In conclusion , airborne occupational exposure increases the incidence of respiratory symptoms and asthma , independent of sex , age , educational level , smoking habits , and pack-years The objective was to measure the incidence of asthma and its determinants in Spain , where the prevalence of asthma is low to medium . A follow-up of subjects participating in the European Community Respiratory Health Survey ( ECRHS ) was conducted in 1998- 1999 ( n = 1,640 , 85 % of those eligible ) . Subjects were r and omly selected from the general population and were 20 to 44 yr old in 1991 - 1993 . Time of follow-up was on average 6.75 yr ( range , 5.3 to 7.9 yr ) . Asthma was defined as reporting ever having had asthma . The incidence of asthma was 5.53 ( 95 % confidence interval , 4.28- 7.16 ) per 1,000 person-years ( 6.88 in females , 4.04 in males ) . Incidence was highest in subjects who at the baseline survey had bronchial hyperresponsiveness ( incidence rate ratio [ IRR ] , 3.85 ) , in those with positive IgE against timothy grass ( IRR , 3.16 ) , and in females ( IRR , 1.80 ) . These results persisted after adjusting for respiratory symptoms at baseline . There was no significant association ( p < 0.2 ) with high total serum IgE , atopy defined by reactivity to any allergen , smoking , occupational exposure , or maternal asthma . A sensitivity analysis using four definitions of population at risk yielded incidence rates varying from 5.53 to 1.50 . In this population of subjects without self-reported asthma or asthma-type symptoms at baseline , bronchial hyperresponsiveness and IgE reactivity to grass appeared as the main determinants of new asthma The factors that determine the occurrence of airway hyperreactivity in the general population are not clearly understood . This study was design ed to assess the independent effects of age , atopy , smoking and airway calibre . In a r and om sample of 2,415 adults aged 18 - 70 yrs we measured reactivity to methacholine as the dose provoking a 20 % fall ( PD20 ) in one-second forced expiratory volume ( FEV1 ) , atopy as the mean skin wheal response to three common environmental allergens , and airway calibre as the baseline FEV1 in absolute terms , as percent predicted ( FEV1 % predicted ) and as percent forced vital capacity ( FEV1 % FVC ) . Hyperreactivity , defined as a PD20 < or = 12.25 mumol , was present in 314 ( 13 % ) of the sample , and before adjustment for FEV1 was more common in females ( independent odds ratio ( OR ) = 2.05 ( 95 % confidence interval 1.6 - 2.7 ) ) , current smokers ( OR = 1.89 ( 1.3 - 2.6 ) ) , atopics ( OR = 1.39 ( 1.3 - 1.5 ) per mm skin wheal ) , and in older age groups ( OR for age 60 - 70 yrs relative to 18 - 29 yrs = 2.70 ( 1.7 - 4.3 ) ) . However , the odds of hyperreactivity were also strongly and independently related to absolute FEV1 ( OR = 0.46 ( 0.27 - 0.77 ) per litre ) , FEV1 % predicted ( OR = 0.96 ( 0.94 - 0.98 ) per percent ) , and FEV1 % FVC ( OR = 0.92 ( 0.90 - 0.94 ) per percent ; combined chi-square on 3 df = 312 , p < < 0.0001 ) . ( ABSTRACT TRUNCATED AT 250 WORDS The purpose of this study was to establish incidence rates for a wide range of respiratory symptoms and asthma , and relate them to sex , age , and smoking habits . A cohort established in 1985 as a r and om sample from the population of Western Norway , aged 15–70 yrs , was followed-up in 1996–1997 . Of the initial cohort of 3,786 subjects , a total of 2,819 replied to mailed question naires  at both baseline and follow-up . The 11‐yrs cumulative incidence of asthma was 4.0 % in males and 3.5 % in females . For respiratory symptoms , the cumulative incidences for both sexes varied between 2.0 % ( dyspnoea grade 4 ) and 25.8 % ( wheezing ) , being higher in females than males for most symptoms . For calculation of odds ratios ( ORs ) multivariate logistic regression analyses were used . The sex and smoking-adjusted incidences increased by age for all symptoms except wheezing and attacks of dyspnoea . Those starting to smoke within the follow-up had ORs of 1.9–2.2 for the cough symotoms compared to never-smokers , after adjusting for sex , age , and pack-yrs . To conclude , the 11‐yrs incidence of