The combined effect of cigarette smoking and occupational noise exposure on hearing loss: evidence from the Dongfeng-Tongji Cohort Study.

Combined effect of cigarette smoking and occupational noise exposure on hearing loss has rarely been evaluated among Chinese population, especially among females. This cross-sectional study was conducted in 11196 participants of Dongfeng-Tongji cohort study. Smoking status was self-reported through questionnaire and occupational noise exposure was evaluated through workplace noise level and/or the job titles. Hearing loss was defined as a pure-tone mean of 25 dB or higher at 0.5, 1, 2, and 4 kHz in both ears. Compared with participants without occupational noise exposure, the risk of hearing loss was significantly higher for noise exposure duration ≥20 (OR = 1.45, 95%CI = 1.28-1.65). The association was particularly evident among individuals who were males (OR = 1.74, 95%CI = 1.45-2.08) and aged ≥ 70 (OR = 1.74, 95%CI = 1.30-2.33). Similarly, the risks increased with the increasing of pack-years in males and all age groups except for those aged <60. As to the combined effect, the hearing loss risk was highest for noise exposure duration ≥20 and pack-years ≥25 (OR = 2.41, 95%CI = 1.78-3.28), especially among males (OR = 2.42, 95%CI = 1.74-3.37) and those aged ≥70 (OR = 2.76, 95%CI = 1.36-5.60). Smoking may be an independent risk factor for hearing loss. And it may synergistically affect hearing when combined with occupational noise exposure, especially among males and older participants.