Night owls twice as likely to suffer life-threatening heart issues

GOTHENBURG, Sweden — A concerning new study reveals that people who have a tendency to stay up late are at greater risk of suffering a heart attack. Researchers from the University of Gothenburg in Sweden say “night owls” are nearly twice as likely to experience artery calcification compared to those who wake up early.

Artery calcification, or atherosclerosis, is a condition where fatty deposits build up inside the arteries, making it difficult for blood to flow. This disease develops slowly and often goes unnoticed until it leads to serious health issues like:

• Angina (chest pain)
• Blood clots
• Heart attacks
• Strokes

The study involved 771 men and women between 50 and 64, part of a larger population study called the Swedish CArdioPulmonary bioImage Study, or SCAPIS. To measure artery calcification, researchers used computer tomography to examine the heart’s coronary arteries. Participants self-reported their sleep habits, known as their “chronotype,” on a scale ranging from extreme morning to extreme evening types.

Among the 771 participants, those who identified as extreme morning types had the lowest proportion of pronounced artery calcification at 22.2 percent. In contrast, the extreme evening type group showed the highest incidence of severe coronary artery calcification, with a rate of 40.6 percent.

“Our results indicate that the extreme evening chronotype may be linked not only to poorer cardiovascular health in general, but also more specifically to coronary artery calcification and to the process that leads to artery calcification,” says the study's first author, Mio Kobayashi Friska, a doctoral student at the University of Gothenburg's Sahlgrenska Academy, in a university release.

The study accounted for various factors that can influence artery calcification risk, including blood pressure, cholesterol levels, body weight, physical activity, stress, sleep quality, and smoking habits.

“As well as the previously known factors, the individual circadian rhythm also appears to be an important risk factor for artery calcification,” notes study last author Ding Zou, a researcher at Sahlgrenska Academy. “We interpret our results as indicating that circadian rhythm is more significant early in the disease process. It should therefore be taken into account in the preventive treatment of cardiovascular diseases in particular.”

The research had certain limitations, such as excluding individuals who had experienced a heart attack and relying on self-reported chronotypes. The study also noted the average time when half of the night's sleep had passed for each chronotype, with extreme morning types having this midpoint at 2:55 a.m., while for extreme evening types, it was at 4:25 a.m.

SCAPIS — the larger study this research is a part of — is a unique global project focused on cardiac, vascular, and pulmonary disease. It includes extensive health examinations of 30,000 randomly selected Swedes between 50 and 64 years-old, conducted by six universities and university hospitals in collaboration with the Swedish Heart-Lung Foundation.

The study is published in the journal Sleep Medicine.

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