Inadequate levels of folic acid were significantly associated with age-related hearing loss, study findings published in the Otolaryngology Head and Neck Surgery.

In 126 healthy Nigerian men and women older than age 60 years, low folic acid contributed significantly to the loss of high-frequency hearing. Those with normal pure tone average (PTA) in the speech frequencies had an average serum folate value of 412.3 nmol/L + 17.6 nmol/L. But in those with hearing loss, average serum folate was 279.1 + 17.2. In the high frequencies, average serum folate was 426.3 + 17.6 for those with normal PTA but 279.14 + 17.12 for those with hearing loss.

Hearing loss also appears to be a consequence of passive smoking, according to another study by David A. Fabry and colleagues, published online in Tobacco Control. Previous research indicates that smokers are more likely to lose hearing, but the latest analysis shows that nonsmokers with notable blood levels of cotinine—a constituent of tobacco smoke—may suffer the same fate.

Almost one in 10 never-smokers (8.6% of the group) had low- to mid-frequency hearing loss and one in four had high-frequency hearing loss. Former smokers were more likely to have impaired hearing, with 14% experiencing low- to mid-frequency hearing loss and more than 46% suffering high-frequency hearing loss.