Do ‘night owls’ face higher heart health risks?

Artery calcification is almost twice as common in people who stay up late, according to a study from the University of Gothenburg, Sweden. The scientists found that circadian function is particularly important during the early stages of cardiovascular disease.

The paper makes for worrying reading for ‘night owls’ compared to ‘early birds’ who are bright and breezy in the morning. Atherosclerosis involves fatty deposits accumulating on the inside of the arteries, making it harder for blood to pass through. The disease develops over a very long period of time and is not noticed until it leads to blood clots causing angina, heart attack, or stroke.

Previous research has shown that people with late-night habits have an increased risk of cardiovascular disease, but this is the first study to show how circadian rhythms specifically affect calcification of the arteries.

The study, published in the journal Sleep Medicine, involved 771 men and women aged between 50 and 64, all of whom are part of the larger population study SCAPIS. The degree of artery calcification in the heart’s coronary arteries was examined using computer tomography. Participants themselves indicated their so-called chronotype on a five-point scale: extreme morning type, moderate morning type, intermediate type, moderate evening type, or extreme evening type.

Of the 771 participants, 144 identified as extreme morning types, and 128 as extreme evening types. Among the group who were most alert in the morning, 22.2% had pronounced artery calcification – the lowest proportion of all five chronotypes. The extreme evening type group had the highest prevalence of severe coronary artery calcification, at 40.6%.

Mio Kobayashi Frisk, a doctoral student at Sahlgrenska Academy, University of Gothenburg, said the results indicate that extreme evening chronotype may be linked not only to poorer cardiovascular health in general, but also more specifically to calcification in the coronary arteries.

The statistical analysis considered a range of other factors that can affect the risk of atherosclerosis, including blood pressure, blood lipids, weight, physical activity, stress level, sleep, and smoking.

Ding Zou, a researcher at the University of Gothenburg said the results show that circadian rhythms are more significant early in the disease process. ‘It should therefore particularly be considered in the preventive treatment of cardiovascular diseases,’ says Ding Zou.