Smokeless tobacco - a substantial risk for oral potentially malignant disorders in South Asia.

Data sourcesMedline, the Science Citation Index (SCI) via Web of Science, Scopus, CINAHL, Global Index Medicus, Google Scholar and SLT-related reports of the International Agency for Research on Cancer and the National Cancer Institute of the United States.Study selectionObservational studies on the use of SLT and the risk of developing OPMDs in South Asian Populations.Data extraction and synthesisDuplicate selection of studies was undertaken with two reviewers undertaking data abstraction and quality assessment independently. Risk and odds ratios were extracted or calculated for studies where possible. Meta odds ratios (mOR) were calculated using a random effects analysis.ResultsFifteen papers reporting 18 studies were included. The majority (12) were from India. All the studies were case-control designs. MOR for any OPMD with the use of any SLT product was 15.5 (95% CI; 9.9-24.2). Risk was higher in women; mOR = 22.2 (95% CI, 9.1-54.1) than men; mOR = 8.7 (95% CI, 2.1-34.8). Betel quid with tobacco carried the highest risk for OPMD, mOR = 16.1 (95% CI, 7.8-33.5).ConclusionsThe findings of our study point towards a strong association between some forms of OPMDs and SLT use in South Asia. The risk estimates are high, irrespective of controlling for confounders such as smoking and alcohol or stratification by sex, country or source of controls. There is also an exposure-response relationship between OPMDs and SLT use.