Traffic at residential address, respiratory health, and atopy in adults: the National German Health Survey 1998.

Motor vehicle traffic contributes to more than 50% of PM10 in Europe and might have far reaching impacts on human health. We investigated the relationship between residential street type as a surrogate for traffic intensity and the prevalence of respiratory symptoms, atopic diseases, and allergic sensitization in adults. Data from 6896 subjects of the German Health Survey 1998 with complete information on residential street type were used. Multiple logistic regression analyses were applied to model associations between street type categories, and respiratory and atopic outcomes were assessed by screening questionnaire of The European Respiratory Health Survey and specific IgE measurements. Living at extremely or considerably busy roads (23.9% of total study population) compared to roads with no or rare traffic (64.5%) was statistically significantly associated with chronic bronchitis (aOR 1.36 (95% CI) (1.01-1.83)) while nocturnal coughing attacks (past 12 months) (1.24 (0.98-1.57)), wheeze during the past 12 months (1.21 (0.93-57)), and hay fever (1.16 (0.94-1.42)) were marginally increased after adjustment for several potential confounders and for multiple testing. No increased risks were found for asthma (0.97 (0.67-1.42)) and allergic sensitization (1.05 (0.91-1.20)). We conclude that exposure to traffic-related air pollutants increases the risk of nonallergic respiratory symptoms and to a lesser degree the risk of hay fever and allergic sensitization but not the risk of asthma in adults.

Indoor and outdoor air concentrations of BTEX and NO2: correlation of repeated measurements.

Studies on health effects of air pollutants ideally define exposure through the collection of air samples in the participants' homes. Concentrations derived from these samples are then considered as an estimate for the average concentration of air pollutants in the homes. Conclusions drawn from such studies therefore depend very much on the validity of the measured air pollution concentrations. In this paper we analysed repeated BTEX and NO(2) measurements with a time period of several months lying between the two conducted home visits. We investigated the variability of their concentrations over time by determining correlation coefficients and calculating within- and between-home variances. Our population consisted of 631 homes of participants from two cohort studies within the framework of the German study on Indoor Factors and Genetics in Asthma. Air pollutants were measured using passive samplers both indoors and outdoors. The measured BTEX concentrations were poorly correlated, with Pearson's correlation coefficient r ranging from -0.19 to 0.27. Additionally, a considerable seasonal effect could be observed. A higher correlation was found for the NO(2) concentrations with r ranging between 0.24 and 0.55. For the BTEX, the between-home variance was bigger than the within-home variance, for NO(2) both variances were of about the same order. Our results indicate that in a setting of moderate climate like in Germany, the variability of BTEX and NO(2) concentrations over time is high and a single measurement is a poor surrogate for the long-term concentrations of these air pollutants.

Residual analysis in linear regression models with an interval-censored covariate.

Residual analysis is a useful class of techniques for the evaluation of the goodness of a fitted model. Checking the underlying assumptions is important since most linear regression estimators require a correctly specified regression function and independent and identically distributed errors to be consistent. For uncensored data, the examination of the residuals of the fitted model is a standard tool for checking whether or not the underlying model assumptions hold. Such analysis has not been widely developed for censored data. Hillis (Statistics in Medicine 1995; 14:2023-2036) developed a residual plot for model checking when the response variable of a linear model is right-censored, and Gomez et al. (Statistics in Medicine 2003; 22:409-425) proposed residuals in models with interval-censored covariates. In this paper, we propose a new definition of residuals for linear models that incorporate interval-censored covariates. This definition can be also applied when the response variable is interval-censored. These new residuals are shown to perform better in model checking than other types of residuals in this context. We illustrate them with a data set from an AIDS clinical trial study.

Rhinitis and blood pressure in adults.

Recently, a study of 330 adults reported increased systolic blood pressure and higher hypertension rates in men with rhinitis. We replicated this study using data from a population-based sample of 896 subjects participating in the European Respiratory Health Survey and in a study on "Monitoring of Trends and Determinants of Cardiovascular Diseases" in Erfurt, Germany. Rhinitis was assessed by questionnaire, blood pressure was measured using a standardized method, and subjects were asked about current use of any high blood pressure medication. After adjustment for age, body mass index, and smoking, neither average systolic (p = 0.17) nor diastolic blood pressure (p = 0.60) was statistically significantly different between men with and without rhinitis. The adjusted prevalence rate of hypertension was also not different between males with and without rhinitis (p = 0.25). In addition, no statistically significant associations between rhinitis and blood pressure were seen in women. We could not confirm the conclusion of the previous study that men with rhinitis need special attention for blood pressure control.

TLR4 gene variants modify endotoxin effects on asthma.

BACKGROUND: Environmental exposure to endotoxin might have a crucial role in immune maturation and development of asthma. OBJECTIVE: The aim of this study was to investigate whether the effect of endotoxin concentration in settled house dust on asthma is modified by the presence of variation in the TLR4 gene. METHODS: We performed a cross-sectional study within the German follow-up of the European Community Respiratory Health Survey. Multivariate logistic regression analysis and nonparametric effect estimates (S-Plus) were applied to examine the association between endotoxin exposure and diagnosed asthma, related clinical symptoms, and bronchial hyperreactivity (BHR) stratified for noncarriers and carriers of G299/I399 polymorphism in the TLR4 gene. RESULTS: In the noncarrier group (n = 279), the prevalence of asthma was significantly increased with elevated endotoxin levels in house dust with adjusted odds ratio 6.24 (95% CI, 1.33-29.17) in the second tertile, and 4.54 (95% CI, 0.94-21.96) in the third tertile compared with the lowest endotoxin tertile. The carriers of the polymorphisms (n = 55) showed a nonsignificant trend to have a lower risk of asthma (crude odds ratio, 0.67; 95% CI, 0.06-8.06 for the second tertile and 1.33; 95% CI, 0.17-10.58 for the third tertile). We found a similar association for wheeze and endotoxin exposure that was also attenuated in subjects with G299/I399 polymorphisms. CONCLUSIONS: The G299/I399 polymorphisms were associated with a modified response to endotoxin, but the functional relationship still needs clarification.