Hardened arteries are almost twice as common in night owls as in early birds, a new study shows.
About two in five people (40%) who stay up very late had severely hardened arteries, compared with 22% of people who wake early, according to the report in the journal Sleep Medicine.
“The individual circadian rhythm also appears to be an important risk factor for atherosclerosis,” said senior study author Ding Zou, a researcher at the University of Gothenburg’s Sahlgrenska Academy in Sweden.
Further, the findings indicate that “circadian rhythms are more significant early in the disease process,” Zou added in a university news release. “It should therefore particularly be considered in the preventive treatment of cardiovascular disease.”
Previous research has shown that people with late-night habits have an increased risk of heart disease, but this is the first study to show that sleep rhythms are related to a specific heart health risk factor, the researchers said.
For the study, the team analyzed data from nearly 800 men and women between the ages of 50 and 64 who were participating in a large-scale imaging study of diseases of the heart, lungs and blood vessels.
Participants were sorted into one of five groups based on their “chronotype” — the natural inclination to sleep at a certain time.
These groups were typed as extreme morning, moderate morning, intermediate, moderate evening or extreme evening.
CT scans showed that night owls had nearly twice as much atherosclerosis as early birds, even after accounting for other heart health factors like blood pressure, cholesterol, weight, exercise, stress and smoking.
Atherosclerosis involves fatty deposits accumulating on the inside of the arteries, clogging blood flow.
“Our 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 calcification and atherosclerosis,” said lead researcher Mio Kobayashi Frisk, a doctoral student at the University of Gothenburg.