Age-related hearing loss, methylmalonic acid, and vitamin B12 status in older adults.

Hearing loss has been associated with poor vitamin B12 status in some, but not all studies. This study examined a possible relationship between age-related hearing loss and poor B12 status in 93 older adults using different indices of B12 status. Hearing loss was defined as pure-tone average threshold > 25 decibel hearing level. Participants with methylmalonic acid (MMA) > 271 nmol/L at baseline received 1,000 g/d, and those with MMA < or = 271 nmol/L were randomly assigned to receive 0, 25, or 100 microg/d of B12. In a series of logistic regression analyses, compared with participants with normal hearing, those with impaired hearing had a significantly higher serum mean MMA concentrations in the best and the worst ears and a higher prevalence of elevated MMA (> 271 nmol/L) in the worst ear only. Thus, elevated MMA concentration may be associated with hearing loss in older adults. However, short-term B12 supplementation was unrelated to improvements in hearing status in B12-deficient individuals.