Sleeplessness impairs crucial mechanisms that keep cardiovascular problems at bay, shows a new study.
Having a good night's sleep, which amounts to an uninterrupted 7 hours of sleep or so per night, is crucial to maintaining good overall health. Poor sleep hygiene disrupts both short- and long-term health, according to evidence from numerous studies.
One aspect of health that a person's quality of sleep can influence is cardiovascular health. For example, research findings from the start of this year showed that sleeping for less than 6 hours per night rather than for 7–8 hours could increase a person's risk of atherosclerosis — a condition in which plaque builds up inside the arteries — by as much as 27%.
Another study from this year explains how good sleep can help keep the arteries supple, thus maintaining good circulation.
Now, research from the University of Colorado Boulder has pinpointed a potential biological mechanism explaining the reverse of the medal — how lack of sleep affects circulation by promoting the buildup of fatty deposits in the arteries (atherogenesis), which can increase a person's risk of experiencing a stroke or heart attack.
The findings, which appear in the journal Experimental Physiology, tie sleeplessness to changes in the blood levels of micro RNA (miRNA), noncoding molecules that help regulate protein expression.
"This study proposes a new potential mechanism through which sleep influences heart health and overall physiology."
Senior author Prof. Christopher DeSouza
How poor sleep promotes vascular problems
In the current study, the researchers collected blood samples from 24 healthy participants aged 44–62 years, who also provided information about their sleeping habits. Of the participants, 12 reported sleeping 7–8.5 hours per night, while the other 12 said that they only slept for 5–6.8 hours per night.
The team found that the participants who slept for less than 7 hours per night had blood levels of three key circulating miRNAs — miR-125A, miR-126, and miR-146a — that were 40–60% lower than those of their peers who slept for 7 or 8 hours. These three miRNAs, the researchers note, suppress the expression of proinflammatory proteins.
Having low levels of these molecules is problematic, because, as Prof. DeSouza explains, "[t]hey are like cellular brakes, so if beneficial microRNAs are lacking, that can have a big impact on the health of the cell."
In this case, insufficient circulating miR-125A, miR-126, and miR-146a could lead to vascular problems, including inflammation, as well as a higher risk of experiencing cardiovascular disease-related events, such as stroke or a heart attack.
Prof. DeSouza and his team had already found another worrying pattern in a previous study, for which they recruited adult men who slept for less than 6 hours each night. The study showed that the participants' endothelial cells — which make up the lining of blood vessels — did not function properly.
As a result, their blood vessels were unable to dilate and contract properly to allow blood to flow efficiently to different organs and parts of the body. This situation, Prof. DeSouza and colleagues have explained, poses another set of risks to cardiovascular health.
7 hours of sleep for cardiovascular health
"Why 7 or 8 hours [of sleep per night] seems to be the magic number [in maintaining health] is unclear," Prof. DeSouza admits.
"However," he continues, "it is plausible that people need at least 7 hours of sleep per night to maintain levels of important physiological regulators, such as microRNAs."
Commenting on the current findings, Prof. DeSouza argues that it may be possible to diagnose cardiovascular disease by performing blood tests. Laboratory technicians could assess a person's levels of circulating miRNAs and look for the presence of the atherogenic signature that the study has identified.
At present, the senior researcher and his team are working to find out whether improving a person's sleep habits can help reestablish healthy levels of important miRNAs in the blood.
In any case, Prof. DeSouza emphasizes that the findings of the recent study corroborate what sleep studies have been suggesting all along — that sleep quality influences unexpected aspects of health.
"Don't underestimate the importance of a good night's sleep," he stresses.