Here's another reason you should get enough shuteye: new research suggests that insufficient sleep, particularly for shift workers, may increase a person's risk for cardiovascular diseases.

All biological and physiological processes in humans and animals follow a "circadian" rhythm regulated by an internal clock, says Daniela Grimaldi, lead author of the new study.

But when the sleep cycle and feeding cycle are not in sync with the internal clock, Grimaldi says, circadian misalignment occurs.

Grimaldi, who is an assistant professor at Chicago's Northwestern University, says people who experience circadian misalignment may not fully benefit from effects of nighttime sleep to the heart.

A Link To The Cardiovascular System

Past studies have shown that long-term sleep deprivation can contribute to heart disease.

People who experience insufficient sleep the most are shift workers, who represent 15 to 30 percent of the working population.

With that, researchers investigated 26 healthy participants aged 20 to 39 whose sleep were restricted to five hours for eight days. Their bedtimes were either fixed or delayed by 8.5 hours on four of the eight nights.

In the end, Grimaldi and her colleagues discovered that a higher heart rate during daytime was seen for both groups. But the heart rate reached a greater extent when sleep deprivation was combined with late bedtimes.

Additionally, for the sleep-deprived and delayed-bedtime group, there was an increase in the levels of a stress hormone called norepinephrine. This hormone is capable of narrowing blood vessels, raising blood pressure and expanding a person's windpipe, scientists say.

Grimaldi says sleep deprivation and late bedtime are also linked to weakened heart rate variability at night, as well as to reduced vagal activity during deep sleep.

The latter normally has a restorative effect on the function of the heart. Indeed, the main effect of the vagal nerve on the heart is the lowering of the heart rate.

What Shift Workers Should Do

Since night shift work cannot be avoided, Grimaldi says workers are encouraged to follow a healthy diet, exercise regularly and get a decent amount of sleep to protect their heart health.

Details of the study are published in the journal Hypertension. In the meantime, Grimaldi and her team will investigate further whether people who experience sleep loss or circadian misalignment can recover once they get consecutive days of proper sleep.

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