- Researchers have found that sleeping in even a small amount of light can affect health.
- The findings suggest that light exposure during sleep is linked to an increased risk of obesity, diabetes and high blood pressure in older adults.
- An earlier laboratory study by the same researchers showed that the detrimental effects are not limited to older people.
A study from the Feinberg School of Medicine at the Northwestern University at Chicago explore the link between light exposure during sleep and health risks.
The research serves as a warning to many people who live in industrialized countries where light tends to be ubiquitous.
Sleeping while exposed to any type of light, even dim light, is linked to an increased chance of obesity, diabetes and hypertension (high blood pressure) in older adults, according to the study.
The corresponding author of the study, Dr Minjee Kimof Northwestern Medicine Feinberg School of Medicine, said in a news release: “Whether it’s from the smartphone, leaving the TV on at night, or light pollution in a big city, we live among an abundance of artificial light sources that are available 24 hours a day.”
“It appears that even a small amount of light has a noticeable effect on our body’s response,” Dr. Kim told Medical NewsToday.
It’s not just the elderly, it’s health that can be affected by not sleeping in deep darkness
“In a previous study conducted by our group, even one night of dim light exposure during sleep increased heart rate and blood glucose in healthy young adults who were taken to a sleep lab for an overnight experiment,” explained Dr. Kim .
Dr. Jonathan Cedernaesa sleep expert at Uppsala University in Sweden, who was not involved in either study, told MNT:
“The fact that this is seen in older people may represent the more cumulative effects of such a mechanistic relationship, meaning that the adverse cardiometabolic effects of nighttime light exposure may become more apparent over time (i.e. , at a later age, if such a lifestyle or exposure pattern is maintained for years or decades)”.
The study was published in the journal Oxford Academic SLEEP.
The study lists three possible mechanisms behind the disturbing effect of light during sleep:
- Light is the main synchronizer of the circadian rhythm or body clock. Light during sleep can alter this rhythm and thus any physiological process related to the clock.
- The pineal gland produces and secretes melatonin, the “hormone of darkness,” during dark periods. Light can reduce the metabolic and circulatory function of melatonin with its antioxidant, anti-inflammatory and vasodilatory properties. Lower melatonin levels correlate with an increased risk of diabetes in women and an increased risk of hypertension in young women.
- During healthy sleep, the system responsible for fight or flight responses relaxes, which slows the body’s heart rate and breathing into a parasympathetic state.
When asked if more light equates to a higher risk of disease, Dr. Kim responded:
“We found a trend towards a stronger association (a higher rate of obesity and diabetes) with higher light exposure at night. We hope to confirm this finding with future studies in a broader age range.”
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