Effect of indoor air pollution from biomass combustion on prevalence of asthma in the elderly.

In this study I examined the effect of cooking smoke on the reported prevalence of asthma among elderly men and women greater than or equal to 60 years old). The analysis is based on 38,595 elderly persons included in India's second National Family Health Survey conducted in 1998-1999. Effects of exposure to cooking smoke, ascertained by type of fuel used for cooking (biomass fuels, cleaner fuels, or a mix of biomass and cleaner fuels), on the reported prevalence of asthma were estimated using logistic regression. Because the effects of cooking smoke are likely to be confounded with effects of age, tobacco smoking, education, living standard, and other such factors, the analysis was carried out after statistically controlling for such factors. Results indicate that elderly men and women living in households using biomass fuels have a significantly higher prevalence of asthma than do those living in households using cleaner fuels [odds ratio (OR) = 1.59; 95% confidence interval (95% CI), 1.30-1.94], even after controlling for the effects of a number of potentially confounding factors. Active tobacco smoking was also associated with higher asthma prevalence in the elderly, but not environmental tobacco smoke. Availability of a separate kitchen in the house and a higher living standard of the household were associated with lower asthma prevalence. The adjusted effect of cooking smoke on asthma was greater among women (OR = 1.83; 95% CI, 1.32-2.53) than among men (OR = 1.46; 95% CI, 1.14-1.88). The findings have important program and policy implications for countries such as India, where large proportions of the population rely on polluting biomass fuels for cooking and space heating. More epidemiologic research with better measures of smoke exposure and clinical measures of asthma is needed to validate the findings.