If you've spent any time around older people you know that hearing loss is very common. As Rick and I discuss on PodMed this week, most adults over the age of 70 have some degree of hearing loss, and more distressingly, the majority of them remain unevaluated and untreated. Now comes a Johns Hopkins study by Frank Lin, in this issue of JAMA Internal Medicine (formerly Archives of Internal Medicine) linking hearing loss and cognitive decline, another common and burgeoning issue for aging folks worldwide, and those who love and care for them. Indeed, as estimates indicate a public health crisis regarding Alzheimer's disease and other forms of dementia, this may be the most important implication of the hearing/cognition association. So what did the study do?
Lin and colleagues studied almost 2000 adults with a mean age of 77.4 years who were enrolled in the Health ABC Study, which began in 1997-1998. At baseline subjects underwent a Modified Mini-Mental State Examination (3MS)and had an audiometric test in year 5 of the study. In years 5,8, 10 and 11 cognitive testing was repeated with the addition of the Digit Symbol Substitution test to the 3MS. Annual rates of decline for those with hearing loss on these two measures were accelerated compared with those who did not experience hearing loss, for an overall increased risk for cognitive decline of 24% among subjects whose hearing was compromised. There was a linear association between severity of hearing loss and rate of cognitive decline.
Well. As Rick points out in the podcast, we all know people who are perfectly fine with regard to cognition but whose hearing is sketchy, so there are plenty of examples to disprove an inextricable relationship. Does this mean we should suspect cognitive impairment in everyone with hearing loss? No, but it does suggest a role for hearing assessment in people as they age.
What does this association tell us about causality? According to Frank Lin, a couple of hypotheses are worth considering: perhaps a common pathological mechanism underpins both some forms of dementia and loss of hearing. Does accelerated hearing loss cause people to voluntarily isolate themselves from social interaction, known to be protective with regard to preservation of cognitive abilities, thus placing themselves at risk? Lin also cites MRI studies showing that people with hearing loss must recruit more brain power to interpret garbled auditory signals, and this may impair cognition. Clearly, one part of the answer relies on the efficacy of intervention. Do people who are fitted with hearing aids and taught to use them properly stave off dementia? Unquestionably a huge and lengthy trial, but one with profound public health implications for our aging population around the globe.
Other studies this week include another in JAMA Internal Medicine on chicken soup and melamine exposure, several in JAMA on 30 day readmission rates and what they might mean, and in Annals of Internal Medicine the recommendations from the USPSTF on screening for intimate partner violence and violence against elders and other at risk populations. Until next week, y'all live well.
Hearing Loss and Cognition,8 Comments