Smoking is associated with increased risk of hearing loss, according to a study of more than 50,000 participants over eight years.
Researchers analyzed data from annual health checkups, which included audio testing performed by a technician and a health-related lifestyle questionnaire completed by each participant. They examined the effects of smoking status (current, former, and never smokers), the number of cigarettes smoked per day, and the duration of smoking cessation on the extent of hearing loss. Even after adjusting for factors including occupational noise exposure, researchers noted a 1.2 to 1.6 increased risk of hearing loss among current smokers compared with never smokers.
The study appears in the journal Nicotine & Tobacco Research.
While the association between smoking and high-frequency hearing loss was stronger than that of low-frequency hearing loss, the risk of both high- and low-frequency hearing loss increased with cigarette consumption. The increased risk of hearing loss decreased within five years after quitting smoking.
"With a large sample size, long follow-up period, and objective assessment of hearing loss, our study provides strong evidence that smoking is an independent risk factor of hearing loss," said the study's lead author, Dr. Huanhuan Hu of Japan's National Center for Global Health and Medicine. "These results provide strong evidence to support that smoking is a causal factor for hearing loss and emphasize the need for tobacco control to prevent or delay the development of hearing loss."
Study participants were 20–64 years of age and free of hearing loss at baseline. Pure-tone audiometric testing was performed annually to identify hearing loss at 1 and 4 kHz. During follow-up, 3,532 individuals developed high-frequency hearing loss, and 1,575 developed low-frequency hearing loss. The hazard ratio (HR) associated with current smokers was 1.6 (95% confidence interval [CI], 1.5–1.7) and 1.2 (95% CI, 1.1–1.4) for high- and low-frequency hearing loss, respectively, as compared with never smokers. The risk of high- and low-frequency hearing loss increased with the number of cigarettes smoked per day. The HR associated with former smokers was 1.2 (95% CI, 1.1–1.3) and 0.9 (95% CI, 0.8–1.1) for high- and low-frequency hearing loss, respectively.
Nicotine and Tobacco Research is sponsored by the Society for Research on Nicotine and Tobacco. It is published on behalf of the society by Oxford Journals.