Philippe Leuenberger

Prevalence of Atopy and Pollinosis in the Adult Population of Switzerland (SAPALDIA Study)

The Swiss SAPALDIA study is a large multicenter cross-sectional study initiated in 1991 to evaluate the relationship between environment and respiratory symptoms and diseases in adults, and included subjects from eight areas in Switzerland with distinctive environmental characteristics. We present here prevalence data for atopy, pollinosis and atopic asthma obtained from a random sample of 8,357 adults (18-60 years) assessed by standardized computer-based interview as well as by allergy skin prick tests (SPTs) (performed with Phazet) to grass, birch and Parietaria pollen, house dust mite, cat and dog epithelia and the moulds Alternaria and Cladosporium and by an in vitro allergy screen test (Phadiatop CAP FEIA system). On the basis of a positive Phadiatop (total 28.9%; males 32.9%, females 25.0%; p < 0.001) and/or a positive SPT (total 23%; males 25.0%, females 20.8%; p < 0.001), 32.3% of the study population were considered atopic (males 35.7%, females 28.8%; p < 0.001). Concerning the prevalence of skin sensitization (SPT wheal > or = 3 mm), the highest rate was observed for grass (12.7%), followed by house dust mite (8.9%), silver birch (7.9%), cat (3.8%) and dog (2.8%), whereas moulds and Parietaria elicited less than 1% positive SPTs. The prevalence of atopic rhinitis (rhinitis symptoms associated with atopy) was 13.5% (males 14.3%, females 12.6%; p < 0.05) and the prevalence of current hay fever varied between 9.1% (questionnaire answer and a positive SPT to at least one pollen), 11.2% (questionnaire answer and presence of atopy) to 14.2% (questionnaire answer only) with no significant difference by sex.(ABSTRACT TRUNCATED AT 250 WORDS)

Exposure to motor vehicle traffic and allergic sensitization

We examined the association between the presence of an allergic sensitization and seasonal allergic diseases or symptoms and the exposure to road traffic in Basel, Switzerland. Traffic counts at the domiciles of subjects ranged from 24 to 32,504 cars per 24 hours, with a median of 1,624. To investigate the relation of road traffic and allergies, we matched the data of the traffic inventory of Basel with those of the 820 participants of the SAPALDIA study (Swiss Study on Air Pollution and Lung Diseases in Adults), ages 18-60 years, who had completed a detailed respiratory health questionnaire and had undergone allergy testing (skin prick tests and serologic examinations). We observed a positive association with a sensitization to pollen that was most pronounced among persons with a duration of residence of at least 10 years. The odds ratios (adjusted for educational level, smoking behavior, number of siblings, age, sex, and family history of atopy) for cars, contrasting four exposure categories with the lowest quartile as referent category, were 1.99 [95% confidence interval (CI) = 0.91-4.38], 2.47 (95% CI = 1.06-5.73), and 2.83 (95% CI = 1.26-6.31). These results suggest that living on busy roads is associated with a higher risk for a sensitization to pollen and could possibly be interpreted as an indication for interactions between pollen and air pollutants. We did not, however, find a similar relation between motor vehicle traffic and hay fever or seasonal allergic symptoms, and we saw no trend that increasing traffic exposure was associated with a rise in sensitization rates to indoor allergens.

Associations between lung function and estimated average exposure to NO2 in eight areas of Switzerland

In this paper, we present results from the SAPALDIA study (Swiss Study on Air Pollution and Lung Diseases in Adults) regarding associations between lung function [forced vital capacity (FVC) and forced expiratory volume in 1 second (FEV1)], as assessed during the cross-sectional study in 1991, and average levels of NO2 exposure within the eight study communities. We distinguished average home outdoor exposure and average personal exposure to NO2 and obtained exposure estimates by computing regional averages of passive sampler measurements performed by a random subsample of SAPALDIA participants in 1993. Previous analyses had revealed associations between average lung function and average air pollution levels between communities. The present results show that such associations may also be seen within communities: a 10-μg per m3 increase in average home outdoor and personal exposure to NO2 between zones of residence of the same community was associated with a change in average FVC by −0.59% [95% confidence limits (CL) = 0.01, −1.19] and −0.74% (95% CL = −0.07, −1.41), respectively. These values, however, are smaller than the ones found for the corresponding associations between study communities: −1.67% (95% CL = −1.01, −2.33) and −2.93% (95% CL = −2.11, −3.75), respectively. The different magnitudes of these two types of associations might be explained by differences in spatial variation between various components of air pollution. (Epidemiology 1998;9:405–411)A common strategy for modeling dose-response in epidemiology is to transform ordered exposures and covariates into sets of dichotomous indicator variables (that is, to factor the variables). Factoring tends to increase estimation variance, but it also tends to decrease bias and thus may increase or decrease total accuracy. We conducted a simulation study to examine the impact of factoring on the accuracy of rate estimation. Factored and unfactored Poisson regression models were fit to follow-up study datasets that were randomly generated from 37,500 population model forms that ranged from subadditive to supramultiplicative. In the situations we examined, factoring sometimes substantially improved accuracy relative to fitting the corresponding unfactored model, sometimes substantially decreased accuracy, and sometimes made little difference. The difference in accuracy between factored and unfactored models depended in a complicated fashion on the difference between the true and fitted model forms, the strength of exposure and covariate effects in the population, and the study size. It may be difficult in practice to predict when factoring is increasing or decreasing accuracy. We recommend, therefore, that the strategy of factoring variables be supplemented with other strategies for modeling dose-response.

