Huanhuan Hu, Naoko Sasaki, Takayuki Ogasawara, Satsue Nagahama, Shamima Akter, Keisuke Kuwahara, Takeshi Kochi, Masafumi Eguchi, Ikuko Kashino, Taizo Murakami, Makiko Shimizu, Akihiko Uehara, Makoto Yamamoto, Tohru Nakagawa, Toru Honda, Shuichiro Yamamoto, Ai Hori, Chihiro Nishiura, Hiroko Okazaki, Teppei Imai, Akiko Nishihara, Toshiaki Miyamoto, Kentaro Tomita, Isamu Kabe, Tetsuya Mizoue, Naoki Kunugita, Seitaro Dohi

We aimed to determine the prospective association of smoking status, smoking intensity, and smoking cessation with the risk of hearing loss in a large Japanese cohort. The cohort study included 50195 employees, who were aged 20-64 years and free of hearing loss at baseline. Participants were followed up for a maximum of 8 years. Pure-tone audiometric testing was performed annually to identify hearing loss at 1 and 4 kHz. Cox proportional hazards regression models were used to investigate the association between smoking and hearing loss. During follow-up, 3532 individuals developed high-frequency hearing loss, and 1575 developed low-frequency hearing loss. The hazard ratio (HR) associated with current smokers was 1.6 (95% confidence interval [CI] = 1.5 to 1.7) and 1.2 (95% CI = 1.1 to 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 (both p for trend <.001). The HR associated with former smokers was 1.2 (95% CI = 1.1 to 1.3) and 0.9 (95% CI = 0.8 to 1.1) for high- and low-frequency hearing loss, respectively. The analysis by quitting years showed a decline in risk of hearing loss after quitting smoking, even among those who quitted less than 5 years before baseline. Smoking is associated with increased risk of hearing loss, especially at the high frequency, in a dose-response manner. The excess risk of hearing loss associated with smoking disappears in a relatively short period after quitting. The prospective association between smoking and hearing loss has not been well studied. To the best of our knowledge, our study is the largest to date investigating the association between smoking and incident hearing loss. Our results indicate that smoking is associated with increased risk of hearing loss in a dose-response manner. Quitting smoking virtually eliminates the excess risk of hearing loss, even among quitters with short duration of cessation. These results suggest that smoking may be a causal factor for hearing loss, although further research would be required to confirm this. If so, this would emphasize the need for tobacco control to prevent or delay the development of hearing loss.