Incidence Rates Of Asthma Research Articles

Asthma Incidence in Huelva, Spain at 2 Stages of Life: Childhood and Young Adulthood

Few studies have evaluated the incidence of asthma in Spain. Although more children than adults develop asthma every year, no study to date has analyzed the differences in incidence by following 2 age cohorts in the same geographical area. The aim of this study was to determine changes in wheezing, bronchial hyperreactivity, and asthma (in terms of onset, persistence, and remission), changes in forced expiratory volume in 1 second (FEV(1)), and asthma incidence in children (11-16 years) and young adults (20-44 years) in the city of Huelva, Spain. We analyzed data from 2 groups studied for the first time between 1991 and 1993 and for the second time after an average follow-up period of 9 years. In the first period, data came from the Study of Respiratory Diseases in Huelva (714 children) and the European Community Respiratory Health Survey conducted in the city (271 adults). Both groups answered a respiratory symptom questionnaire, underwent spirometry testing, and completed a nonspecific bronchial challenge test with methacholine. In adults, onset was more common than remission for both wheezing (15.7% vs 6.9%, P=.011) and bronchial hyperreactivity (10.1% vs 3%, P=.017), and asthma incidence was 4.76 cases/1000 person-years. In children, there were more new cases than remissions for wheezing, (24.2% vs 4.3%, P=.001), bronchial hyperreactivity (13.9% vs 5.4%, P=.02), and asthma (9.3% vs 3%, P=.004). The incidence rate for asthma was 15.69 cases/1000 person-years in this age group. The annual decrease in lung function (FEV(1)) was highest in adults with wheezing (34.3 mL) and asthma (54.8 mL). There were more new cases of wheezing and bronchial hyperreactivity than remissions in both children and young adults. Children had a 3.3-fold higher incidence of asthma than adults in Huelva.

Is Childhood Vaccination Associated With Asthma? A Meta-analysis of Observational Studies

The possible link between immunization and atopic diseases has been under intense debate in the last decade. The aim of this study was to systematically review the available evidence on the association of whole-cell pertussis and BCG vaccination with the risk of asthma in childhood and adolescence. The major medical electronic databases (Medline, National Library of Medicine Gateway, and Cochrane Library) were searched, and reference lists of the relevant publications were reviewed for relevant birth-cohort studies and randomized, controlled trials from 1966 to March 2006. Only studies that directly compared vaccinated and unvaccinated children, validated vaccination status by medical charts, and used preset criteria to define asthma were included. Data were abstracted by using a standardized protocol and computerized report form. Results were analyzed by applying a fixed-effect or random-effect model, according to the heterogeneity of the studies. Sensitivity analyses by scoring criteria were performed. Seven studies of pertussis vaccination (with a total of 186,663 patients) and 5 studies of BCG vaccination (with a total of 41,479 patients) met our inclusion criteria. No statistically significant association was detected between either whole-cell pertussis or BCG vaccination and incidence rates of asthma during childhood and adolescence. This lack of a significant association proved to be robust on sensitivity analyses for BCG but not for pertussis vaccine. Currently available data, based on observational studies, do not support an association, provocative or protective, between receipt of the BCG or whole-cell pertussis vaccine and risk of asthma in childhood and adolescence.

Fatores de risco para a asma em adultos, Pelotas, Rio Grande do Sul, Brasil

Asthma incidence and mortality rates have increased in recent years. The present cross-sectional survey aimed to measure asthma prevalence and risk factors in a random sample of 1,968 individuals (20-69 years of age) in Pelotas, Rio Grande do Sul State, Brazil. Overall prevalence of "current asthma symptoms" was 6%, varying according to diagnostic criteria. Associated risk factors in the crude analyses were: female gender, age 60-69 years, non-white skin color, low education, low family income, family history of atopy and asthma, personal history of atopic disease, smoking, low body mass index, and minor psychiatric disorders. In the multivariate analysis the following risk factors remained associated with "current asthma symptoms": mother and father with asthma history, minor psychiatric disorders, age 60-69 years, household income less than 1.01 minimum wage, history of atopic disease, and female gender. The results highlight the variation in asthma prevalence according to diagnostic criteria and confirm the importance of genetic, social, and lifestyle factors.

