Nighttime light exposure linked to increased stroke risk, study finds

Research reveals that exposure to bright artificial light at night might increase the risk of stroke and other cerebrovascular diseases, according to the latest findings published in the "Stroke" journal.

A study led by scientists from Zhejiang University in China, involving nearly 30,000 participants, has shown that intense nighttime light exposure correlates with a heightened risk of serious cerebrovascular incidents. The study also highlights that air pollution may have similar adverse health effects.

While bright outdoor lighting enhances visibility and safety at night, the researchers argue that the current extent of such lighting is excessive. This overuse has led to about 80% of the global population living in areas affected by light pollution, with potential negative impacts on human health.

Past research has linked artificial nighttime light exposure with the development of cardiovascular diseases. It's now emerging that light pollution could also harm brain health.

Dr. Jian-Bing Wang, a contributing author, notes, "Significant strides have been made in reducing traditional cardiovascular risk factors, such as smoking, obesity, and type 2 diabetes. Yet, environmental factors must also be considered in our ongoing efforts to lower the worldwide disease burden."

In a comprehensive review covering over 28,000 adults in China, Dr. Wang and his colleagues mapped light pollution using satellite imagery to assess exposure to outdoor nighttime light. They then correlated this data with hospital and death records of stroke cases over a six-year period. The artificial lighting types included in the study were fluorescent, incandescent, and LED.

The findings revealed that, during the study period, 1,278 participants developed cerebrovascular diseases, including 777 ischemic strokes and 133 hemorrhagic strokes. Individuals most exposed to nighttime lights had a 43% higher risk of cerebrovascular disease than those with minimal exposure.

The study also discovered that high exposure to fine particulate matter PM2.5, mainly from combustion sources like gasoline, diesel, or wood, carried a 41% greater risk of cerebrovascular events. PM10 particles, generally originating from dust and smoke, increased the stroke risk by 50%.

Meanwhile, those most exposed to nitrogen oxide faced a 31% higher risk of cerebrovascular disease compared to the least exposed participants.

"Our findings indicate that excessive nighttime light exposure outdoors may be a risk factor for cerebrovascular diseases," Dr. Wang remarks. "Thus, we recommend that people, especially those in urban areas, minimize their exposure to safeguard against its potentially harmful effects."

The authors explain the potential mechanism behind their findings: constant exposure to bright nighttime light suppresses melatonin production, a sleep-promoting hormone, disrupting the body's circadian rhythm and leading to sleep disorders. Extensive research has documented that poor sleep quality can significantly worsen cardiovascular health over time.

"To reduce the disease burden from environmental factors like light and air pollution, more effective regulations and preventive strategies are urgently needed, particularly for individuals residing in densely populated and polluted regions," Dr. Wang concludes.