Sleep is a vital part of human existence. An adequate slumber helps promote a healthy heart, reduces stress, fight depression while also energising the body. When an individual does not get enough sleep at night, the body is unable to heal because the human system produces more protein during sleep, which, in turn, allows the cells to repair any damages.
While various studies have linked chronic sleep disorders to low levels of sleep, to risks of heart disease, obesity and reduced life span, a new research shows that people who get the least deep sleep each night have a higher risk of hypertension.
The study, published in the journal of Hypertension, is one of the first to find that it is the quality of your sleep at night - and not how many hours it lasts - that can affect your risk for high blood pressure.
The aim of the study, carried out by researchers at Harvard Medical School, was to look specifically at the slow-wave stages of sleep, which are said to be made up of about 90 minutes to two hours of a normal night sleep. This time frame also represents the deepest hours of sleep.
While trying to discover the effect of deep sleep on health, the scientists examined 784 healthy men who were part of an ongoing sleep study and did not have signs of high blood pressure at the start of the research. During the three-and- a-half year study, the blood pressure of the men was checked at various times while their levels of slow-wave sleep were monitored at home by a machine.
After examining them for a number of variables, the researchers found that the men who spent the least time in slow-wave or deep sleep were the most likely to develop high blood pressure. Although a night of normal sleep should consist of about 25 per cent slow-wave sleep, the researchers say that the men in the study who had the highest risk for hypertension managed to enjoy deep sleep for no more than 4 per cent of their total sleep each night. The researchers found that the men with the least deep sleep were more likely to have sleep apnea and tended to sleep less over all.
Explaining the outcome of the research further, an author of the study and a professor of sleep medicine at Harvard Medical School, Dr Susan Redline, says that although the study examined only men, she believes the results will also apply to women who fail to get enough deep sleep.
She says, “During slow-wave sleep, the brain’s electrical activity slows down, as do a person’s heart rate, adrenaline levels and blood pressure. The average person’s blood pressure falls about 10 millimeters of mercury during slumber, a dip that largely occurs when deep sleep sets in. This nightly fall in blood pressure is a good thing. It is also known that the areas of the brain that regulate sleep patterns have a lot of crosstalk with areas of the brain that release hormones and other mediators that influence blood pressure. When those areas of the brain are not entering slow-wave sleep, it may interfere with various brain signals that influence blood pressure.”
The researchers also reveal that an adequate amount of slow-wave sleep can be influenced by a number of factors. According to them, any condition like loud snoring, sleep apnea or restless legs syndrome that disrupts your sleep at night can shorten your slow-wave sleep, as can medications. Even your age can have an effect especially since deep sleep declines as one gets older.
Suggesting ways to encourage a deep night sleep, the researchers say that various studies show that being more physically and cognitively active can increase the amount of time you spend in deep sleep at night.
“Some of that research comes from animals,” Dr. Redline notes. “If you give animals more tasks to do during the day they have more slow-wave sleep at night.”
The only way to know precisely the amount of time you drift into deep sleep each night, they say, is through an overnight sleep study. But the key to finding this out, according to Redline, is to assess whether you feel rested in the morning and alert and ready to go after seven to eight hours of sleep.
“If you’re feeling tired and not refreshed after a full night’s sleep, that is a good indication that you need to talk to your doctor, and then your doctor would decide whether you need to see a sleep specialist,” she says.
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