Why sleeping less than 7 hours may harm your health

Scientists have found why people who sleep fewer than seven hours every night are at greater risk of stroke and heart attack.

The research, published in the journal Experimental Physiology, shows that sleep deprivation can increase the level of three physiological regulators (microRNAs) in the blood, which influence gene expression and play a key role in maintaining vascular health.

The findings could potentially lead to new, non-invasive tests for sleep deprived patients concerned about their health, according to researchers from University of Colorado Boulder in the US.

"This study proposes a new potential mechanism through which sleep influences heart health and overall physiology," said Christopher DeSouza, a professor at UC Boulder.

MicroRNAs are small molecules that suppress gene expression of certain proteins in cells.

The exact function of circulating microRNAs in the cardiovascular system, and their impact on cardiovascular health is receiving a lot of scientific attention, and drugs are currently in development for a variety of diseases, including cancer, to correct impaired microRNA signatures.

"They are like cellular brakes, so if beneficial microRNAs are lacking that can have a big impact on the health of the cell," said DeSouza.

For the study, which is the first to explore the impact of insufficient sleep on circulating microRNA signatures, researchers took blood samples from 24 healthy men and women, age 44 to 62, who had filled out questionnaires about their sleep habits.

Half slept seven to 8.5 hours nightly while the other half slept 5 to 6.8 hours nightly.

They measured expression of nine microRNAs previously associated with inflammation, immune function or vascular health.

They found that people with insufficient sleep had 40 to 60 percent lower circulating levels of miR-125A, miR-126, and miR-146a than those who slept enough.

"Why 7 or 8 hours seems to be the magic number is unclear," said DeSouza.

"However, it is plausible that people need at least seven hours of sleep per night to maintain levels of important physiological regulators, such as microRNAs," he said.

It is possible that microRNAs in blood could be used as a marker of cardiovascular disease in people with insufficient sleep, enabling doctors to glean important information via a blood test rather than current, more invasive tests, researchers said.