Socioeconomic Status, Asthma, and Bronchitis in a Large Community Based Study

TM5-O-06 Introduction: Studies have shown increased asthma severity in low social class groups but the relation between socioeconomic status (SES) and asthma in adults is not well understood. We investigated the relationship between SES and the prevalence and incidence of atopic and nonatopic asthma and bronchitis using data from the European Respiratory Health Survey (ECRHS). Methods: We studied prospectively asthma and bronchitis within the ECRHS II. All participants from 12 countries who completed ECRHS I (n = 9023) in 1991 to 1993 were recontacted throughout 1999 to 2001 (ECRHS II, n = 6968). Incidence analysis included subjects who did not report respiratory symptoms or a history of asthma at baseline. SES was based on information relating to the subject's occupation and education level. We calculated prevalence odds ratios (POR) and cumulative incidence ratios (risk ratios, RR) adjusted for age, sex, center, body mass index, family history of asthma, passive smoking, number of siblings, smoking history, rhinitis, respiratory infections before age 5 years, mold or mildew in the home in the last 12 months and occupational exposure to pollutants. Results: The overall prevalence of asthma was 10.4% (11.4% in females vs. 9.4% in males). The cumulative incidence rate of asthma was 5.3% (4.6% for males and 6.0% for females) and for bronchitis, 1.3% (1.2% for males and 1.3% for females) over the 10-year follow-up period. There was a pattern among females of a higher prevalence of asthma with low social class and this was particularly pronounced for non-atopic and low social class (POR = 1.7; 95% CI, 1.0–2.8) and low education level (POR = 1.8; 95% CI, 1.2–2.7). Incidence followed the same pattern, but differences were less pronounced. No systematic differences were observed in men. These differences were only marginally modified when adjusting for potential explanatory variables. Males with a lower education level showed a higher prevalence (POR = 2.6; 95% CI, 1.4–4.9) and incidence of chronic bronchitis (POR = 4.9; 95% CI, 1.2–19.4). Differences in women were less pronounced. Conclusions: Results from this large community-based study do not indicate a systematic pattern by SES for asthma, nor a clear pattern of higher risks for prevalence compared with incidence. A strong negative association was observed for bronchitis. The large sample size and the use of homogeneous criteria concerning outcomes and classification of SES and of confounders in this study makes it unlikely that these findings could be attributed to chance or bias.

CRUDE ASTHMA INCIDENCE RATES AMONG BUFFALO, NY, CHILDREN

PURPOSE: Western New York (Lin et al., 2005; Lin et al., 2002) and the City of Buffalo residents have high asthma prevalence and health care utilization rates for asthma (Lwebuga-Mukasa et al, 2004; Lwebuga-Mukasa & Dunn-Georgiou, 2002). To date there has been no information regarding asthma incidence among this population. The purpose of this study was to determine the crude asthma incidence rate among children.

Incidence of asthma among workers exposed to sulphur dioxide and other irritant gases

The aim of the present study was to investigate whether repeated peak exposure (gassings) to sulphur dioxide (SO2) and other irritant gases increases the risk of new-onset asthma. A questionnaire was sent to 4,112 sulphite workers, of whom 1,919 completed the questionnaire and 396 completed the short-form questionnaire, which was sent out as a last reminder. A sample of 130 nonrespondents completed a telephone interview using the short-form questionnaire. The incidence of adult-onset, physician-diagnosed asthma during employment duration was analysed in relation to exposure to SO2 and gassings giving rise to respiratory symptoms. Incidence rates, as well as incidence rate ratios with 95% confidence interval (CI), were calculated. Further Cox regression models were used allowing assessment of hazard ratios (HR) stratified for sex and adjusted for atopy, smoking habits and age. The incidence rate for asthma among sulphite mill workers reporting gassings of SO2 was 6.2 out of 1,000 person-yrs, compared with 1.9 out of 1,000 person-yrs among subjects unexposed to SO2 and any gassings (HR (95% CI) 4.0 (2.1-7.7)). Among males reporting gassings to SO2, the HR (95% CI) for asthma was 5.8 (2.6-13) compared with unexposed males. In conclusion, repeated peak exposure to sulphur dioxide increased the incidence of asthma during work in sulphite pulp mills, which supports the hypothesis of irritant-induced asthma.

