Sleep. Image unrelated to the article. (123rf)
Sleep. Image unrelated to the article. (123rf)

Those who habitually leave the TV or a night light on while sleeping should take note. New research has found that greater exposure to light at night may bring about changes in the structure and function of the heart.

Researchers at Tulane University analyzed the link between nighttime light exposure and changes in heart structure, publishing their findings in the journal European Heart Journal, the UK's Sun reported Wednesday (local time).

The team had 11,071 adults wear a wrist device fitted with a light sensor for a week to measure their nighttime light exposure. About three years later, the participants underwent cardiac MRI scans, and the researchers compared heart structure and function according to the level of light exposure.

The results showed that people exposed to more than 3 lux of light at night exhibited adverse changes in heart structure and function. Those with the highest exposure had thicker walls in the left ventricle, which reduced its internal chamber space. Their heart muscles also became less flexible, showing early signs of cardiac dysfunction.

The researchers described this as "cardiac remodeling," a phenomenon in which the heart's structure and function change in response to chronic stress or damage to the heart.

"This is the first study to show that nighttime light exposure is associated with changes in heart structure," said Lu Qi, the Tulane University professor who led the research.

"Changes in heart structure and function typically emerge as a response to chronic stress or damage to the heart," Lu said. "This is how our bodies adapt to stress, but it can ultimately weaken the heart and lead to heart failure."

The researchers recommended sleeping in as dark an environment as possible at night. A sleep environment is generally recommended to stay below 1 lux of brightness, as anything brighter can disrupt deep sleep. The study found that nighttime light exposure above 3 lux was linked to changes in the heart.

The researchers also stressed that reducing nighttime light exposure should be considered, at both the clinical and policy level, as one way to help prevent cardiovascular disease. "Light pollution at night has emerged as a new risk factor for cardiovascular disease," they said. "This suggests that clinicians and policymakers should consider reducing nighttime lighting exposure as one potential strategy for preventing heart disease."


bbo@heraldcorp.com