[Prevalence of asthma among adults in France, data from the Constances cohort study]. / Prévalence de l'asthme chez l'adulte en France, données de la cohorte Constances.

INTRODUCTION: The objectives of our study were to estimate the prevalence of asthma in adults in France and to study the effects of gender on the associations of asthma with the corpulence and socio-economic characteristics of individuals. METHODS: We estimated the prevalence of current asthma (asthma attack in the past 12 months or current treatment for asthma) from data collected at inclusion in the Constances cohort study in 2013-2014. Analyses were performed separately in men and women, using robust Poisson regression for multivariate analysis. RESULTS: Using data from 34,100 participants in the cohort (men: 47.7 %; mean age: 44.6 years), the prevalence of current asthma was estimated to be 5.8 % (5.1 % in men, 6.4 % in women). The risk of asthma was increased in women with high body mass index (BMI) or waist circumference. In men, only a high waist circumference was associated with an increased risk of asthma. An association with low socioeconomic status was observed only among women. CONCLUSION: The associations of asthma with corpulence and socioeconomic status differed between men and women. Additional analyses should provide a better understanding of the mechanisms responsible for these differences.

Development of a job-task-exposure matrix to assess occupational exposure to disinfectants among US nurses.

OBJECTIVES: Occupational exposure to disinfectants is associated with work-related asthma, especially in healthcare workers. However, little is known about the specific products involved. To evaluate disinfectant exposures, we designed job-exposure (JEM) and job-task-exposure (JTEM) matrices, which are thought to be less prone to differential misclassification bias than self-reported exposure. We then compared the three assessment methods: self-reported exposure, JEM and JTEM. METHODS: Disinfectant use was assessed by an occupational questionnaire in 9073 US female registered nurses without asthma, aged 49-68 years, drawn from the Nurses' Health Study II. A JEM was created based on self-reported frequency of use (1-3, 4-7 days/week) of 7 disinfectants and sprays in 8 nursing jobs. We then created a JTEM combining jobs and disinfection tasks to further reduce misclassification. Exposure was evaluated in 3 classes (low, medium, high) using product-specific cut-offs (eg, <30%, 30-49.9%, ≥50%, respectively, for alcohol); the cut-offs were defined from the distribution of self-reported exposure per job/task. RESULTS: The most frequently reported disinfectants were alcohol (weekly use: 39%), bleach (22%) and sprays (20%). More nurses were classified as highly exposed by JTEM (alcohol 41%, sprays 41%, bleach 34%) than by JEM (21%, 30%, 26%, respectively). Agreement between JEM and JTEM was fair-to-moderate (κ 0.3-0.5) for most disinfectants. JEM and JTEM exposure estimates were heterogeneous in most nursing jobs, except in emergency room and education/administration. CONCLUSIONS: The JTEM may provide more accurate estimates than the JEM, especially for nursing jobs with heterogeneous tasks. Use of the JTEM is likely to reduce exposure misclassification.

Longitudinal study of maternal body mass index, gestational weight gain, and offspring asthma.

BACKGROUND: Sparse data are available on the relationship between prenatal exposures and asthma during later childhood. In a longitudinal study of adolescents and their mothers, we examined the association of (i) maternal prepregnancy body mass index (BMI) and (ii) gestational weight gain (GWG), with incidence of allergic and nonallergic asthma in offspring. METHODS: Analyses were conducted using data from 12 963 children aged 9-14 years at enrolment in the Growing Up Today Study, and their mothers, who are participants in the Nurses' Health Study II. Physician-diagnosed asthma and allergies were assessed by questionnaires sent regularly to participants and their mothers. Logistic regression was used to evaluate associations of maternal BMI and GWG with offspring asthma, overall and by subtype. RESULTS: Physician-diagnosed asthma during childhood or adolescence was reported by 2694 children (21%). Maternal prepregnancy overweight (OR: 1.19, 95% CI: 1.03-1.38) and obesity (1.34, 1.08-1.68) were associated with offspring asthma. In asthma subtype analyses, the association was seen only for asthma onset before age 12 years. Moreover, the association of maternal obesity with nonallergic asthma was observed in boys (2.39, 1.40-4.09) and not in girls (0.96, 0.50-1.85; Pinteraction = 0.03); the opposite pattern was suggested for allergic asthma. With regard to GWG, an association was suggested between gains of <15 lb and higher risk of offspring asthma (1.28, 0.98-1.66), without clear allergy- or sex-related patterns. CONCLUSION: The relation of several prenatal factors to risk of childhood asthma supports the early origins hypothesis for asthma. The observed allergy- and sex-specific patterns suggest multiple etiologic pathways.

