Obesity and risk of hearing loss in the middle-aged and elderly: a national cohort of Chinese adults.

BACKGROUND: The relationship between obesity and hearing loss among the middle-aged and older population remained unclear. Moreover, few studies have focused on the impact of gender on this association. METHODS: This cohort study extracted the data from the China Health and Retirement Longitudinal Study, a national survey of adults aged 45 years or over. Waist circumference was categorized into three groups: normal, pre-central obesity, and central obesity. We classified BMI into four categories: underweight, normal weight, overweight, and obese. The primary endpoint was the incidence of self-reported hearing loss. RESULTS: Of the 14,237 participants, 1972 incidents of hearing loss were identified during a median 6.9 years of follow-up. The cumulative incidence of hearing loss was 13.9% (95% CI 13.3% -14.4%). Our study showed that central obesity was significantly associated with hearing loss (HR 0.84, 95%CI 0.75-0.94), and this relationship was more prominent in males (HR 0.76, 95%CI 0.63-0.91). Among male participants, the underweight group was at the highest risk of hearing loss (HR 1.39, 95%CI 1.08-1.79). Compared with the normal weight group, the adjusted HR for hearing loss in the obese groups was 0.69 (95%CI 0.51-0.94) among men. Among female participants, only the overweight group had a lower risk of hearing loss than the normal weight group (HR 0.83, 95%CI 0.71-0.96). CONCLUSIONS: Being overweight and obese were significantly associated with a decreased risk of hearing loss, whereas being underweight was associated with an increased risk of hearing loss.