dyspnoea increased with increasing pack-yrs , after adjusting for sex , age , and changes in smoking habits . This indicated that when analysing other risk factors , adjustment has to be made for the risks posed by smoking , sex and age BACKGROUND The prevalence of asthma has increased in developed countries in the past 2 decades . The effectiveness of intervention measures on the primary prevention of asthma has not been well studied . OBJECTIVE To assess the effectiveness of a multifaceted intervention program in the primary prevention of asthma in high-risk infants ( in this study , infants are defined as persons from birth to the age of 1 year ) . DESIGN Prospect i ve , prenatally r and omized , controlled study with follow-up through the age of 1 year . SETTING University hospital-based setting s at 2 Canadian centers : Vancouver , British Columbia , and Winnipeg , Manitoba . PARTICIPANTS A total of 545 high-risk infants ( at least 1 first-degree relative with asthma or 2 first-degree relatives with other IgE-mediated allergic diseases ) identified before birth . INTERVENTIONS Avoidance of house dust mite and pet allergens and environmental tobacco smoke , encouragement of breastfeeding , and supplementation with a partially hydrolyzed formula . MAIN OUTCOME MEASURES Probable or possible asthma , rhinitis without apparent colds , and a prick skin test result positive for common inhalant allergens . RESULTS Thirty-eight ( 15.1 % ) of the 251 infants available for assessment in the intervention group and 49 ( 20.2 % ) of the 242 infants available for assessment in the control group fulfilled the criteria for possible or probable asthma ( adjusted relative risk , 0.66 ; 90 % confidence interval , 0.44 - 0.98 ) . Also , 16.7 % of the infants in the intervention group and 27.3 % of the infants in the control group developed rhinitis without colds ( adjusted relative risk , 0.51 ; 90 % confidence interval , 0.35 - 0.74 ) . The incidence of positive skin test results to 1 or more inhalant allergens was similar in both groups ( 4.4 % in the intervention group and 4.6 % in the control group ) . CONCLUSIONS Our multifaceted intervention program result ed in a modest but significant ( P= .04 ) reduction in the risk of possible or probable asthma and rhinitis without apparent colds at the age of 12 months in high-risk infants . In the absence of a vali date d definition of asthma at the age of 12 months , follow-up studies are needed to determine the effectiveness of the intervention program in the primary prevention of asthma in high-risk infants We prospect ively evaluated the association of hormone replacement therapy and  asthma incidence in a cohort of pre- and postmenopausal women 34 to 68 yr of age . During 582 , 135 person-years of follow-up between 1980 and 1990 , 726 new cases of asthma were documented . Postmenopausal women who were never users of replacement hormones  had a significantly lower age-adjusted risk of asthma than premenopausal women ( relative risk = 0.65 ; 95 % confidence interval [ CI ] = 0.46 to 0.92 ) . Among naturally menopausal women , the age-adjusted relative risk of asthma for ever use of postmenopausal hormones was 1.49 ( 95 % CI = 1.10 to 2.00 ) ; for current use of hormones ( conjugated estrogens with or without progesterone ) , 1.50 ( 95 % CI = 0.98 to 2.30 ) ; and for past use , 1.52 ( 95 % CI = 1.08 to 2.13 ) , compared with never use of hormones . Ever users of 10 or more years ' duration had twice the age-adjusted risk of asthma compared with women who never used postmenopausal hormones ( 95 % CI = 1.39 to 2.87 ) . Among current users of conjugated estrogens , there was a positive dose-response demonstrated between daily dose and asthma risk ( p for trend = 0.007 ) . While confirmatory studies are warranted , these data suggest that estrogen plays a role in the pathophysiology of asthma and that long-term use and /or high doses of postmenopausal hormone therapy increase subsequent risk of asthma To describe the role of airways responsiveness in predicting incidence of  wheeze in early adolescence and to examine the association between airways responsiveness and active asthma symptoms , children who had been tested for