Bidi smoking and oral cancer: a meta-analysis

Several epidemiological studies suggest that bidi smoking increases the risk of oral cancer. No systematic review, however, has been reported to examine how consistent the evidence is across the studies. We undertook a meta-analysis of epidemiological studies investigating the relationship between bidi smoking and oral cancer. Primary studies were identified through a computerized literature search of Medline. Articles abstracted were all epidemiological studies published as original articles in English during 1966-2002 that included quantitative information on bidi smoking and oral cancer. Summary odds ratios (OR) were calculated based on random effects model. A total of 12 case-control studies used for this meta-analysis provided the summary estimates of OR of bidi smoking for oral cancer compared to that of non-smokers. An increased risk of oral cancer was found for bidi smokers compared to never smokers (OR = 3.1, 95% confidence interval [CI] 2.0-5.0) whereas no significant pattern of risk was found for cigarette smokers (OR = 1.1, 95% CI = 0.7-1.8). There was substantial heterogeneity in the pooled OR estimate. Our results clearly indicate that bidi smokers are at increased risk of oral cancer. It is important that this information be incorporated into smoking prevention and cessation efforts, particularly among the urban poor and rural mass in South Asian countries where bidi smoking is widely prevalent.