Higher levels of noise may increase dementia risk in older adults

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Alzheimer’s disease and other forms of dementia affect millions of older adults in the US—but not equally. Past research has identified risk factors including genes, education, racism, and air pollution, and a growing number of studies now point to noise as another influence on the risk of dementia.

Now, a new study co-led by a School of Public Health researcher finds that 10 decibels more daytime neighborhood noise is associated with 36 percent higher odds of mild cognitive impairment and 30 percent higher odds of Alzheimer’s disease.

Published in Alzheimer’s & Dementia, the journal of the Alzheimer’s Association, the study is the first of its kind in the US.

“We remain in early stages in researching noise and dementia, but the signals so far, including those from our study, suggest we should pay more attention to the possibility that noise affects cognitive risk as we age,” says study first author Jennifer Weuve, associate professor of epidemiology.

“If that turns out to be true, we might be able to use policy and other interventions to lower the noise levels experienced by millions of people,” she says, noting that the US Environmental Protection Agency last set community noise level guidelines back in the 1970s. “Those guidelines were set to protect against hearing loss. Many of our participants were exposed to much lower levels.”

The study included 5,227 older adults participating in the Chicago Health and Aging Project (CHAP), which has followed a total of 10,802 individuals 65 years old or older living on the South Side of Chicago since the 1990s. Participants were interviewed and their cognitive function tested in three-year cycles.

For neighborhood noise levels, the researchers used a Chicago-area model from a previous study. That study gathered samples of A‐weighted noise (the important frequencies for human hearing) at 136 unique locations during daytime, non–rush hour periods between 2006 and 2007, then used these samples combined with data on other geographic factors—including land use and proximity to roadways and bus stops—to estimate noise levels in any location of the Chicago area. (Follow-up sampling found that the model was still accurate in CHAP participants’ neighborhoods in 2016.)

In the new study, the researchers analyzed the relationship between CHAP participants’ cognitive function and the noise levels in the neighborhoods where they had lived over a 10-year period. They also examined how date of birth, sex, race, education level, household income, alcohol intake, smoking status, physical activity, and neighborhood socioeconomic status factored into this relationship.

They found that, after accounting for these other factors, study participants living with 10 decibels more noise near their residences during the daytime had 36 percent higher odds of having mild cognitive impairment and 30 percent higher odds of having Alzheimer’s disease.

The only factor that they found affected this relationship was neighborhood socioeconomic status, with residents of lower socioeconomic status neighborhoods showing the strongest association between noise level and odds of Alzheimer’s or mild cognitive impairment.

“These findings suggest that within typical urban communities in the United States, higher levels of noise may impact the brains of older adults and make it harder for them to function without assistance,” says study senior author Sara D. Adar, associate professor of epidemiology at the University of Michigan School of Public Health, Ann Arbor.

“This is an important finding since millions of Americans are currently impacted by high levels of noise in their communities,” she says. “Although noise has not received a great deal of attention in the United States to date, there is a public health opportunity here as there are interventions that can reduce exposures both at the individual and population level.”

The study was supported by grants from the Alzheimer’s Association and the National Institute on Aging. The other co-authors are: Jennifer D’Souza and Carlos F. Mendes de Leon of the University of Michigan School of Public Health, Ann Arbor; Todd Beck and Denis A. Evans of the Institute for Healthy Aging at Rush University in Chicago; Joel D. Kaufman of the University of Washington School of Public Health; and Kumar. B. Rajan of the University of California, Davis.

Source: Boston University

Original Study DOI: 10.1002/alz.12191