Sleeping with the lights on may increase risk of heart disease

Many people have small habits before bed to help them fall asleep faster and sleep more soundly, but be careful, as some habits may actually harm your health. Foreign scientists, after nearly ten years of follow-up research, discovered that one common sleeping habit can significantly increase the risk of various heart diseases, with the likelihood of myocardial infarction, or heart attack, potentially rising by 47 percent.

One Sleeping Habit Increases Risk of Heart Disease; Study Reveals 47pc Higher Myocardial Infarction Risk

Nighttime light exposure disrupts circadian rhythms and is a known potential risk factor for cardiovascular disease. Several sleep medicine experts from the UK, USA, and Australia conducted a 9.5-year follow-up study involving 88,905 participants from the UK Biobank to understand the association between different levels of nighttime light exposure and the incidence of various cardiovascular diseases. The findings were published in JAMA Network Open.

Does Sleeping with the Lights On Increase Risk of Stroke/Myocardial Infarction?

In the study, participants wore light sensors on their wrists to record light exposure 24 hours a day. Nighttime was defined as 12:30 AM to 6:00 AM. The results found that compared to those who slept in dimmer environments:

• People who slept in moderately lit, brighter, and the brightest environments had their risk of developing coronary artery disease increased by 12 percent, 20 percent, and 32 percent respectively.
• Their risk of experiencing a myocardial infarction increased by 20 percent, 27 percent, and 47 percent respectively.
• Their risk of developing heart failure increased by 15 percent, 21 percent, and 56 percent respectively.
• Those who slept in the brightest environments had a 32 percent higher risk of developing atrial fibrillation and a 28 percent higher chance of stroke compared to those sleeping in dim light.
• The longer one slept in a brighter room at night, the higher the risk of developing cardiovascular disease.

Even after excluding factors like diabetes, hypertension, high BMI, high cholesterol, sleep duration, and shift work, nighttime light exposure was still associated with an increased risk of cardiovascular diseases, except for stroke.

The researchers explained that the phenomenon of higher cardiovascular risk with stronger nighttime light exposure might be related to various functional dysregulations caused by circadian clock disruption. The impacts of a disturbed body clock include:

• Reduced ability to process glucose
• Triggering of Type 2 diabetes
• Inducing a hypercoagulable state of the blood
• Elevated nighttime blood pressure

Long-term, these effects increase the risks of vascular endothelial dysfunction, atherosclerosis, thrombosis, ischemia, and arrhythmias.

However, as this is an observational study, it cannot prove a direct causal relationship between light exposure and cardiovascular disease. The researchers also couldn't determine the source of the light, such as whether it was blue light from electronic devices. 

Nonetheless, the results indicate that nighttime light exposure has significant impacts, suggesting that maintaining lighting habits that do not disrupt the circadian clock long-term can help reduce cardiovascular disease risk.

What Other Sleep Issues Might Increase Heart Disease Risk?

Intensive care doctor Wong Hin previously listed four major sleep habits that increase the risk of diabetes, which included sleeping with the lights on. Diabetes is a significant trigger for cardiovascular disease. Here are the other three sleep problems that make people more prone to diabetes:

1. Insufficient Sleep Duration: If daily sleep time is only five hours, the risk of diabetes significantly increases by 16 percent; sleeping only three to four hours per day increases the risk by up to 41 percent. Only getting a full seven hours of sleep daily reduces the risk of diabetes.
2. Snoring During Sleep: Sleep apnea patients experience increased blood sugar and insulin resistance, raising their risk of developing diabetes by 31 percent.
3. Going to Bed Late and Waking Up Late: The risk of diabetes for early birds is 27 percent, while for night owls, the risk more than doubles, reaching as high as 56.8 percent. The likely reason is that circadian rhythm disruption disturbs the body's endocrine balance, triggering diabetes.