Circadian rhythm confers elevated CV risk among shift workers
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Among individual shift workers, circadian rhythm misalignment was associated with elevated CV risk, according to results presented at the European Society of Cardiology preventive cardiology meeting.
“We all have an internal biological clock, which ranges from morning types (larks), who feel alert and productive in the early morning and sleepy in the evening, to late types (owls), for whom the opposite is true — with most of the population falling in between,” Sara Gamboa Madeira, MD, PhD candidate and medical doctor at the University of Lisbon, Portugal, said in a press release. “Circadian misalignment occurs when there is a mismatch between what your body wants (eg, to fall asleep at 10 p.m.) and what your social obligations impose on you (eg, work until midnight).”
The cross-sectional observational study enrolled 301 blue-collar workers (mean age, 33 years; 56% men) who performed manual picking activity in warehouses in Portugal. The workers always worked in the early morning (6 a.m. to 3 p.m.), late evening (3 p.m. to midnight) or at night (9 p.m. to 6 a.m.). Each participant completed a questionnaire on sociodemographic factors, occupational factors and lifestyle factors. Researchers collected their BP and cholesterol measures.
The Munich Chronotype Questionnaire assessed sleep duration and sleep chronotype and quantified the amount of circadian misalignment. Participants were categorized into groups based on circadian misalignment, with 59.4% in the 2 hours or less group, 33% in the 2 to 4 hours group and 8% in the 4 hours or more group.
In the cohort, 20% of participants were classified as high CV risk and 40% had a short sleep duration of 6 hours or less on workdays. Participants with higher circadian misalignment demonstrated a significant association with increased odds for being at high risk for CVD with a prevalence of 37.5% among those with 4 hours or more compared with a prevalence of 17.3% among those with 2 hours or less (P for trend = .035).
Odds for being in the high CV group increased by 31% with every hour increase in circadian misalignment, the researchers found.
Greater circadian misalignment was also associated with elevated prevalence of hypertension (P for trend = .006) and smoking (P for trend = .043), but not hypercholesterolemia, according to the researchers.
According to Gamboa Madeira, the results support growing evidence that circadian misalignment may aid in explaining the associations between shift work and health outcomes.
“The findings suggest that staff with atypical work schedules may need closer monitoring for heart health,” Gamboa Madeira said in the release. “Longitudinal studies are needed to investigate whether late chronotypes cope better with late/night shifts and earlier chronotypes to early morning schedules, both psychologically and physiologically.”
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Gamboa Madeira S, et al. Moderated abstracts – population science and public health. Presented at: European Society of Cardiology Preventive Cardiology 2021; April 15-17, 2021 (virtual meeting).
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