airways hyperresponsiveness were assessed prospect ively . Of 770 children in the East Boston Childhood Respiratory Disease Cohort who were between 5 and 9 yr of age at time of entry into the study , 281 children received airways challenges during voluntary follow-up conducted between 1980 and 1986 . Each subject presented a sequence of wheeze or asthma diagnosis reports along with a sequence of time-varying covariates , including airways challenge results and symptom and exposure information . A robust " pooled repeated observations " analog of the proportional hazard regression model was used to assess associations among risk factors and the probability of incident wheeze or active asthma . In the analysis of wheeze incidence , airways responsiveness ( elicited via eucapnic hyperventilation with cold air or methacholine challenge ) among those free of a history of wheeze at a given visit was found to be associated with a greater tendency to develop wheezing in the next visit ( odds ratio [ OR ] = 3.91 , 95 % confidence interval [ CI ] = 1.21 , 12.66 ) , after controlling for a constellation of known risk factors . In the analysis of recurrent asthma episodes , airways responsiveness at a given visit was associated with a greater tendency to have an asthma diagnosis reported at the subsequent visit ( OR = 4.2 , 95 % CI = 1.92 , 9.23 ) . For subjects presenting multiple airways responsiveness challenge studies , two successive positive airways responsiveness results were independently associated with a higher likelihood of recurrent asthma episodes . These results confirm the predictive importance of airways responsiveness in the natural history of the development and persistence of asthmatic symptoms The aims of this prospect i ve and longitudinal project are to establish crucial risk factors for asthma and other allergic diseases in childhood , and to study factors of importance for prognosis at already established allergic disease . Socio-economic factors , such as ine quality in health , are also to be addressed . The project started in February 1994 . To reach sufficient power , 4,000 children had to be included . In November 1996 , this number was reached ( 4,093 ) . Inclusion in the study was made at 3 - 4 months of age . At that time , and before induction of allergic disease/ asthma of the child , a question naire focused on exposure , genetics and socio-economic factors was answered . Settled dust was sample d for later analysis of furred animal and mite allergens .  When the children were aged both 1 and 2 years , their parents were asked to fill in new question naires focusing on respiratory and allergic ( skin , gastrointestinal ) symptoms , but also key variables of exposure . Cases with asthma are identified and , for every case , two matched controls drawn . During the following winter , the homes of cases and controls were investigated and the temperature , indoor humidity , air change rate and NO2 measured . Two hundred cases ( 5 % ) were expected to be identified during the first 2 years of the children 's lives . Some 479 homes have now been investigated and 97.7 % of the original 4,093 children still remain in the cohort . The 2-year symptom follow-up ended in November 1998 . The 4-year follow-up started on 1 September 1998 and was planned to be finished in June 2000 . Question naires ( allergic and respiratory symptoms , key variables of exposure at home and day care ) are sent out to all 4,093 families . All children are invited for examination , lung function tests ( PEF , flow-volume , MVV and oxygen clearance ) and physical performance .  