Sunlight exposure may be a risk factor of hearing impairment: a community-based study in Japanese older men and women

Oxidative stress is an important factor in the pathology of age-related hearing loss. Recent animal studies have reported that ultraviolet radiation in sunlight is related to systemic induction of oxidative stress. Chronic sun exposure leads to photodamaged skin, which is manifested as facial skin wrinkling and hyperpigmentation. We hypothesized that sunlight exposure, as assessed by the severity of facial skin photodamage, might be associated with hearing impairment through an oxidative stress mechanism. To examine this, we performed a cross-sectional analysis by using the baseline data from a community-based cohort study of older Japanese.

A total of 805 residents (342 men and 463 women) aged 65 years or older living in Kurabuchi Town, Gunma prefecture, Japan, were examined between 2005 and 2006. Facial skin condition was quantified by image analysis of standardized facial images. Hearing impairment was defined as a failure to hear a 30-dB signal at 1 kHz and a 40-dB signal at 4 kHz in the better ear in pure-tone audiometric tests.

In men, facial wrinkle was positively associated with hearing impairment (for highest vs lowest: multivariate-adjusted odds ratio, 2.16; 95% confidence interval, 1.00-4.66; p for trend = .01). Stratified analysis by age, educational level, smoking status, sunscreen or foundation use, and diabetes showed results similar to those for men as a whole. This association was particularly pronounced in men with the low levels of antioxidants and without occupational noise exposure. We observed no apparent association in women.

The results support the hypothesis that chronic sun exposure is a risk factor of hearing impairment.