Dim lighting during sleep may pose a hidden risk to heart health

A new study reveals that exposure to a small amount of light during sleep may change the shape and function of the heart muscles, increasing the risk of heart disease in the future. “Light pollution has emerged as a new risk factor for cardiovascular disease,” said Dr. Lu Qi, lead author of the study, HCA Regents Distinguished Chair, and professor and director of the Center for Obesity Research at Tulane University in New Orleans.

“Our findings, along with evidence from other studies, suggest that limiting light exposure at night should be one potential strategy that clinicians and policymakers consider to prevent heart disease,” Chi added in a statement. In order to get good sleep, experts said that the lighting level in the bedroom should not exceed 1 lux, meaning that the room should be largely dark.

Lux is a unit of light intensity within the International System of Units, and a level of 3 lux is approximately equivalent to moonlight or light seeping under a closed bedroom door. In this study, researchers found that the walls of the heart muscle in people who were exposed to more than 3 lux of light during sleep became thicker, which reduced the heart's efficiency in pumping blood.

According to the study, the degree of damage increases the more light the bedroom becomes. Additional light sources may include the glare of a face-up smartphone, the light of a digital alarm clock, or light pollution from outside.

The study was published in the European Heart Journal on Wednesday, and analyzed the sleep of more than 11,000 people without cardiovascular disease, who were participants in the UK Biobank study, a biomedical database that includes genetic and health data for about 500,000 people in the United Kingdom. All study participants wore a device on the wrist for 7 days to measure light levels during the night.

After 3 years, each of them underwent a cardiac MRI to examine the structure and function of the heart. Compared with people who were not exposed to light at night, sleeping with light exceeding 3 lux resulted in thickening of the walls of the heart's left ventricular chamber, reducing the space within it.

The ability of the heart muscle to expand during the heartbeat also decreased, which is an early sign of cardiac dysfunction. Additional damage was observed in two other chambers of the heart.

Reshaping the heart muscle is known as “cardiac remodeling,” said Dr. Andrew Freeman, director of cardiovascular disease prevention and wellness at National Jewish Health in Denver. Freeman, who was not involved in the study, pointed out that “we do not want the heart muscle to become thicker.

All of these things seem to happen with exposure to excess light, and perhaps poor sleep quality.” For his part, Chi said that between 24% and 49% of the effect on the heart is due to short sleep duration of less than 5 or 6 hours, which is “a direct result of exposure to light at night.”

Other factors may explain the remaining 51% of risk. Qi pointed to factors such as blood pressure, heart rate, and other factors associated with the risk of cardiovascular disease such as stress and biological changes.

Carl Lawrence, a lecturer at the Institute of Pharmaceutical Sciences at King's College London, said the study had some limitations. For example, a one-week test is too short to measure overall light exposure.

Additionally, using a light sensor on the wrist “does not give an accurate estimate of the amount of light reaching the eye, and may lead to over- or underestimation.” Lawrence explained to Ofoq News, "Linking this to heart examinations conducted after 3 years seems somewhat exaggerated."

Further studies will be needed to prove a causal relationship.” Limiting exposure to light at night Experts have indicated that blocking light in the bedroom is relatively easy.

Thick curtains, light-blocking curtains, or blinds can be placed on each window. Corridor lights should also be turned off at night, and if light still leaks from under the door or from the edges of windows, try using strips or foam materials to block the light, which may be sold as draughts or weather strippers.

If low levels of light continue to creep into the room, try using a sleep mask. Bedside reading lamps can be chosen with warm white, dark amber or red light, and their effective color temperature is low or close to zero.

If you need a night lamp, make sure it is dim and at ground level, and choose a lamp in red or brown tones.