Effects of bidi smoking on all-cause mortality and cardiorespiratory outcomes in men from south Asia: an observational community-based substudy of the Prospective Urban Rural Epidemiology Study (PURE)

Background Bidis are minimally regulated, inexpensive, hand-rolled tobacco products smoked in south Asia. We examined the eff ects of bidi smoking on baseline respiratory impairment, and prospectively collected data for all-cause mortality and cardiorespiratory events in men from this region. Methods This substudy of the international, community-based Prospective Urban Rural Epidemiology (PURE) study was done in seven centres in India, Pakistan, and Bangladesh. Men aged 35-70 years completed spirometry testing and standardised questionnaires at baseline and were followed up yearly. We used multilevel regression to compare cross-sectional baseline cardiorespiratory symptoms, spirometry measurements, and follow-up events (all-cause mortality, cardiovascular events, respiratory events) adjusted for socioeconomic status and baseline risk factors between non-smokers, light smokers of bidis or cigarettes (>10 pack-years), heavy smokers of cigarettes only (> 10 packyears), and heavy smokers of bidis (>10 pack-years). Findings 14 919 men from 158 communities were included in this substudy (8438 non-smokers, 3321 light smokers, 959 heavy cigarette smokers, and 2201 heavy bidi smokers). Mean duration of follow-up was 5.6 years (range 1-13). The adjusted prevalence of self-reported chronic wheeze, cough or sputum, dyspnoea, and chest pain at baseline increased across the categories of non-smokers, light smokers, heavy cigarette smokers, and heavy bidi smokers (p< 0.0001 for association). Adjusted cross-sectional age-related changes in forced expiratory volume in 1 s (FEV 1) and FEV 1 /forced vital capacity (FVC) ratio were larger for heavy bidi smokers than for the other smoking categories. Hazard ratios (relative to non-smokers) showed increasing hazards for all-cause mortality (light smokers 1.28 [95% CI 1.02-1.62], heavy cigarette smokers 1.59 [1.13-2.24], heavy bidi smokers 1.56 [1.22-1.98]), cardiovascular events (1.45 [1.13-1.84], 1.47 [1.05-2.06], 1.55 [1.17-2.06], respectively) and respiratory events (1.30 [0.91-1.85], 1.21 [0.70-2.07], 1.73 [1.23-2.45], respectively) across the smoking categories. Interpretation Bidi smoking is associated with severe baseline respiratory impairment, all-cause mortality, and cardiorespiratory outcomes. Stricter controls and regulation of bidis are needed to reduce the tobacco-related disease burden in south Asia.