[Genetic and environmental factors of asthma and allergy: Results of the EGEA study]. / Facteurs génétiques et environnementaux de l'asthme et de l'allergie: synthèse des résultats de l'étude EGEA.

INTRODUCTION AND METHODS: The EGEA study (epidemiological study on the genetics and environment of asthma, bronchial hyperresponsiveness and atopy), which combines a case-control and a family-based study of asthma case (n=2120 subjects) with three surveys over 20 years, aims to identify environmental and genetic factors associated with asthma and asthma-related phenotypes. We summarize the results of the phenotypic characterization and the investigation of environmental and genetic factors of asthma and asthma-related phenotypes obtained since 2007 in the EGEA study (42 articles). RESULTS: Both epidemiological and genetic results confirm the heterogeneity of asthma. These results strengthen the role of the age of disease onset, the allergic status and the level of disease activity in the identification of the different phenotypes of asthma. The deleterious role of active smoking, exposure to air pollution, occupational asthmogenic agents and cleaning products on the prevalence and/or activity of asthma has been confirmed. Accounting for gene-environment interactions allowed the identification of new genetic factors underlying asthma and asthma-related traits and better understanding of their mode of action. CONCLUSION: The EGEA study is contributing to the advances in respiratory research at the international level. The new phenotypic, environmental and biological data available in EGEA study will help characterizing the long-term evolution of asthma and the factors associated to this evolution.

[Causal analysis approaches in epidemiology]. / Approches d'analyse causale en épidémiologie.

Epidemiological research is mostly based on observational studies. Whether such studies can provide evidence of causation remains discussed. Several causal analysis methods have been developed in epidemiology. This paper aims at presenting an overview of these methods: graphical models, path analysis and its extensions, and models based on the counterfactual approach, with a special emphasis on marginal structural models. Graphical approaches have been developed to allow synthetic representations of supposed causal relationships in a given problem. They serve as qualitative support in the study of causal relationships. The sufficient-component cause model has been developed to deal with the issue of multicausality raised by the emergence of chronic multifactorial diseases. Directed acyclic graphs are mostly used as a visual tool to identify possible confounding sources in a study. Structural equations models, the main extension of path analysis, combine a system of equations and a path diagram, representing a set of possible causal relationships. They allow quantifying direct and indirect effects in a general model in which several relationships can be tested simultaneously. Dynamic path analysis further takes into account the role of time. The counterfactual approach defines causality by comparing the observed event and the counterfactual event (the event that would have been observed if, contrary to the fact, the subject had received a different exposure than the one he actually received). This theoretical approach has shown limits of traditional methods to address some causality questions. In particular, in longitudinal studies, when there is time-varying confounding, classical methods (regressions) may be biased. Marginal structural models have been developed to address this issue. In conclusion, "causal models", though they were developed partly independently, are based on equivalent logical foundations. A crucial step in the application of these models is the formulation of causal hypotheses, which will be a basis for all methodological choices. Beyond this step, statistical analysis tools recently developed offer new possibilities to delineate complex relationships, in particular in life course epidemiology.

Farming in childhood, diet in adulthood and asthma history.

The decrease in the number of children living on traditional farms in France during early childhood and changes in diet could both play a role in the increase in asthma prevalence over the last decades. This study aimed to assess 1) the association of farming lifestyle in childhood and asthma, and 2) whether diet in adulthood modifies the association between farming lifestyle in childhood and adult-onset asthma. In the French Etude Epidemiologique des Femmes de la Mutuelle Générale de l'Education Nationale (E3N) study (54,018 females; age 43-68 yrs), three indicators of farming lifestyle were defined: one using individual data (having farmer parents) and two using ecological data (born in a rural area and exposure to cattle). All farming lifestyle indicators were related to childhood- (<16 yrs) and adult-onset asthma (OR (95% CI) values for farmer parents were 0.54 (0.42-0.70) and 0.72 (0.62-0.84), respectively), and to diet in adulthood, in particular to high fruit and low wine intakes. The association between farmer parents and adult-onset asthma was not modified by diet in adulthood. Results extend previous observations in younger cohorts on the protective role of contact with livestock and farming lifestyle on asthma, in particular during childhood.

