Previous studies have suggested that lack of sleep may increase the risk for cardiovascular disease, and a new study may help explain why; researchers found that sleep deprivation may have a negative impact on cholesterol levels.
Published in the journal Scientific Reports, the study found that sleep loss leads to changes in genes that are responsible for regulating cholesterol levels.
What is more, two population cohorts reveal that people who experience sleep deprivation may have fewer high-density lipoproteins (HDL) - known as 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.
The team reached its findings by conducting experimental and epidemiological analyses.
For the experimental analysis, the researchers enrolled 21 participants who were required to sleep in a laboratory-controlled condition for 5 nights
The sleep duration for 14 of these participants was restricted to just 4 hours a night, while the remaining seven participants enjoyed sufficient sleep each night.
Lack of sleep reduced activity in lipoprotein-regulating genes
Blood samples were taken from all subjects during the study period, which the team analyzed for gene expression and lipoprotein levels.
Compared with participants who had sufficient sleep, the researchers found that those who experienced sleep loss had reduced expression for genes that encode for lipoproteins - that is, there was reduced activity in genes that are responsible for regulating cholesterol levels.
For the epidemiological analysis, the researchers assessed the data of 2,739 participants from one of two Finnish population studies: Dietary, Lifestyle and Genetic determinants of Obesity and Metabolic syndrome (DILGOM) study, and the Cardiovascular Risk in Young Finns Study (YFS).
In the DILGOM study, participants completed questionnaires in which they were asked whether they got enough sleep each night. Subjects who answered "seldom" or "never" were deemed as having "subjective sleep insufficiency."
In the YFS study, subjects were asked how many hours they slept each night and how many hours they need each night to fell well-rested. Their subjective sleep duration was then subtracted from their subjective sleep need in order to determine which participants could be deemed as having sleep deprivation.
Lower circulating HDL with sleep deprivation in population cohorts
On analyzing the blood samples of the participants, once again, the researchers found that subjects who were not getting sufficient sleep had reduced expression of lipoprotein-encoding genes, compared with those who were getting enough sleep.
Additionally, subjects who were experiencing lack of sleep had lower levels of circulating HDL.
The team says the findings from both analyses suggest that just a short period of sleep deprivation may have a big impact on health, and they may explain why people who fail to get enough sleep may be at greater risk for cardiovascular disease.
Study co-author Vilma Aho, from the University of Helsinki Sleep Team, says:
"The experimental study proved that just 1 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."
Medical News Today recently reported on a study that claims to shed light on why we sleep badly during the first night in a new environment.