Prevalence and Predictors of Asthma in the Megacity of Pakistan: Findings from the Adult Asthma Study-Karachi

Abstract

Background/Aim: Scarce data is available regarding burden of asthma from spirometry-based epidemiological surveys, especially from low and middle income countries. This study was conducted to determine the prevalence and predictors of asthma among adults in Karachi, Pakistan. Methods: A multi-stage, community based cross-sectional survey was conducted from May 2014-August 2015 comprising of 1630 adults (≥ 18 years) from 75 randomly selected (out of 9400) clusters in Karachi. From each cluster, 25 households were randomly selected and all eligible participants were recruited. Data were collected through questionnaire-based interviews in Urdu, consisting of respiratory health related questions (American Thoracic Society (ATS) questionnaire), socio-demographic characteristics and risk factors for asthma. Pre and post-bronchodilator spirometry was performed according to the ATS criteria. The prevalence of asthma was calculated considering presence of respiratory symptoms with reversibility on spirometry (≥ 12% increase, post-bronchodilator) and/or history of physician-diagnosed asthma. Results: The overall prevalence of asthma was 6.6% (n=61; 95% CI: 5.0-8.1) among 930 participants with acceptable spirometry data. Asthma was less likely among the younger age group (AOR: 0.2, 95% CI: 0.1-0.6) and those having birds and animals at home (AOR: 0.5, 95% CI: 0.2-0.9). Asthma was more likely to occur among participants with history of allergies (AOR: 2.8, 95% CI: 1.6-4.9) and those exposed to passive smoking at home (AOR: 1.9, 95% CI: 1.1-3.4). Conclusions: This is the first robust epidemiological assessment regarding actual burden of asthma among adults in Pakistan, reporting a high burden in the country.