Use of Hypnotics and Risk of Cancer: A Meta-Analysis of Observational Studies.

Background: Previous observational epidemiological studies have shown inconsistent results on the relationship between hypnotics use and risk of cancer. To determine the association between hypnotics use and risk of cancer, we conducted a meta-analysis of available literature.

Methods: We searched databases PubMed, EMBASE, and the bibliographies of relevant articles to locate additional publications in February 2016. Three evaluators independently reviewed and selected eligible studies based on pre-determined selection criteria.

Results: A total of six observational epidemiological studies including three case-control studies and three cohort studies, which involved 1,830,434 participants (202,629 hypnotics users and 1,627,805 non-users), were included in the final analyses. In a random-effects meta-analysis, compared with non-use of hypnotics, the odds ratio for overall hypnotics use was 1.29 for various cancers (95% confidence interval, 1.08-1.53). Subgroup meta-analyses by various factors such as study design, type of case-control study, study region, and methodological quality of study revealed consistent findings.

Conclusion: Our findings from a meta-analysis of low-biased epidemiological studies suggested evidence linking the use of hypnotics to an increased risk of cancers. The results should be cautiously interpreted because of considerable heterogeneity with a high I square value.