Mode of delivery at birth and development of asthma: A population-based cohort study

To test the hygiene hypothesis, previous studies have assessed the relationship between mode of delivery at birth and asthma incidence, but the results have been inconsistent because of potential selection and ascertainment biases. To assess the relationship between mode of delivery at birth and asthma by following all children born in Rochester, Minn, between 1976 and 1982. From the birth certificate, we determined mode of delivery (cesarean section vs vaginal delivery). Asthma status during the first 7 years of life was ascertained from comprehensive medical record reviews. The association between mode of delivery and asthma status was evaluated in a proportional hazards model adjusted for sex, birth weight, maternal education, and maternal age. The cumulative incidence rates of asthma among children who were born by cesarean section and vaginal delivery were 3.2% versus 2.6%, 4.6% versus 4.6%, 4.6% versus 5.8%, and 5.7% versus 6.7% at the 1st, 3rd, 5th, and 7th years of life, respectively. The adjusted hazard ratios for cesarean section in predicting asthma and wheezing episode were 0.93 (95% CI, 0.6-1.4; P=.71) and 0.93 (95% CI, 0.7-1.3; P=.67), respectively. Mode of delivery is not associated with subsequent risk of developing childhood asthma or wheezing episodes. Because the effect of mode of delivery on a risk of developing asthma or wheezing episodes varies over time (ie, age), selection of the study subjects according to their ages may have influenced the findings of previous studies with a shorter follow-up period.

Gastroesophageal Reflux Disease and Asthma: A Longitudinal Study in UK General Practice

Gastroesophageal reflux disease (GERD) and asthma are common causes for consultation in primary care, but the relationship between the two remains unclear. The aim of our study was to investigate the temporal relationship between first diagnoses of GERD and asthma in general practice. We used the UK General Practice Research Database to identify a cohort of patients with a first diagnosis of GERD (n = 5,653) and another cohort of patients with a first diagnosis of asthma (n = 9,712) during 1996, which we compared with age-matched and sex-matched control cohorts drawn from the general population without either diagnosis. We investigated the incidence of a GERD diagnosis among the asthma patients and control subjects, and the incidence of an asthma diagnosis among the GERD patients and control subjects during a mean follow-up period of 3 years. We calculated the relative risk (RR) of these diagnoses using Cox regression analysis and examined the risk associated with medication use using nested case-control analysis. The incidence rates of GERD and asthma among the control cohorts were 4.4 and 3.8 per 1,000 person-years, respectively. During the follow-up period, the RR of an incident asthma diagnosis in patients with a new diagnosis of GERD was 1.2 (95% confidence interval [CI], 0.9 to 1.6), while the RR of an incident GERD diagnosis among patients with a new diagnosis of asthma was 1.5 (95% CI, 1.2 to 1.8) after adjustment for age, sex, smoking, prior comorbidity, and number of health-care contacts. This increased risk was mainly seen during the first year of follow-up. The prior use of prescription medications for asthma and GERD had no significant effects on the risk of GERD and asthma diagnosis, respectively. Patients with asthma are at a significantly increased risk of developing GERD, mainly during the first year following diagnosis. A nonsignificant increase in the risk of developing asthma was evident among GERD patients. The relationship between GERD and asthma warrants further investigation.

