As the baby boom generation ages, the prevalence of cognitive impairment is expected to climb dramatically. Researchers are therefore anxious to discover causes and risk factors for dementia and use the knowledge to mitigate the coming storm. In an effort to examine the relationship between cognitive impairment and hearing loss, which studies have linked, researchers analyzed data from the Health, Aging, and Body Composition study.

Adults 70 to 79 years of age were recruited in 1997 and 1998. The analysis involved 1,984 subjects from the original cohort who showed no evidence of cognitive impairment at baseline. Five years into the study, participants underwent audiometric testing; the Modified Mini-Mental State Examination (3MS) and the Digit Symbol Substitution (DDS) test were used to evaluate cognitive function. Hearing loss was defined as a pure-tone average higher than 25 decibels; at baseline, 1,162 had hearing loss: 66% had mild loss, 33% had moderate loss, and 1% had severe loss. Cognitive function was monitored in year 5, too, and then again in years 8, 10, and 11.

After adjustment for demographic and cardiovascular risk factors, cognitive scores among those with hearing loss were lower even at baseline than among those with normal hearing. Overall, adults with hearing loss at baseline had a 41% greater annual rate of decline on the 3MS and a 32% greater decrease on the DSS test than participants without hearing loss, and the rate of decline increased according to the magnitude of the hearing loss. Subjects with hearing loss but no cognitive impairment at baseline had a 24% higher risk of incident cognitive impairment during the study period than adults with normal hearing.

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