Researchers from the Northwestern University in the US have linked insufficient sleep to heart diseases. Both, insufficient sleep and circadian rhytym disturbances have been associated with adverse cardiovascular outcomes but the cause is unclear.
The body's involuntary processes may malfunction in shift workers and other chronically sleep-deprived people, and may lead to an increased risk of cardiovascular disease, said the scientists. In order to study the impace of circadian rhythm disturbances on cardiovascular function in sleep-deprived people, the researchers studied 26 healthy people aged between 20-39. The participants were restricted to just 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 an increased heart rate during the day for both fixed bedtimes and delayed bedtimes groups.
The same occurred at night. The candidates also experienced 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. "In humans, as in all mammals, almost all physiological and behavioural processes, in particular the sleep-wake cycle, follow a circadian rhythm that is regulated by an internal clock located in the brain," said Daniela Grimaldi from Northwestern University. "When our sleep-wake and feeding cycles are not in tune with the rhythms dictated by our internal clock, circadian misalignment occurs."
"Our results suggest shift workers, who are chronically exposed to circadian misalignment, might not fully benefit from the restorative cardiovascular effects of nighttime sleep following a shift-work rotation," said Grimaldi.
