A Japanese study finds low-level light exposure at night can be associated with depressive symptoms in elderly adults.

Researchers used light meters to measure nighttime light exposure in the bedrooms of more than 800 elderly Japanese adults over two years. They found 73 developed depressive symptoms during the study follow-up, with a correlation between light at night (LAN) and depressive symptoms.

“These results indicated that exposure to LAN in home settings was independently associated with subsequent depression risk in an elderly general population,” researchers reported in the American Journal of Epidemiology.

While they didn’t study how light exposure relates to depression, the team said it might be driven by sleep disturbances that influence how the body regulates melatonin. Previous studies have indicated that minimal light exposure at night increases depression risk in nocturnal and diurnal mammals.

Compared with seniors who averaged less than 5 lux of light in their rooms, those with more light had a much higher depression risk, even when adjusting for hypertension and diabetes.