Blood is taken from all children ( 20 ml ) . Allergy screening is performed and specific IgE examined . Blood cells will be frozen to allow for later DNA extraction . In subsets ( children with any allergic and /or respiratory manifestation and controls ) , markers of inflammation in blood and urine will be examined , as well as eosinophils in nasal smear . Interviews are carried out to assess the severity of asthma , type/periodicity of health care given , asthma medication and parental sick leave when appropriate . As a separate project , financed by the EU , outdoor pollution as risk factors for asthma and allergies are to be studied within the BAMSE cohort . A follow-up of 8 - 9 years is underway The Indoor Air and Children 's Health Study is a prospect i ve cohort study of the relation between indoor air pollution  and lower respiratory illness ( LRI ) during the first 2 years of life . Information on family and household characteristics was obtained from a health maintenance organization for 1,424 infants enrolled at birth . Data on LRI were abstract ed from medical records . The incidence of all LRI was 48.4 per 100 child-years . Wheezing-associated respiratory illness (WARI)/ asthma was the most common specific LRI , with an incidence of 11.5 per 100 child-years . Total LRI incidence was lowest during the first 6 months of life . Girls had lower incidence than boys [ rate ratio ( RR ) = 0.8 ; 95 % confidence interval ( CI ) = 0.7–0.8 ) ] . With the exception of croup , all LRI were most common during February and March . These results are comparable with those of other prospect i ve studies . Consistent with other studies , self-reported maternal smoking demonstrated an RR of 1.5 ( 95 % CI = 1.2–1.8 ) for total LRI , but the association varied for specific LRIs from 2.3 ( 95 % CI = 1.5–3.0 ) for WARI/asthma to 1.0 ( 95 % CI = 0.7–1.6 ) for bronchitis BACKGROUND Atopic sensitization is a well-known risk factor for asthma and bronchial hyperresponsiveness ( BHR ) . Mites have been regarded as the most important allergens , but the prevalence of sensitization to mites is relatively low in Sweden . OBJECTIVE The aim of the study was to investigate possible associations between sensitization to various allergens and  asthma and BHR in adults . METHODS A r and om sample of 1859 subjects , aged 20 to 46 years , was investigated in a cross-sectional study by using a question naire , skin prick tests ( SPTs ) , specific and total IgE measurements , and methacholine bronchial challenge tests . Possible associations were analyzed univariately and by using multivariate logistic regression analysis and proportional hazard regression analysis . RESULTS Positive SPT and specific IgE results were more common in subjects with asthma and BHR than in subjects without these conditions for all allergens . The independent associations between positive SPT responses and asthma and BHR are given as adjusted prevalence ratios ( PRRs ) : pets and asthma , PRR = 3.6 ; pets and BHR , PRR = 2.0 ; grass and asthma , PRR = 2.0 ; grass and BHR , PRR = 1.7 ; mites and asthma , PRR = 1.4 ; and mites and BHR , PRR = 1.2 . The use of specific IgE measurements instead of SPTs showed essentially similar results . CONCLUSION Cats and dogs were the sensitizing allergens most closely associated with asthma and BHR . The relationships with sensitization to grass and mites were less pronounced BACKGROUND Obesity and asthma are common disorders , and their prevalence rates continue to rise . Although individuals with asthma may gain weight as a result of activity limitations , the relationship between body mass index ( BMI ) , which is calculated as weight in kilograms divided by the square of height in meters , and risk of developing asthma is not known . METHODS We performed a prospect i ve cohort study of female US registered nurses in the Nurses ' Health Study II . In 1991 , after excluding women who died with probable asthma or with incomplete data , there were 85911 participants , aged 26 to 46 years . The main outcome measure was self-report of physician-diagnosed asthma with recent use of an asthma medication . RESULTS From 1991 to 1995 , we identified 1596 incident cases of asthma . In a multivariate model controlling for 9 potential confounding factors ( including age , race , smoking , physical activity , and energy intake ) , the relative risks of asthma for 6 increasing categories of BMI in 1991 were 0.9 , 1.0 ( reference ) , 1.1 , 1.6 , 1.7 , and 2.7 ( P for trend < .001 ) . Stronger associations were found using stricter definitions for asthma , and the finding was present in a variety of subgroups . In analyses controlling for the same variables , as well as BMI at age 18 , women who gained weight after age 18 were at significantly increased risk of developing asthma during the 4-year follow-up period ( P for trend < .001 ) . CONCLUSIONS The BMI has a strong , independent , and positive association with risk of adult-onset asthma . The increasing prevalence of obesity in developed nations may help explain concomitant increases in asthma prevalence Abstract The effects of air pollution on asthmatic symptoms were assessed in a prospect i ve cohort study of 3,049 schoolchildren in 8 different communities in Japan .  