The Incidence of Asthma in Young Adults

Longitudinal data on adult asthma are sparse. The objectives of this study were to determine the incidence of asthma and to establish the risk factors for the development of asthma in subjects who were 12 to 41 years old over an 8-year period. From birth cohorts over the period 1953 to 1982 in The Danish Twin Registry, 19,349 subjects with no history of asthma, as determined by a questionnaire-based survey in 1994, answered a follow-up questionnaire in 2002. The subjects were regarded as incident asthma cases when answering "yes" to the question "Do you have, or have you ever had asthma?" in 2002, and "no" to the same question in 1994. A total of 838 cases (4.3%) of new asthma were identified in 2002. The incidence rates of asthma were 4.5 and 6.4 per 1,000 person-years, respectively, among male and female subjects. For all ages, the probability of adult-onset asthma was greater for female subjects (odds ratio [OR], 1.49; p < 0.001), and for both sexes there was a slow decline in probability with increasing age. There was a positive association between increasing body mass index (BMI) and risk of adult-onset asthma applying to both sexes (OR, 1.05 per unit; p < 0.001). Furthermore, positive associations were found between incident asthma and a history of hay fever (OR: male subjects, 4.2; female subjects, 3.7; p < 0.001), eczema (OR: male subjects, 3.5; female subjects, 2.0; p < 0.001), and both (OR: male subjects, 6.9; female subjects, 8.0; p < 0.001). There is a continuing high incidence of asthma past childhood that is most pronounced among female subjects. Increasing levels of BMI are associated with a greater likelihood of developing asthma for both sexes. A substantial portion of cases of adult asthma is preceded by upper airway allergic symptoms and/or eczema, thus indicating a shared pathogenesis.

Work-Related Asthma in the Spray-On Truck Bed Lining Industry

The objective of this study was to identify work-related asthma (WRA) workers' compensation claims associated with methylene diphenyl diisocyanate (MDI) exposure in the spray-on truck bed lining industry and estimate the asthma incidence rate in this industry. The authors conducted a descriptive study of workers' compensation claims meeting an established surveillance case definition for WRA. Eight WRA workers' compensation claims were identified in the truck bed lining industry in Washington State for a claims incidence rate of 200 per 10,000 full-time equivalent. The medical evaluation of the cases was inadequate because none of the truck bed lining cases had medical testing to objectively link their asthma to the workplace. The rate of work-related asthma in the truck bed lining industry is excessive and suggests a need for significant intervention, including improvements in the clinical assessment provided to MDI-exposed workers.

Hormone replacement therapy and asthma incidence in menopausal women from the third national health and nutrition examination survey (NHANES III, 1988-1994)

RATIONALE: The relation between hormone replacement therapy (HRT) and asthma incidence in menopausal women has been addressed by few studies, with equivocal results. To our knowledge, this important issue has not been addressed in a population representative of menopausal women in the US.METHODS: Data were obtained from NHANES III, a nationally-representative cross-sectional sample of the U.S. population conducted from 1988 to 1994. Incidence rates of asthma were calculated for menopausal women who had never or ever been exposed to HRT. Cox proportional hazards regression was used to model the relationship between HRT exposure and asthma incidence, adjusting for race-ethnicity, smoking, age at menopause, and urban residence.RESULTS: Among 2,894 menopausal women included in the analysis, 997 (33.8%) had been exposed to HRT and 97 (3.35%) developed asthma after menopause. The incidence rates of asthma among unexposed and exposed women in the sample population were 1.54 per 1000 person-years and 2.37 per 1000 person-years, respectively (rate ratio 1.54, 95% CI 1.24, 1.91). In analyses weighted to represent menopausal women in the US population, the adjusted hazard ratio for asthma comparing HRT exposed and unexposed women was 1.88 (95% CI, 1.06, 3.33).CONCLUSIONS: We found that menopausal women who have ever taken HRT are more likely to develop asthma than women who have never taken HRT. The clinical relevance of these findings is highlighted by the possibility that a large percentage of post-menopausal women may be on HRT. RATIONALE: The relation between hormone replacement therapy (HRT) and asthma incidence in menopausal women has been addressed by few studies, with equivocal results. To our knowledge, this important issue has not been addressed in a population representative of menopausal women in the US. METHODS: Data were obtained from NHANES III, a nationally-representative cross-sectional sample of the U.S. population conducted from 1988 to 1994. Incidence rates of asthma were calculated for menopausal women who had never or ever been exposed to HRT. Cox proportional hazards regression was used to model the relationship between HRT exposure and asthma incidence, adjusting for race-ethnicity, smoking, age at menopause, and urban residence. RESULTS: Among 2,894 menopausal women included in the analysis, 997 (33.8%) had been exposed to HRT and 97 (3.35%) developed asthma after menopause. The incidence rates of asthma among unexposed and exposed women in the sample population were 1.54 per 1000 person-years and 2.37 per 1000 person-years, respectively (rate ratio 1.54, 95% CI 1.24, 1.91). In analyses weighted to represent menopausal women in the US population, the adjusted hazard ratio for asthma comparing HRT exposed and unexposed women was 1.88 (95% CI, 1.06, 3.33). CONCLUSIONS: We found that menopausal women who have ever taken HRT are more likely to develop asthma than women who have never taken HRT. The clinical relevance of these findings is highlighted by the possibility that a large percentage of post-menopausal women may be on HRT.

