Working hours that deviate from natural body clock are linked to greater cardiovascular risk, stated a new study.
- Link between social jetlag and high cardiovascular risk established
- Social jetlag is the mismatch between an individual's biological clock and working hours
- Staff with atypical work schedules may need closer monitoring for heart health
At least 20% of European employees work atypical hours or shifts,2 and growing scientific evidence associates these with deleterious cardiovascular outcomes.3 A number of explanations have been proposed, including sleep disruption and unhealthy behaviours. This study focused on the role of circadian misalignment, which is the difference between the "social clock" (e.g. work schedules) and the individual "biological clock".
Dr. Gamboa Madeira explained: "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. Circadian misalignment occurs when there is a mismatch between what your body wants (e.g. to fall asleep at 10pm) and what your social obligations impose on you (e.g. work until midnight)."
The study included 301 blue collar workers, all performing manual picking activity in the distribution warehouses of a retail company in Portugal. Staff always worked either early morning (6am-3pm), late evening (3pm-midnight), or night (9pm-6am) shifts. Participants completed a questionnaire on sociodemographic factors (age, sex, education), occupational factors (work schedule, seniority), and lifestyle factors and had their blood pressure and cholesterol measured.
The Munich ChronoType Questionnaire was used to assess sleep duration, and to estimate each individual's internal biological clock (also called chronotype). It was also used to quantify the amount of circadian misalignment (i.e. the mismatch between an individual's biological clock and working hours) - referred to as social jetlag. Participants were divided into three groups according to hours of social jetlag: 2 hours or less, 2-4 hours, 4 hours or more.
The researchers used the European relative risk SCORE chart which incorporates smoking, blood pressure and cholesterol to calculate relative cardiovascular risk. Relative risk ranges from 1 (non-smoker with healthy blood pressure and cholesterol) to 12 (smoker with very high blood pressure and cholesterol). In this study, a relative risk of 3 or more was considered "high cardiovascular risk". The researchers then investigated the association between social jetlag and high cardiovascular risk.
A higher level of social jetlag was significantly associated with greater odds of being in the high cardiovascular risk group. The odds of being classified high cardiovascular risk increased by 31% for each additional hour of social jetlag, even after adjusting for sociodemographic, occupational, lifestyle, and sleep characteristics and body mass index.
Source-Eurekalert