Effect of smoking on hearing loss: quality assessment and meta-analysis

Background. There is an accumulating body of research showing that smoking causes hearing loss; however, the results of these studies have been inconsistent. Methods. Original English articles were retrieved by MEDLINE search using key words “smoking” and “hearing” (1966–2003). Of 166 relevant studies, those that investigated the risk for hearing loss in smokers identified by pure-tone average were selected for review. Studies with an occupational noise-exposed population were excluded. Methodological quality was assessed by a standardized checklist, and then a meta-analysis was performed on studies with discrete numbers of hearing loss among smokers and nonsmokers. Results. A total of 15 (10 cross-sectional, 4 cohort, and one case-control) observational studies were identified; the quality scores of the 9 studies with positive associations between smoking and hearing loss were comparable to those of the remaining 6 studies with insignificant associations. Concerning eight analyzable studies, risk ratios (95% confidence intervals) for hearing loss in smokers were 1.33 (1.24, 1.44) for cross-sectional studies, 1.97 (1.44, 2.70) for cohort studies, and 2.89 (2.26, 3.70) for case-control studies, respectively. Conclusions. The evidence was suggestive of a positive association between smoking and hearing loss. It is possible that smoking cessation may be a useful strategy for maintaining hearing acuity.