A prospective study of asthma incidence and its predictors: the RHINE study

The objective of this longitudinal study was to estimate the incidence rate of asthma, and to compare the incidence between subjects with or without baseline reporting of certain respiratory symptoms. A follow-up of the random population samples in the European Respiratory Health Survey (ECRHS) in Sweden, Norway, Denmark, Iceland and Estonia was conducted in 1999-2001, in a population aged 30-54 yrs at follow-up (n=14,731). Asthma was defined as reporting either asthma or physician-diagnosed asthma, and a reported year when asthma symptoms were first noticed. Incidence rates, incidence rate ratios and hazard ratios were calculated with 95% confidence intervals. The incidence rate of asthma was 2.2 cases per 1,000 person-yrs. The incidence was higher among females (2.9 cases.1,000 person-yrs(-1)) than among males (1.5 cases.1,000 person-yrs(-1)). When subjects with baseline reporting of wheezing were excluded, the incidence rate decreased to 1.7 cases.1,000 person-yrs(-1), with a further decrease to 1.5 cases.1,000 person-yrs(-1) after exclusion of subjects with wheezing, nocturnal dyspnoea, chest tightness and cough. There was a strong association between onset of asthma and wheezing at baseline. In this prospective, population-based study, the incidence rate of asthma in the whole population sample ranged 1.5-2.2.1,000 person-yrs(-1), with a higher incidence range among females. The incidence was dependent on the extent to which subjects with respiratory symptoms were excluded from follow-up. Hence, for comparability between studies, the exclusion criteria in the follow-up population must be stated.

Incidence and Prevalence of Asthma and Allergic Rhinitis: A Cohort Study of Finnish Adolescents

Only limited data are available about the incidence of asthma and allergic rhinitis based on prospective longitudinal studies throughout childhood into adult life. The main purpose of the study was to estimate the incidence rate of asthma and allergic rhinitis from birth to early adulthood. We also estimated the prevalences of these diseases at 16, 22, and 32 years of age. The data were drawn from a follow‐up survey of a Finnish urban age cohort (1967 birth cohort, N = 2269) from age 16 to age 32 years. All data were based on self‐report. The prevalence of asthma from age 16 to age 32 years changed from 3.0% to 5.0% (males from 3.3% to 4.9%; females from 2.7% to 5.1%); and that of allergic rhinitis from 17.5% to 26.0% (males from 18.7% to 27.8%; females 16.2% to 24.5%), respectively. The overall incidence rate of asthma was approximately 2.1 new cases per 1000 person‐years (95% CI = 1.6–2.8). There was a tendency for boys to have a higher incidence rate of asthma than girls in childhood before 16 years of age: gender difference was reversed from period 17 to 22 years of age. In early adulthood (23–32 years), incidence rates were equal in both sexes. The incidence rate for allergic rhinitis in males was 13.4 per 1000 person‐years (95% CI = 11.8–14.8), slightly greater than in females, 11.4 (95% CI = 10.1–12.8). Among both genders, the highest incidence rate of allergic rhinitis was between 17 and 22 years. Our study adds to the limited knowledge on the incidence rates of asthma and allergic rhinitis.

Adult-onset asthma and wheeze among irritant-exposed bleachery workers.

Whether new-onset asthma is associated with irritant exposure is unclear. The aim was to investigate if occupational exposure to irritant gases, especially repeated peak exposure (gassings), increased the risk of obstructive airways disease. Data on airway symptoms and exposure among bleachery (n = 101) and paper department workers (n = 314) were collected by a questionnaire. Incidence rates and hazard ratios (HR) (Cox regression) were calculated. Non-responders were interviewed by telephone. The incidence rate for adult-onset physician-diagnosed asthma among bleachery workers reporting gassings giving rise to respiratory symptoms was 7.6/10(3) person-years and for those without gassings 2.2/10(3) person-years, compared to 1.0/10(3) person-years for paper workers. In a Cox regression model for asthma (n = 12), stratified for sex, HR for gassings were 5.6 (95% confidence intervals (CI) 1.6-20), for hay fever 3.0 (95% CI 0.8-11), and for ever smoking 0.7 (95% CI 0.2-2.4). The same model for adult-onset wheeze gave HR of 5.2 (95% CI 2.2-12), 1.7 (95% CI 0.6-5.4), and 1.1 (95% CI 0.5-2.7), respectively. Repeated peak exposure to irritant gases, here studied as gassings in the pulp industry, increased the risk for both adult-onset asthma and wheeze.

