- Researchers have found that sleeping with even a tiny amount of light can impact health.
- The results suggest that light exposure during sleep is linked to a higher risk of obesity, diabetes and high blood pressure in older people.
- An earlier laboratory study by the same researchers showed that the adverse effects are not limited to the elderly.
A study from Northwestern University Feinberg School of Medicine in Chicago explores the link between light exposures during sleep and health risks. The research serves as a warning to many people living 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 likelihood of obesity, diabetes and hypertension (high blood pressure) in older people, the study found.
The study’s corresponding author, Dr Minjee Kim, of the Northwestern Medicine Feinberg School of Medicine, said in a press release: “Whether from her smartphone, leaving a TV on at night, or case of light pollution in a big city, we live among an abundant number of artificial light sources available 24 hours a day.”
“It seems that even a tiny amount of light has a noticeable effect on our body’s response,” Dr. Kim said. Medical News Today.
“Previous animal studies and some human studies have suggested a potential association between unwanted light — not enough light during the day, too much light at night — and obesity,” Dr. Kim said.
“There was little data on light exposure patterns in older adults,” Dr. Kim said. “Since older people are already at increased risk of cardiovascular disease, we wanted to know how often older people are exposed to ‘light at night’ [or “LAN”]and whether light at night is correlated with CVD risk factors.
It’s not just the elderly whose health can be affected by not sleeping in deep darkness.
“In a previous study by our group, even overnight exposure to dim light during sleep increased heart rate and blood sugar levels in healthy young adults who were brought into a sleep lab for an experiment. nocturnal,” Dr. Kim explained.
Dr Jonathan Cedernaes, a sleep expert from Uppsala University in Sweden, who was not involved in either study, said DTM:
“The fact that this is observed in the elderly may represent the most cumulative effects of such a mechanistic relationship, meaning that adverse cardiometabolic effects of nighttime light exposure may become more evident over time (c that is, at a later age, if one maintains such a relationship (lifestyle or pattern of exposure over years or even decades).
The study was published in the journal Oxford Academic SLEEP.
Unlike the group’s previous research, the new study observed the actual effects of LAN, tracking the sleep of 552 elderly men and women.
“In the present study, we measured light exposure and sleep in older people (63-84 years) for seven days using a wrist-worn device. Instead of bringing these people elderly in the sleep lab, we collected data from their routine environment,” Dr. Kim said.
They found that less than half of these seniors slept in a darkened room for at least five hours.
“We were frankly surprised to find that more than half of older people slept with some light in night,” Dr. Kim said. “Adults who slept with some light during their sleep period were usually exposed to dim light.”
The researchers found that the likelihood of developing high blood pressure (hypertension) was increased by 74%, obesity by 82% and diabetes by 100%. Participants were also tested for an increased risk of high cholesterol, but no difference was seen.
The study lists three possible mechanisms behind the disruptive effect of light during sleep:
- Light is the primary synchronizer of the circadian rhythm or body clock. Light during sleep can disrupt this rhythm and therefore any clock-related physiological process.
- The pineal gland produces and secretes melatonin, the “dark hormone”, during periods of darkness. Light can reduce the metabolic and circulatory function of melatonin through its antioxidant, anti-inflammatory and vasodilator properties. Lower levels of melatonin are correlated with an increased risk of diabetes in women and an increased risk of hypertension in young women.
- The light can trigger the
autonomic nervous systemsympathetic arm. During healthy sleep, the system responsible for fight-or-flight responses relaxes, slowing 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 replied: ‘We found a trend for a stronger association – higher rate of obesity and diabetes – with brighter exposure at night. We hope to confirm this finding with future studies over a wider age range.
“While we cannot conclude anything beyond the association due to the cross-sectional (“instantaneous”) nature of the study, I encourage everyone to try to avoid or minimize any light at night if possible,” Dr. Kim advised.
“It can be as simple as not using electronic devices near the sleeping area and blocking out light with a sleep mask,” he added.
Still, Dr Kim cautioned: ‘If people need to use a night light for safety, they should try to keep it as close to the ground as possible to minimize light entering their eyes. If they need to use the bathroom at night and walking in total darkness is dangerous, try using dim lights for the shortest time necessary.
It also seems that the color of light a person sleeps in matters.
“I would recommend using an orange or red light to [a] night light on blue light. Amber/red light (longer wavelengths) disrupts our circadian clock in the body less than lights with shorter wavelengths such as blue light,” Dr. Kim explained.
“Some groups are forced to work at night,” added Dr Cedernaes, and have to sleep during the day. “There are also ways to block light (for example, specific filters in eyewear), and further studies may be warranted to establish methods to counteract light exposure… [and] reduce cardiometabolic risks.