It seems that every week science is giving us another reason to stay in bed. Now University of Helsinki researchers have found that sleep loss also influences cholesterol metabolism.

A new study conducted at the University of Helsinki examined the impact of cumulative sleep deprivation on cholesterol metabolism in terms of both gene expression and blood lipoprotein levels. They discovered that lack of sleep has a big impact on our cholesterol levels. Specifically, people who experience sleep deprivation may have fewer high-density lipoproteins (HDL) - the "good" cholesterol - than those who have sufficient sleep. HDL cholesterol is responsible for removing low-density lipoproteins (LDL) - the "bad" cholesterol - from the arteries.

LDL cholesterol contributes to atherosclerosis - a build-up of plaque in the arteries that can increase the risk for heart attack and stroke - so a robust HDL cholesterol level is important for protecting heart health.

"In this case, we examined what changes sleep loss caused to the functions of the body and which of these changes could be partially responsible for the elevated risk for illness," explains Vilma Aho, researcher from the Sleep Team Helsinki research group.

The study established that the genes which participate in the regulation of cholesterol transport are less active in persons suffering from sleep loss than with those getting sufficient sleep. This was found both in the laboratory-induced sleep loss experiment and on the population level.

Together with other risk factors, these results help explain the higher risk of cardiovascular disease observed in sleep-deprived people and help understand the mechanisms through which lack of sleep increases this risk.

"It is particularly interesting that these factors contributing to the onset of atherosclerosis, that is to say, inflammatory reactions and changes to cholesterol metabolism, were found both in the experimental study and in the epidemiological data," Aho says.

The results highlight the health impact of good sleep. The researchers emphasize that health education should focus on the significance of good, sufficient sleep in preventing common diseases, in addition to healthy food and exercise. Even a small reduction in illnesses, or even postponing the onset of an illness, would result in significant cost savings for society at large.

"The experimental study proved that just one week of insufficient sleep begins to change the body's immune response and metabolism. Our next goal is to determine how minor the sleep deficiency can be while still causing such changes," Aho states.