Dim Light During Sleep May Pose a Hidden Risk to Heart Health

- A new study has revealed 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. Dr. Lou Chi, the lead author of the study, who holds the distinguished HCA Regents Chair and is a professor and director of the Obesity Research Center at Tulane University in New Orleans, USA, stated that "light pollution has emerged as a new risk factor for cardiovascular diseases."

Chi added in a statement: "Our results, along with evidence from other studies, suggest that reducing exposure to light at night should be one of the potential strategies that doctors and policymakers consider for the prevention of heart disease." To achieve good sleep, experts say that the lighting level in the bedroom should not exceed 1 lux, meaning the room should be largely dark.

Lux is a unit of measurement for illuminance in the International System of Units, and a level of 3 lux is approximately equivalent to moonlight or light seeping from under a closed bedroom door. In this study, researchers found that the walls of the heart muscle in individuals exposed to more than 3 lux of light during sleep became thicker, reducing the heart's efficiency in pumping blood.

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

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

After 3 years, each of them underwent cardiac MRI to examine the structure and function of the heart. Compared to individuals who were not exposed to light at night, sleeping in light exceeding 3 lux led to an increase in the thickness of the walls of the left ventricle of the heart, which reduced the space inside it.

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

Dr. Andrew Freeman, director of the cardiovascular disease prevention and wellness department at National Jewish Health in Denver, USA, stated that the remodeling of the heart muscle is known as "cardiac remodeling." Freeman, who was not involved in the study, pointed out that "we do not want the heart muscle to thicken."

It seems that all these issues occur with excessive light exposure, and possibly low-quality sleep." For his part, Chi stated that between 24% and 49% of the impact on the heart is due to the short duration of sleep 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 the risk. Chi pointed to factors such as blood pressure, heart rate, and other factors associated with the risk of cardiovascular diseases such as stress and biological changes.

Karl Lawrence, a lecturer at the Institute of Pharmaceutical Sciences at King's College London, stated that the study had some limitations. For example, a one-week testing duration is significantly short to measure light exposure in general.

Additionally, using a light sensor on the wrist "does not provide an accurate estimate of the amount of light reaching the eye, and this may lead to overestimating or underestimating it." Lawrence explained to Afaaq News that "linking this to heart tests conducted after three years seems somewhat exaggerated.

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

Thick curtains or blackout blinds can be placed to block light, or curtains can be used on every window. The hallway lights should also be turned off at night, and if light continues to seep in from under the door or from the edges of the windows, try using strips or sponge materials to block the light, which may be sold as air draft blockers or weather insulation.

If low levels of light continue to sneak into the room, try using a sleep mask. Bedside reading lamps can be chosen with warm white light or dark amber or red, which have a low or near-zero effective color temperature.

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