Risk of Asthma Among Finnish Patients With Occupational Rhinitis

To determine the risk of asthma among patients with occupationally induced rhinitis. Patients with confirmed occupational rhinitis were followed for asthma incidence through register linkage. Patients with other occupational diseases were used as a reference population. Patients entered into the Finnish Register of Occupational Diseases in from 1988 to 1999 for occupational rhinitis (n = 3,637) or other occupational disease (n = 31,457) were observed until December 31, 2000, through two national registers of individuals who were eligible for the reimbursement of asthma medication and the Population Register Center. Incidence rates of asthma were calculated, and a log-linear model, adjusted for age, gender, and occupation, was used to estimate the relative risks (RRs) of asthma among those with occupational rhinitis compared to those with other occupational diseases. There were 420 and 972 incident cases of asthma, respectively, among those with occupational rhinitis and the reference population. The crude RR of asthma was 4.8 (95% confidence interval [CI], 4.3 to 5.4) for all patients with occupational rhinitis, 5.4 (95% CI, 4.8 to 6.2) for those with occupational rhinitis accepted for compensation, and 3.7 (95% CI, 3.1 to 4.5) for patients with unaccepted occupational rhinitis. The RR varied according to occupation and was the highest among farmers and wood workers, both groups having a sevenfold risk. The risk was especially high during the year following notification, but a roughly threefold risk persisted several years thereafter. Patients with occupationally induced rhinitis have a high risk of asthma, but further studies are needed to establish the effect of preventive interventions.

Respiratory Effects of Toluene Diisocyanate in the Workplace: A Discussion of Exposure-Response Relationships

Toluene diisocyanate (TDI) is an important industrial intermediate used in manufacturing flexible polyurethane (PUR) foams, surface coatings, cast elastomers, sealants, and adhesives. In this review long-term trends in workplace exposures to TDI are assessed in both the producing and using industries, and respiratory health effects of TDI are evaluated in relation to workplace TDI concentrations. The key respiratory health effects associated with repeated or long-term TDI exposure are bronchial asthma and an accelerated rate of decline in lung function. In the early years of the industry, annual incidence rates of occupational asthma (OA) due to TDI ranged from 1% to as high as 5 to 6%, depending on the extent of engineering and work practice controls in the various workplaces. Since the mid-1970s, annual OA incidence rates have been <1%, where 8 h TDI concentrations have been maintained below 5 ppb as determined by personal monitoring, even where short-term TDI concentrations above 20 ppb and less frequently above 40 ppb were routinely detected. In these latter settings, there is evidence that the majority of OA cases may be attributable to TDI concentrations well above 20 ppb associated with overexposure incidents. Further study is needed regarding the role of such incidents in inducing respiratory sensitization. Cross-sectional and longitudinal studies of lung function have indicated that continued exposure after development of work-related respiratory symptoms can lead to transient or accelerated fixed declines in forced expiratory volume in 1 sec (FEV1). These findings are congruent with the FEV1 declines demonstrated in general population studies of persons with persistent bronchial hyperresponsiveness or nonoccupational asthma. More recent longitudinal studies in settings with ongoing medical surveillance have provided no consistent evidence of accelerated FEV1 loss among employees exposed up to 5 ppb TDI on an 8 h time-weighted average basis.

