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 risk of dementia.

“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 first author Jennifer Weuve, associate professor of epidemiology at Boston University’s School of Public Health.

“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. Researchers interviewed participants and tested their cognitive function 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.

Read the full article about Alzheimer's research by Michelle Samuels at Futurity.