Photo credit: Alyssa L. Miller licensed under CC BY 2.0
by Daniel Fink, MD, Chair, The Quiet Coalition
The most common definition of noise is “noise is unwanted sound.” We at The Quiet Coalition recently came up with a new definition: noise is unwanted and/or harmful sound. The specific evidence-based sound levels associated with adverse health and public health hazards are summarized in my article in Acoustics Today, “Ambient Noise Is ‘The New Secondhand Smoke.'”
Sounds as low as 30-35 A-weighted decibels* can disrupt sleep. Uninterrupted sleep is important for both daily function and health. Nighttime noise is increasing, caused by aircraft noise, road traffic noise, emergency vehicle sirens, horn-based alerts, and sounds from clubs, bars, and concerts, with the specific noise source(s) depending on where people live.
It has been known since 2013 that sleep is necessary for cellular cleaning functions in the brain. A new study, reported by NPR, extends this research to Alzheimer’s disease. It has been known for some time that poor sleep is associated with Alzheimer’s disease, and patients with Alzheimer’s disease don’t sleep well. The new study shows that there are waves of cerebrospinal fluid occurring every 20 seconds during sleep, preceded by electrical activity. The electrical waves appear as slow waves on an EEG. Those with Alzheimer’s disease have fewer slow waves on their EEGs.
I have only read the NPR report, not the underlying article in Science, and I’m not 100% sure the cause-effect relationship between sleep disruption and Alzheimer’s has been clearly established. Which really came first, the sleep problems or the Alzheimer’s disease? Nonetheless, the study underscores the importance of a good night’s sleep.
Noise pollution is a public health problem. And one wonders if the increase in Alzheimer’s disease is due in part to increased nighttime noise levels.
*A-weighting adjusts sound measurements to reflect the frequencies heard in human speech.