Accelerated decline in lung function in smoking women with airway obstruction: SAPALDIA 2 cohort study

BackgroundThe aim was to determine if effects from smoking on lung function measured over 11 years differ between men and women.MethodsIn a prospective population based cohort study (Swiss Study on Air Pollution and Lung Diseases in Adults) current smokers in 1991 (18 – 60 yrs) were reassessed in 2002 (n = 1792). Multiple linear regression was used to estimate effects from pack-years of cigarettes smoked to 1991 and mean packs of cigarettes smoked per day between 1991 and 2002 on change in lung volume and flows over the 11 years.ResultsIn both sexes, packs smoked between assessments were related to lung function decline but pack-years smoked before 1991 were not. Mean annual decline in FEV1 was -10.4 mL(95%CI -15.3, -5.5) per pack per day between assessments in men and -13.8 mL(95%CI-19.5,-8.1) in women. Decline per pack per day between 1991 and 2002 was lower in women who smoked in 1991 but quit before 2002 compared to persistent smokers (-6.4 vs -11.6 mL, p = 0.05) but this was not seen in men (-14.3 vs -8.8 mL p = 0.49). Smoking related decline was accelerated in men and women with airway obstruction, particularly in women where decline in FEV1 was three fold higher in participants with FEV1/FVC<0.70 compared to other women (-39.4 vs -12.2 mL/yr per pack per day, p < 0.002).ConclusionThere are differences in effects from smoking on lung function between men and women. Lung function recovers faster in women quitters than in men. Women current smokers with airway obstruction experience a greater smoking related decline in lung function than men.

Air pollution, climate and pollen comparisons in urban, rural and alpine regions in Switzerland (SAPALDIA study)

Abstract The aim of this paper is to show spatial differences and correlations in long- term air pollution measurements in the eight SAPALDIA sites (Swiss Study on Air Pollution and Lung Diseases in Adults, SAPALDIA). In addition, a comparison with climatic parameters and pollen counts are presented in a descriptive way. SAPALDIA investigated health effects from air pollutants and climate in a cross-sectional study (1991) and in a follow-up longitudinal study (1992–1993). Over the period 1991–1993, urban–rural–Alpine concentration gradients were found for SO2, NO2, PM10 and HNO3. For O3, average levels were higher in the Alps but peak levels were higher at sites on the Swiss Plateau. Levels of sulphuric acid were negligibly small; acidity was mainly determined by the content of HNO3. A statistical analysis of long-term data for SO2, NO2, TSP, PM10, HNO3 and size-fractions of suspended particulate matter (SPM) indicated strong correlations.

Étude du biais dû aux non-répondants dans une étude épidemiologique (SAPALDIA)

Within the Swiss Study on Air Pollution and Lung Diseases in Adults (SAPALDIA) 16267 adults aged 18 to 60 years from 8 different locations in Switzerland were randomly selected for answering a questionnaire about respiratory health and have a lung function examination with allergy test. 9561 subjects agreed with the examination (59%) (= responders, R). In order to study the possible influence of the bias introduced by non-responders (NR), 221 subjects who refused to participate among the 966 first subjects selected in Payerne were contacted by phone. 142 accepted a home visit and answered a shortened questionnaire about the main respiratory symptoms and diseases and indicated furthermore the reasons for their refusal. Non-responders have a lower mean educational level and belong to lower social classes than responders. The frequency of respiratory symptoms and diseases, allergies and smoking is similar in R and NR except a higher frequency of wheezing during the last 12 month (R: 12.5%, NR: 5.6%, p = 0.03). The level of carbon monoxide in expired air is higher in NR (17.6 ppm) that in R (11.9 ppm) (p = 0.01). A similar difference exists between NR (30.7 pp) and R (24.8 ppm) among current smokers (p < 0.01). The main reasons for refusal are lack of time (27.5%), lack of interest for medical study (22.6%), fear of health professionals (18.3%) or the existence of a another disease (9.9%). Furthermore, 2.8% of the subjects consider a medical study as useless and refuse principally any participation. The role of local press and media in the decision to participate seems to be important. Globally, the differences between R and NR are minimal and should not influence the validity of the results of the SAPALDIA study.