Dietary patterns and asthma in the E3N study.

The aim of the present study was to determine dietary patterns and investigate their association with asthma incidence, current asthma and frequent asthma exacerbations. Dietary habits and asthma data were collected from the large E3N study (of French females, mostly teachers). Of the 54,672 females followed-up in 2003, 2,634 reported ever-adulthood asthma, 1,063 reported current asthma, 206 reported frequent asthma attacks (one or more a week), and 628 reported asthma onset between 1993 and 2003. Using principal component analysis, three dietary patterns were identified: the "prudent" pattern (fruits and vegetables); the "Western" pattern (pizza/salty pies, dessert and cured meats); and the "nuts and wine" pattern. Pattern scores were categorised into tertiles, and the incidence and prevalence of asthma was compared between tertiles. After adjustment for confounders, no association of dietary patterns was observed with asthma incidence, ever-asthma or current asthma. The Western pattern was associated with an increased risk of reporting frequent asthma attacks (highest versus lowest tertile odds ratio (OR) 1.79, 95% confidence interval (CI) 1.11-3.73). Increasing scores of the nuts and wine pattern were associated with a decreased risk of reporting frequent asthma attacks (highest versus lowest tertile OR 0.65, 95% CI 0.31-0.96). The results of the present study suggest that overall diet could be involved in frequent asthma exacerbations, one aspect of asthma severity.

[Environmental factors for asthma severity and allergy: results from the EGEA study]. / Facteurs environnementaux de l'asthme sévère et de l'allergie: résultats de l'étude EGEA.

INTRODUCTION: EGEA (Epidemiological study on the genetics and environment of asthma, bronchial hyperresponsiveness and atopy), a case control and family study including 2048 individuals, was initiated to look for environmental and genetic risk factors for asthma. A synthesis of the results obtained since 2002 on phenotypic and environmental aspects of asthma severity and allergy are presented in this article. METHODS AND RESULTS: The results support a role for hormonal factors in asthma severity and in various allergic markers of asthma. A greater body mass index was related to a more severe asthma in women with early menarche. Associations between markers of allergy (eosinophils, IgE and atopy) and hormonal dependent events in women (premenstrual asthma, menopause and oral contraceptive use) have been found. In asthmatics, exposure to agents known to be associated with occupational asthma, active and passive smoking were associated with an increased clinical asthma severity score. The study underlines the protective role of country living and exposure to pets in early life on allergy markers in adulthood, supporting the hygiene hypothesis. CONCLUSIONS: New hypothesis will be tested in the near future from the second stage of this survey.

Fruit and vegetable intakes and asthma in the E3N study.

BACKGROUND: A study was undertaken to investigate whether dietary intake predicted the prevalence of adult asthma among French women participating in the E3N study. METHODS: Of 68 535 women who completed a food frequency questionnaire in 1993 which included 238 food items, 2145 (3.1%) reported having asthma. The distribution of food intake was divided into quartiles (Q(1)-Q(4)) and the prevalence of asthma was compared between the different quartiles (lowest as reference) using logistic regression models on cross sectional data. RESULTS: After adjusting for age, body mass index, menopausal status, smoking status, total caloric intake, physical activity, and use of dietary supplements, women who had a greater intake of tomatoes (OR(Q1-Q4) 0.85 95% CI 0.75 to 0.96, test for trend p = 0.02), carrots (OR(Q1-Q4) 0.81 95% CI 0.72 to 0.92, test for trend p = 0.0003), and leafy vegetables (OR(Q1-Q4) 0.82 95% CI 0.73 to 0.93, test for trend p = 0.0009) had a lower prevalence of asthma. Apples were marginally related to the prevalence of asthma. No other fruits or vegetables were significantly associated with asthma prevalence. CONCLUSIONS: These results suggest that the intake of some vegetables may decrease the prevalence of adult asthma.