Respiratory symptoms in these children were evaluated by question naires every year from the 1st through the 6th grade s. The prevalence of asthma among the 1st grade rs was strongly associated with a history of allergic or respiratory diseases , but it was not associated with concentrations of air pollution . During the follow-up period , incidence rates of asthma were associated significantly with atmospheric concentrations of nitrogen dioxide . Particulate matter less than 10 μm in diameter ( PM10 ) was also associated with a higher incidence of asthma , although the association was not significant . These findings suggest that air pollution , including nitrogen dioxide , may be an important factor in the development of asthma among children in urban districts Boys suffer more often from asthma than girls , while in adults the gender ratio is reversed . It is not clear when exactly this change occurs and by what mechanism . From a cohort of all 5030 German 4th grade pupils ( age 10 years ) in Munich , 274 children with current asthma were identified ( 164 males , 110 females ) through a question naire  , and skin prick tests were performed . These subjects were re-evaluated at ages 14 and 20 years with a question naire . A r and om sample ( n = 1000 ) of all 3538 German children without current asthma at age 10 was also re-evaluated at age 20  ( controls ) . At age 20 , only 24.5 % ( 21 males , eight females ) of the initial asthma group still had symptoms , and their gender ratio remained male dominated . In the controls , 4.8 % ( 48/1000 ) had current asthma at age 20 and these were predominantly female : 6.4 % ( 31/485 ) of control girls vs. 3.3 % ( 17/515 ) of boys ( p = 0.022 ) . Half of the new asthma cases had had no symptoms or diagnoses until age 10 , and atopy at age 10 was not associated with subsequent asthma in these . Asthma at age 10 has no better prognosis in boys than in girls , and the mechanism of the changing gender ratio appears to be late incidence of asthma among girls . Because the latter constitute a considerable part of adult asthma cases , it appears important to further explore this asthma phenotype and the risk factors associated with it Aims : To investigate the effect of breast feeding on  allergic disease in infants up to 2 years of age . Methods : A birth cohort of 4089 infants was followed prospect ively in Stockholm , Sweden . Information about various exposures was obtained by parental question naires when the infants were 2 months old , and about allergic symptoms and feeding at 1 and 2 years of age . Duration of exclusive and partial breast feeding was assessed separately . Symptom related definitions of various allergic diseases were used . Odds ratios ( OR ) and 95 % confidence intervals ( CI ) were estimated in a multiple logistic regression model . Adjustments were made for potential confounders . Results : Children exclusively breast fed during four months or more exhibited less asthma ( 7.7 % v 12 % , ORadj = 0.7 , 95 % CI 0.5 to 0.8 ) , less atopic dermatitis ( 24 % v 27 % , ORadj = 0.8 , 95 % CI 0.7 to 1.0 ) , and less suspected allergic rhinitis ( 6.5 % v 9 % , ORadj = 0.7 , 95 % CI 0.5 to 1.0 ) by 2 years of age . There was a significant risk reduction for asthma related to partial breast feeding during six months or more ( ORadj = 0.7 , 95 % CI 0.5 to 0.9 ) . Three or more of five possible allergic disorders — asthma , suspected allergic rhinitis , atopic dermatitis , food allergy related symptoms , and suspected allergic respiratory symptoms after exposure to pets or pollen — were found in 6.5 % of the children . Exclusive breast feeding prevented children from having multiple allergic disease ( ORadj = 0.7 , 95 % CI 0.5 to 0.9 ) during