Identification of a threshold for biomass exposure index for chronic bronchitis in rural women of Mysore district, Karnataka, India.

BACKGROUND & OBJECTIVES: Exposure to air pollution due to combustion of biomass fuels remains one of the significant risk factors for chronic respiratory diseases such as chronic bronchitis. There is a need to identify the minimum threshold level of biomass index that is significantly associated with chronic bronchitis. This study was undertaken to identify a threshold for biomass exposure index in a rural women population in Mysore district, south India. METHODS: A cross-sectional survey was conducted in a representative population of Mysore and Nanjangud taluks. Eight villages each from Mysore and Nanjangud were randomly selected based on the list of villages from census 2001. A house-to-house survey was carried out by trained field workers using the Burden of Obstructive Diseases questionnaire, which evaluated the biomass smoke exposure and chronic bronchitis. All the women aged above 30 yr were included in the study. RESULTS: A total of 2011 women from Mysore and 1942 women from Nanjangud participated in the study. All women were non-smoking and used biomass fuels as the primary fuel for cooking. A threshold of biomass fuel exposure of 60 was identified on multivariate analysis in Mysore district after adjusting for age, passive smoking and working in a occupational exposure to dust, as the minimum required for a significant association with chronic bronchitis. One in every 20 women in Mysore district exposed to biomass fuel exposure index of 110 or more developed chronic bronchitis. INTERPRETATION & CONCLUSIONS: The minimum threshold of biomass exposure index of 60 is necessary to have a significant risk of developing chronic bronchitis in women. The number needed to harm to develop chronic bronchitis reduces with increasing biomass exposure index and women residing in rural Nanjangud have a higher risk for developing chronic bronchitis as compared to women in Mysore.

Population based studies of cancer survival: scope for the developing countries.

Survival refers to the life of a person after diagnosis of disease, and survival studies have the objective of evaluating the overall performance of a group of patients in terms of quality and quantity of life after the diagnosis or treatment. Potentially there are two approaches for the study of population-based survival; direct (classical) and indirect. The direct approach refers to defining a cohort of patients and collecting follow-up information, whereas the indirect approach uses current data on incidence and mortality for estimating various segments of life. In general, there are numerous difficulties in the conduct of population-based survival studies by the classical method, especially in the set-up of developing countries. These include time and finance required for the conduct of the study, the problem of loss to follow-up and also the time gap between the year of diagnosis of patients and the availability of results on their survival. In fact the problem of time gap is recognized even in the developed world. There have been many studies highlighting these problems and suggesting potential solutions. Generally they have focused on three directions: viz, improving the address information and thereby reducing the loss to follow-up; development of methodologies to deal with the losses to follow-up and indirect studies of cancer survival, thereby obviating the follow-up process. This commentary covers the potential approaches of population-based survival studies, classical survival studies, problems in the same, and methods adopted for their solution. A summary of the conceptual and methodological developments on these concepts, highlighting the scope for the developing countries, is also presented.