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Increased risk of subclinical atherosclerosis among evening chronotypes

Dr. Mio Kobayashi Frisk

Dr. Mio Kobayashi Frisk

Resident physician in psychiatry at the Sahlgrenska University Hospital and PhD student at the Center for Sleep and Vigilance Disorders, University of Gothenburg. Follow on LinkedIn.

Dr. Mio Kobayashi Frisk obtained her Bachelor of Science degree with Honors in Biology from Stanford University, where her research focused on sleep, circadian rhythms, memory, and Down Syndrome. She later studied the effects of light on sleep and circadian rhythms at the University of Strasbourg and the CNRS, and obtained her medical degree from the University of Gothenburg. She is currently a resident physician in psychiatry at the Sahlgrenska University Hospital and a PhD student at the Center for Sleep and Vigilance Disorders, University of Gothenburg, where her research focus is on sleep, circadian rhythms, and cardiovascular health.

Study Overview and Objectives

Evening chronotype has previously been associated with unhealthy lifestyle, cardiovascular morbidity, mortality, and cardiovascular risk as determined by the Systematic Coronary Risk Estimation 2 (SCORE2). However, there is no clear understanding of the underlying mechanisms.

Mio and her coauthors examined the relationship between chronotype and atherosclerosis in their latest study, “Eveningness is associated with coronary artery calcification in a middle-aged Swedish population”. Calcified plaque in the coronary arteries was visualized in 771 participants of the Swedish CArdioPulmonary bioImage Study (SCAPIS) pilot by computed tomography and quantified based on volume and density to produce a coronary artery calcification (CAC) score (CACS). CACS is a widely used biomarker of atherosclerotic burden, and a high score is associated with cardiovascular disease and death. Chronotype was determined by questionnaire in which participants classified themselves as either extreme morning, moderate morning, intermediate, moderate evening, or extreme evening type. 23 other anthropometic, socioeconomic, comorbidity, and lifestyle factors were determined by accelerometry, blood samples, questionnaire, and a clinical visit.

The Findings

Significant CAC (defined as a CACS > 10), was nearly twice as common in extreme evening types (40.6%) compared to extreme morning types (22.2%). Analysis which accounted for other potentially related factors such as SCORE2 risk, body mass index, physical activity level, and diabetes indicated that extreme evening types still had 90% greater odds of significant CAC compared to extreme morning types.

Subsequently, the participants were stratified into five subgroups according to risk group as determined by SCORE2 (low: <5%; moderate: 5 to <10%; high: ≥10%) and chronotype (extreme evening type vs non-extreme evening chronotype). Compared to non-extreme evening chronotypes with a low SCORE2 risk, extreme evening chronotypes with a high SCORE2 risk had over 15 times greater odds of having significant CAC, independent of other potentially relevant factors. Moreover, within each SCORE2 risk group, the prevalence of significant CAC was markedly increased among extreme evening types in the low and medium risk groups, but not in the high risk group.

Conclusions

These results indicate that chronotype is associated with not only health, lifestyle, and mortality, but even with atherosclerosis. This suggests that the circadian system may have influence on the biological mechanisms which lead to cardiovascular disease, as extreme evening chronotype may represent a form of dysregulation in the circadian system, similar to jet-lag and shift work. In a clinical setting, the results suggest that chronotype and circadian health may be an important factor to consider when assessing cardiovascular risk, especially at the early stages in primary prevention.

Article and infographic based on:
Kobayashi Frisk et al. (2023). Eveningness is associated with coronary artery calcification in a middle-aged Swedish population. Sleep Medicine.

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