Folate Supplementation and Age-Related Hearing Loss

Everyone knows that elderly people hear less well than young people and that men hear less well than women, albeit with considerable variability across individuals. Although noise, infection, head trauma, and ototoxic drugs cause some variation, most hearing loss in the developed world is simply “age-related.” In other words, nothing in the patient history or objective findings explains why a patient is hearing-impaired. Age-related hearing loss is sensorineural (it affects the inner ear rather than the outer or middle ear) and is associated with loss of hair cells and other cellular elements in the cochlea. Age-related threshold elevations (termed as such because the loudness of a just-audible tone increases with advancing age) occur first at the highest frequencies that young humans can hear (up to 20 kHz) and begin in early adulthood: High school students can download to their cellular phones ultra high-frequency ring tones that are inaudible to most of their teachers. In later years, hearing loss increases and affects lower frequencies. Age-related hearing loss is not only progressive, it accelerates; Threshold differences between 70-year-old people and 60-year-old people are larger than those between 60-year-old people and 50-year-old people. Age-related hearing loss has a substantial degree of high heritability (1, 2) and has been (at least until now) considered refractory to medical or surgical treatment.

Fortunately, age-related hearing loss is typically not noticeable in everyday life until late middle age, when threshold elevations begin to markedly affect the “speech frequencies” (most often defined as extending from 500 Hz to about 3 or 4 kHz …