Adverse Effect of Nighttime Light on the Heart

What role does light exposure play in our health? I’ve already written one post about our relationship to light. We know that light exposure has a negative impact on sleep, but other than that widely studied relationship, further information is hard to come by. A recent study looked at one area impacted by light, the cardiovascular system. Of particular concern was looking for an adverse effect of nighttime light on the heart.

The Study

The study included 11,071 adults without cardiovascular disease. They wore a light monitor on their wrists for 7 days. The study measured exposure of light during the night, during the day, and duration of sleep. After approximately 3 years the participants had an MRI performed to measure several health factors. These 11,071 participants were then included in a follow-up of over 70,000 people to look for the long-term health outcomes over 7.9 to 9.5 years.

The Findings

The study found that higher exposure to nighttime light was associated with several different heart findings through the MRI. These include increased mass of the left ventricle, greater heart wall thickness, and lower output of blood per contraction of the heart. Also found was a larger right ventricle and decreased atrial volumes of blood.

These physical findings translate to several increased risks. First, a 29% higher risk for heart failure. Second, a 15% higher risk for atrial fibrillation. Third, a 24% higher risk for myocardial infarction. Fourth, a 33% higher risk for stroke. Finally, a 26% higher risk for cardiovascular mortality. In addition to light exposure at night, shorter sleep duration accounted for 24-49% of the association to adverse cardiac MRI findings.

The Conclusion

In conclusion, it is clear that there is an adverse effect of nighttime light exposure on the heart. Where cardiac risk already exists or if there is a family history of cardiac issues, it is important to evaluate all cardiac risk factors. Simple steps can lower light exposure risks to the heart. Read about our relationship to light here and tips for improved sleep here. The main takeaway is to lower nighttime light exposure. Decrease screen time after the sun goes down. Dim the lights after dark. When it is time to sleep, sleep in a dark room. Simple steps can help limit the adverse effect of nighttime light on the heart.