Increased dietary intakes of vitamin A and vitamin E are significantly associated with a reduced risk of the prevalence of age-related hearing loss, according to the first population-based study of the link between antioxidants intake and hearing loss from Australia.
The “Blue Mountains Hearing Study”, a cross-sectional and five-year longitudinal analysis included 2,956 participants aged >50 years who were examined between 1997–9 and 2002–4 to assess the link between dietary and supplement intakes of antioxidants and the two parameters prevalence and five-year incidence of measured hearing loss in men as well as in women (1). The authors measured and defined age-related hearing loss as the pure-tone average of frequencies 0.5, 1.0, 2.0 and 4.0 kHz >25 dB HL. They collected the dietary data in a semi-quantitative food frequency questionnaire and calculated the intakes of antioxidants: the carotenoids ?carotene, ?carotene, ?cryptoxanthin, lutein, zeaxanthin and lycopene as well as the vitamins A, C and E and the minerals iron and zinc. Their research was based on the postulation that reactive oxygen species may damage the section of the inner ear associated with hearing. Therefore, they hypothesised that “dietary incorporation of antioxidants might benefit aging individuals in preserving audio cells ... and thus could reduce the hearing loss associated with age”. Hearing impairment is the most frequent sensory deficits around the globe. The statistics from the World Health Organization show that more than 270 million individuals worldwide are affected. Age related hearing loss (presbycusis) is the most prevalent inner ear or auditory nerve disorder. About 30–35% of adults between the ages of 65 and 75 years have a hearing loss and half of those aged over 85 suffer from significant hearing loss.
According to findings of the study, dietary antioxidant intake was not associated with the five-year incidence of hearing loss. But increased intake of vitamin E was associated with a 14 % reduction in the likelihood of suffering from prevalent hearing loss. And the participants in the highest quintile of dietary vitamin A intake had a risk reduction of 47% of having moderate to severe hearing loss (>40 dB HL) compared to the lowest quintile of intake. In contrast, the authors were not able to show that combined intakes of antioxidants reduced the prevalence of hearing loss. Pointing out some of the study’s limitations, the researchers remark that there were “relatively small numbers of incident cases of hearing loss” and that “the duration of follow-up is short and the cohort is relatively old”. They recommend that further prospective studies with larger number and longer follow-up and high quality randomized controlled trials of long duration “to determine whether auditory benefits are derived from treatment with antioxidants”.