Light during sleep linked to conditions that harm the heart

Older adults exposed to light while sleeping at night were more likely to have obesity, high blood pressure, and diabetes than adults who slept in darkness, a new study finds.

The study included 552 adults ages 63 to 84 who were part of the Chicago Healthy Aging Study. In addition to being assessed for factors that raise heart disease risk (such as high blood pressure and diabetes), they all wore devices that measured the amount of light in their bedrooms over a week. Fewer than half of the participants consistently had a five-hour stretch of complete darkness per day. The rest were exposed to some light even during their darkest periods (usually in the middle of the night).

These observational findings cannot prove that nighttime light exposure makes obesity and other heart-related risks more likely. However, light during sleep may disrupt the body's internal clock and trigger other changes that affect normal metabolism, the authors noted. The findings were published online June 22, 2022, by the journal Sleep.

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