The more your
sleeping schedule changes on non-work days, the more likely there will be
associated health risks, say researchers at the University of Pittsburgh in
Pennsylvania. Researchers from the department of psychology, the department of
psychiatry, and the department of heart and vascular institute published their
study in the Journal of Clinical Endocrinology & Metabolism.
The researchers were
interested in the sleep habits of shift workers, which led to their 2015 study
of non-shift workers (generally 9:00-5:00 workers) who change their sleeping
schedules – for example, people who sleep in on the weekends – their days off
work (which the researchers call social jetlag). Social jetlag is when social
activities, such as going to parties and staying up later, affect the amount of
sleep a person has in a 24-hour period. The researchers refer to social jetlag
as ‘habitual discrepancy between a person’s natural circadian rhythm and actual
sleep imposed by social obligations.’ The study examined the circadian system
of sleep – internal body clocks. In this study, the researchers focused on
circadian dysregulation.
The study involved
447 men and women, aged 30-54, who worked part-time or full-time. Of the 447
participants 53% were female and 83% were white. They all wore devices that
measured movement and tracked their sleeping schedule and habits for 7 days –
work days and non-work days. Almost 85% of participants woke later on their days
off work than during the work week.
The researchers found
that the greater the mismatch (difference) in sleep timing (called chronotype)
between weekdays and weekends the higher the metabolic risk (called
cardiometabolic risk). Sleeping in on weekends was linked to lower HDL (good)
cholesterol, higher triglycerides (fatty acids), higher insulin resistance
(sugar resistance), and higher body mass index (body fat).
In summary, the later
you wake up on the weekends (non-work days) – past your regular waking time
during the work week – the more it influences body fat, cholesterol levels, and
heart disease. If you normally wake up at 7:00 am on the week day, but wake up
at 10:00 am on the weekend, the difference is 3 hours – the bigger the
difference, the more likely there will be health risks, say the researchers. Hence
a misalignment of sleep timing is associated with metabolic risk factors that
might lead to diabetes and atherosclerotic cardiovascular disease.
The researchers are
not yet clear about the long-term effects. They think it is related to internal
body clocks, and suggest that people who don’t vary their sleeping habits have
better health (all other factors being equal) than people who greatly vary
their sleeping habits.
However, the study
did not look at the habits of 20-39 year olds who work – and their weekend
sleeping habits. Also, the study did not differentiate whether participants matched
their internal body clocks to their work schedule (waking up for work) or
whether participants matched their work schedule to their internal body clocks
(waking up naturally and going to work at their own time). So what is the
dysregulation? The researchers say that sleeping in is bad for you if you sleep
in on non-work days. Some would say, sleeping in can be good for you as long as
you do it every day, not just on non-work days.
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