Occupational Asthma, Lung Function Decrement, and Toluene Diisocyanate (TDI) Exposure: A Critical Review of Exposure-Response Relationships

An extensive amount of clinical/epidemiological literature exists regarding the effects of toluene diisocyanate (TDI) exposure on respiratory health. This review presents an evaluation and synthesis of that literature with an emphasis on assessing exposure-response relationships in the workplace. The key respiratory disorders examined are bronchial asthma and an accelerated decline in lung function. In the early years of the industry, annual incidence rates of TDI-induced occupational asthma (OA) were as high as 5-6 percent. In settings where mean TDI concentrations have been maintained below 5 ppb based on 8-hr personal samples, OA incidence rates have declined to < 1 percent annually. Recent data also suggest that overexposure incidents may play an important role in inducing OA, particularly in work environments engineered to minimize routine ambient air concentrations. Fourteen studies were reviewed that examined lung function decrement. Early studies from the 1960s and 1970s provided evidence of transient or fixed lung function loss (measured as a decline in forced expiratory volume in one second [FEV1]) during periods of ongoing exposure among employees experiencing high rates of work-related symptoms of OA. Such findings would not be unexpected in that modest FEV1 declines have been demonstrated in general population studies of persons with bronchial hyperresponsiveness or persistent non-occupational asthma. More recent workplace studies have provided no consistent evidence of accelerated FEV1 loss among employees exposed up to 5 ppb TDI (8-hr TWA) even with documented routine short-term TDI concentrations exceeding 20 ppb TDI.

Gender and asthma

The preponderance of epidemiologic evidence demonstrates disparities in asthma burden when comparing females and males. Males develop asthma at a younger age than do females [1], and the incidence of asthma generally is reported to be higher in boys throughout preadolescence, resulting in a 2:1 male predominance in childhood [2,3]. The increased risk for asthma and wheeze among boys reverses at puberty, however, after which the incidence rate of asthma in girls increases, resulting in a 2:1 female predominance among adults [4–6]. These findings are demonstrated by De Marco and colleagues in a retrospective analysis of data from the European Respiratory Health Survey (Fig. 1). In infancy, girls have a lower risk for developing asthma than do boys, with a rate ratio (RR) for girls compared with boys ranging from 0.74 to 0.56 among children 10 years old or younger. At the time of puberty, the risk equalizes in both sexes (RR, 0.84; 95% confidence interval [CI], 0.66–1.12), and after puberty the risk is significantly higher in women than in men, ranging from 1.38 to 5.91 [7]. Among adults aged 25 to 74, being female has been shown to be the strongest predictor of incident cases of asthma [8]. There is evidence for a disparate increase in the prevalence of asthma between men and women. Between 1982 and 1992, the prevalence among US women increased 82% (from 2.9% to 5.4%) compared with an increase of 29% among men (4.0% to 5.1%) [9]. Other investigators suggest that the reversal in the prevalence rates of asthma among young adults is caused by a higher remission rate among boys and a higher incidence rate among girls [10–14].

The risk of asthma among Finnish patients with farmer's lung.

To assess the incidence and risk of asthma in patients with farmer's lung in comparison with farm workers without farmer's lung. The details of farmers and animal-husbandry workers notified in 1988-1999 for farmer's lung ( n=1,272) or other occupational disease ( n=5,045) to the Finnish Register of Occupational Diseases were followed until 31 December 2000 through two national registries of individuals eligible for reimbursement of the cost of asthma medication and the Population Register Center. Incidence rates of asthma were calculated, and a log-linear model adjusted for age, gender and occupation was used to estimate relative risks of asthma among those with farmer's lung compared to those with other occupational disease. Of the patients with farmer's lung, 109 (8.6%) were diagnosed with asthma during the follow-up compared with 202 (4.0%) incident cases of asthma among those in the reference population. The crude relative risk of asthma was 2.1 (95% CI 1.6-2.6) among those with farmer's lung compared with the reference population. The age- and occupation-adjusted relative risk of asthma among patients with farmer's lung was 2.5 (1.8-3.5) in men and 1.4 (1.0-1.9) in women. The rate of asthma was especially high during the first 2 years after notification of farmer's lung. Patients with farmer's lung have an increased risk of developing asthma in comparison to farm workers in general. Most of the cases of asthma occur relatively shortly after the diagnosis of farmer's lung, which should be taken into account in medical follow-up of patients with farmer's lung.

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

Only limited data are available about the incidence of asthma based on longitudinal prospective 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 questionnaire. 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=0·01). 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.