Photo credit: Matthias Zomer from Pexels

by Tricia Glass

When was the last time you were enveloped in quiet? Quiet moments have become a luxury, as have the silent backdrops that make it possible to detect wind rustling treetops or a whispered secret. In cities, suburbs and even in rural settings, man-made sounds – highway traffic, lawn mowers, construction, airplanes passing overhead, freight trains – interrupt our thoughts and conversations; they also wear on our hearing and, according to a recent study, chip away at cognitive function.

Sara Adar, associate professor of epidemiology at University of Michigan School of Public Health worked with a team of researchers led by Jennifer Weuve, associate professor of epidemiology at Boston University, to conduct periodic interviews with 5,227 people age 65 years and older who were participating in a study on aging to assess their orientation, memory, and language. At the same time, the researchers tracked daily noise levels in the neighborhoods where subjects lived for five years prior to the study.

Researchers observed that daily exposure to excessive noise seemed to cause sleep deprivation, hearing loss, increased heart rate, constriction of blood vessels, and elevated blood pressure, all of which are precursors to increased risk of dementia. The participants lived in four adjacent neighborhoods on the south side of Chicago, Illinois, and were evaluated during visits three times a year. About 11% of participants had Alzheimer’s disease and 30% had mild cognitive impairment, which may precede dementia.

Residential noise levels in the study ranged from 51 decibels, the level in a quiet suburb, to 78 decibels, the level near a busy freeway. The study controlled for education, race, smoking, alcohol consumption, neighborhood air pollution levels, and other factors. Researchers found that each 10-decibel increase in community noise level was associated with a 36% higher likelihood of having mild cognitive impairment, and a 29% higher likelihood of having Alzheimer’s disease. “These findings suggest that within typical urban communities in the U.S., higher levels of noise may impact the brains of older adults and make it harder for them to function without assistance. This is an important finding since millions of Americans are currently impacted by high levels of noise in their communities,” says Adar.

Focusing on noise close to home, or community noise, is a shift from prior studies in the United States that have looked at workplace noise and related hearing loss, said Adar.  She added that “while noise-related hearing loss can be a very important issue for workers, we really should be paying closer attention to the stress that community noise can play on our bodies.”

An estimated 5.8 million older Americans have Alzheimer’s disease and 13.8 million cases are expected to nearly triple by 2060. While air pollution, lead and other environmental hazards are also believed to be causes of cognitive decline, community noise is another plausible contributor. There have been few studies mapping a connection, however. This is the first U.S.-based study of its kind.

“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” adds Adar.

Adar and the team are now looking at noise as a risk factor for other health outcomes like hypertension, and they are reproducing their findings in other populations. “The hope is that establishing a stronger base of evidence in the United States may help to inform our local policy makers,” Adar says. “Further down the road, I’d like to study the effectiveness of different interventions to lower noise exposures and improve health in the United States.”

Tricia Glass is a writer, climate activist and leader of Sustainable Wellesley.