the first two years of life . Conclusion : Exclusive breast feeding seems to have a preventive effect on the early development of allergic disease — that is , asthma , atopic dermatitis , and suspected allergic rhinitis , up to 2 years of age . This protective effect was also evident for multiple allergic disease Laboratory animal ( LA ) workers are frequently affected with allergic sensitization and occupational asthma ( OA ) . The role of preexposure host factors , in particular airway responsiveness , on the incidence of OA has not been satisfactorily studied . A prospect i ve cohort study of 417 apprentices in animal-health technology  was conducted to investigate the incidence and determinants of probable OA . Question naire and skin-prick tests with common and work-specific allergens were administered on entry and at follow-up visits ( up to three ) from 8 to 44 mo after starting apprenticeship . Responsiveness to inhaled methacholine was assessed at baseline and at follow-up in apprentices who developed a new specific skin sensitization and in control subjects . Preexposure host characteristics and the school attended were compared between cases and all cohort subjects not meeting the criteria for probable OA . Twenty-eight apprentices satisfied the definition for probable OA , i.e. , onset of immediate skin reactivity to > 1 occupational inhalant and > 3.2-fold decrease in the provocative concentration causing a 20 % reduction in FEV(1 ) ( PC(20 ) ) . The incidence of probable OA was 2.7 % ( 28/1,043 person-years ) . Baseline immediate skin reactivity to pets ( rate ratio [ RR ] 4.1 , 95 % confidence interval [ CI ] = 1.6 to 10.8 ) , and bronchial responsiveness ( PC(20 ) < or = 32 versus PC(20 ) > 32 mg/ ml ) ( RR = 2.5 , 95 % CI = 1.0 to 5.8 ) were associated with an increased risk of probable OA ; a lower FEV(1 ) had an apparent , protective effect ( RR = 0.58 , 95 % CI = 0.43 to 0.78 ) . It is concluded that apprentices in animal health show a high incidence of probable OA , and that preexposure airway caliber and responsiveness as well as sensitization to pets are associated with an increased risk STUDY OBJECTIVE To examine the relation of smoking habits and development of asthma in a large cohort of US women . DESIGN Prospect i ve cohort study . PARTICIPANTS Among 74,072 women , 34 to 68 years of age , who were free of major diseases , we documented 671 incident asthma cases and 798 incident cases of chronic bronchitis during 10 years of follow-up . METHODS Age-adjusted relative risk estimates for smoking categories were calculated separately for chronic bronchitis and asthma . RESULTS Risk of chronic bronchitis was significantly higher in current smokers than in never smokers ( relative risk [ RR ] = 2.85 ; 95 % confidence interval [ CI ] = 2.45 to 3.32 ) and increased with the number of cigarettes smoked per day ( p for trend < 0.0001 ) . Approximately 5 years after quitting , chronic bronchitis risk in past smokers approached that in never smokers . In contrast , current smokers were at significantly lower risk for asthma than women who never smoked ( RR = 0.57 ; 95 % CI = 0.46 to 0.71 ) and women who quit ( RR = 0.50 ; 95 % CI = 0.40 to 0.62 ) , possibly because individuals with sensitive airways are less likely to become regular smokers , and smokers who develop respiratory symptoms of any etiology tend to quit . Asthma risk in past smokers initially increased compared with that in never smokers , possibly because of quitting prior to diagnosis in response to symptoms of any etiology , but decreased with time since quitting ( p for trend = 0.007 ) ; within approximately 5 years , the risk did not differ between past and never smokers . CONCLUSION These data suggest that smoking in adults may not be an independent cause of asthma but could exacerbate or be perceived as exacerbating asthma symptoms in susceptible individuals
AIM The aim of this study is to determine what factors have been shown , in prospect i ve studies , to predict the incidence of asthma .
METHODS We performed a systematic review of peer- review ed literature from 1994 to 2004 to determine what factors predict the development of asthma in both children and adults .