Older people with hearing loss are at a much greater risk for developing dementia over time than those who can hear well, according to a study by researchers at Johns Hopkins University School of Medicine and the National Institute on Aging.
The research could lead to new ways of warding off dementia, a problem that affects millions of people around the world and brings with it heavy societal burdens, say the researchers; even something as simple as a hearing aid could help postpone or prevent dementia in some cases.
“Researchers have looked at what affects hearing loss, but few have looked at how hearing loss affects cognitive brain function,” said study leader Frank Lin, M.D., Ph.D., assistant professor in the Division of Otology at Johns Hopkins University School of Medicine.
“There hasn’t been much crosstalk between otologists and geriatricians, so it’s been unclear whether hearing loss and dementia are related.”
The link between hearing loss and dementia is still unclear, but researchers suggest the two conditions may share a common pathology or that the long-term stress of struggling to decode sounds may exasperate the brains of these individuals, leaving them more susceptible to dementia.
Another suggestion is that the individual with hearing loss begins to avoid social activities, a known risk factor for dementia and other cognitive disorders.
For the study, researchers used data from the Baltimore Longitudinal Study on Aging (BLSA). The BLSA, part of the National Institute on Aging, has been following various health factors in thousands of individuals for decades.
The research focused on 639 people whose hearing and cognitive skills had been tested between 1990 and 1994 as part of the BLSA. About one-fourth of the participants had some hearing loss at the beginning of the study, but none had dementia.
The volunteers were then given a follow-up examination every one to two years; by 2008, 58 of them had developed dementia. Study participants who already had hearing loss at the beginning of the study were far more likely to develop dementia by the end.
Compared with normal hearing participants, those with mild, moderate, and severe hearing loss had twofold, threefold, and fivefold the risk of developing dementia over time. In fact, the greater the hearing loss, the higher the risk of developing the disease.
Lin adds that even after age, sex, race, diabetes and high blood pressure were taken into account, dementia and hearing loss were still strongly connected.
“A lot of people ignore hearing loss because it’s such a slow and insidious process as we age,” Lin says. “Even if people feel as if they are not affected, we’re showing that it may well be a more serious problem.”
The study is published in the February Archives of Neurology and was supported by the intramural research program of the National Institute on Aging.