We’ve known for some time that shift work and lack of sleep are both associated with an increased risk of heart disease. We now know a bit more about the physiology that causes this, and whether the increased risk is due to inadequate sleep or to performing shift work. To address those issues, researchers from the University of Chicago recruited 26 healthy people age 20-39 and limited them to 5 hours of sleep a day for 8 days. One group had a set bedtime each night. For the other group, on 4 of those days the study participants went to bed at normal times and on the other days they still were allowed 5 hours sleep, but their bedtimes were delayed by 8.5 hours.
The researchers reported that sleeping for only 5 hours was associated with an increased heart rate during the day whether or not the participants went to bed at a regular time or 8.5 hours later than usual. However, the increased heart rate worsened at night when sleep was delayed by 8.5 hours.
Other effects seen were increased urinary excretion of norephinephrine, a stress hormone that can raise blood pressure and constrict blood vessels, and decreased activity of the vagal nerve, which has a restorative effect on cardiovascular function during deep sleep. This is not good news for people who can’t get enough sleep or don’t sleep regular hours.
In a press release that accompanied publication of the study, lead researcher Daniela Grimaldi, M.D., Ph.D. noted that in humans and all mammals, “Almost all physiological and behavioral processes, in particular the sleep-wake cycle, follow a circadian rhythm that is regulated by an internal clock located in the brain.” When we’re not sleeping and eating at times dictated by this internal clock, the body’s normal rhythms and cardiovascular function may be impaired.
Previous studies have demonstrated other negative effects of short-changing your sleep. The National Sleep Foundation (NSF) has reported that lack of sleep is linked to irritability, impatience, anxiety, and depression and that night workers are more likely than day workers to suffer from heartburn, indigestion and other stomach problems, menstrual irregularities, colds, flu, and weight gain, and are at higher risk of workplace accidents and auto accidents driving back and forth to work.
Some 15 to 30 percent of the population of industrialized countries is engaged in shift work, and there’s not much that most of these people can do about it. The Chicago researchers next want to look into whether or not people who routinely lose sleep – whether or not they’re engaged in shift work – can recover from the negative changes if they can get a few consecutive days of quality sleep. For the time being, however, the researchers recommended that shift workers try to counteract the negative effects of their sleep schedules with a healthy diet and regular exercise.
To add to that, here are some NSF tips that might help shift workers get adequate sleep:
- Wear wraparound dark glasses on the way home from work in the morning to keep sunlight from activating your normal internal “daytime clock.”
- Go to sleep as soon as possible after work and stick to the same schedule daily, even on your days off.
- Avoid caffeine close to bedtime.
- Exercise after you sleep (or if you exercise at work, try and do so at least 3 hours before you plan to go to bed).
Andrew Weil, M.D.
Daniela Grimaldi et al, “Adverse Impact of Sleep Restriction and Circadian Misalignment on Autonomic.” Hypertension, June 6 2016, Doi: 10.1161/HYPERTENSIONAHA.115.06847