Saman Warnakulasuriya1. 1. Guy's, Kings and St Thomas' Dental Institute, Kings College London, London, UK.
Abstract
DATA SOURCES: Source articles were searched for using Medline, the Cochrane Library and within the references lists of identified articles. STUDY SELECTION: Articles were selected that included data enabling construction of 2 x 2 tables to estimate odds ratios (OR) and 95% confidence intervals (CI). DATA EXTRACTION AND SYNTHESIS: For each study, two-way contingency tables were constructed, based on exposure frequency distributions, for cases and controls. Unadjusted OR and 95% CI were recalculated based on the reported data using standard procedures. Separate contingency tables were made for bidi smoking, cigarette smoking and both types of smoking if the data were available in the same article. The overall OR combined across all studies, and its 95% CI, was calculated using a random-effects model for bidi and cigarette smoking. Tests for publication bias and heterogeneity were conducted. Confounding factors, for example, betel quid chewing or alcohol use, were not included in the meta-regression model. RESULTS: An increased risk of oral cancer was found for bidi smokers compared with people who had never smoked (OR, 3.1; 95% 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. CONCLUSIONS: The 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 in the urban poor and rural mass in south Asian countries where bidi smoking is widespread.
DATA SOURCES: Source articles were searched for using Medline, the Cochrane Library and within the references lists of identified articles. STUDY SELECTION: Articles were selected that included data enabling construction of 2 x 2 tables to estimate odds ratios (OR) and 95% confidence intervals (CI). DATA EXTRACTION AND SYNTHESIS: For each study, two-way contingency tables were constructed, based on exposure frequency distributions, for cases and controls. Unadjusted OR and 95% CI were recalculated based on the reported data using standard procedures. Separate contingency tables were made for bidi smoking, cigarette smoking and both types of smoking if the data were available in the same article. The overall OR combined across all studies, and its 95% CI, was calculated using a random-effects model for bidi and cigarette smoking. Tests for publication bias and heterogeneity were conducted. Confounding factors, for example, betel quid chewing or alcohol use, were not included in the meta-regression model. RESULTS: An increased risk of oral cancer was found for bidi smokers compared with people who had never smoked (OR, 3.1; 95% 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. CONCLUSIONS: The 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 in the urban poor and rural mass in south Asian countries where bidi smoking is widespread.