A study found that people who are genetically prone to obesity are more likely to become overweight if they don’t stick to normal sleeping patterns. Insufficient sleep and circadian rhythm disturbances both have been associated with adverse cardiovascular outcomes but the cause is unclear. To determine the impact of circadian rhythm disturbances on cardiovascular function in sleep-deprived people, researchers studied 26 healthy people, ages 20 to 39 years. The study participants were restricted to five hours of sleep for eight days with either fixed bedtimes or bedtimes delayed by 8.5 hours on four of the eight days. Researchers found sleep restriction combined with delayed bedtimes when compared to sleep restriction without delayed bedtimes was associated with the following:
- An increased heart rate during the day for both fixed bedtimes and delayed bedtimes groups and even more so at night when sleep restrictions was combined with delayed bedtimes
- Reduced heart rate variability at night
- An increase in 24-hour urinary norepinephrine excretion in the sleep restricted and delayed bedtimes group
- Reduced vagal activity related to heart rate variability during deeper sleep phases (NREM); these deeper sleep phases have a restorative effect on cardiovascular function in normal individual
Norepinephrine is a stress hormone that can constrict blood vessels, raise blood pressure, and expand the windpipe. The vagal nerve’s main effect on the heart is the lowering of heart rate. Researchers said insufficient sleep is particularly common in shift workers, who represent 15 to 30 percent of the working population in industrialized countries. Exposure to consecutive days of sleep loss can impair cardiovascular function, and these negative effects might be enhanced when changes in feeding and/or sleep-wake habits lead to a circadian disruption. Since shift work often can’t be avoided, researchers suggest counteracting measures such as a healthy diet, regular exercise, and more sleep among shift-workers. The same advice applies to everyone else whose sleep is restricted several days in a row.