What About Sleep Causes High Blood Pressure?
Funny things happen with media stories. Complicated science suddenly becomes simple, clear and distinct – with implications very different to what the research reveals.
Such is the case with a recent article on hypertension. According to the report in BBC News, “Bad Sleep Ups Blood Pressure Risk.” What did the article really show? That in elderly men (average age 75) the quarter of them with the lowest deep sleep percentage did indeed go on to hypertension within three years – but that how much their sleep was fragmented, how long they slept, and how many apneas they had did not affect that outcome.
The Study
The research was performed through the San Diego VA and Pacific Medical Center in San Francisco, with Dr. Susan Redline, a long working and well established sleep epidemiologist, coordinating parts of the study. It looked at 784 men “in the community” – which means many were not completely health, though all of whom were over 65. Their health parameters were followed for three years.
The only independent impact on blood pressure appeared in those with the lowest amount of the stage of sleep known as deep sleep – which is also called slow wave sleep, or in youth, quiet sleep. Normally deep sleep declines with age – from adolescence on. It particularly goes down through middle age, especially in men. Women keep their deep sleep proportion of sleep for much longer times than males, but it still declines in women, too.
What Happens in Deep Sleep?
Plenty. In deep sleep the human brain looks as close to coma as it normally gets. Long, slow electrical waves flow across the cortex. Deep sleep is so separate from normal existence that it’s the period in which most people experience sleepwalking, performing bizarre acts they do not remember later on. That includes murder, like the famous Parks case in Ontario, who tried to kill his well-liked parents-in-law while in deep sleep.
Redline points out that blood pressure normally goes down in deep sleep. So those with more deep sleep should show average lower blood pressure – at least at night.
However, it’s been known a long time that for those with hypertension, their blood pressure does not “dip” during sleep. Something abnormal is keeping it high.
One factor in producing that hypertensive change may be the lack of deep sleep.
And deep sleep is critical for many other functions. You need it for memory and improved cognition. People with less deep sleep don’t think as well.
And during deep sleep you produce more growth hormone. Growth hormone literally makes things grow – reshaping your body and brain. Much of growth hormone’s effects are mediated by insulin growth factor-1, which changes weight, muscle distribution, and energy metabolism throughout the body.
Bottom line – you want to keep your deep sleep long and deep.
What Does This Study Really Say?
For these elderly men, there is a correlation between a lot less deep sleep and hypertension. However, many other sleep factors affect hypertension. Sleeping less than 6 hours predisposes people to high blood pressure. Having sleep apnea, stopped breathing episodes, is strongly associated with hypertension. People who complain about poor sleep experience more hypertension (in this sense the BBC’s headline was correct.)
This study showed that even when you control all these factors, less deep sleep still appears to have a hypertensive effect – in elderly males.
If Deep Sleep Is Important, What Can I Do to Increase It?
Young people have lots of deep sleep, but making the aging clock turn backwards is not so simple.
Instead, some easy to change factors do improve deep sleep percentage:
- Good sleep hygiene – going to bed and getting up at the same times improves sleep in general – particularly sleep continuity. Since you need to have lots of continual sleep to get into deeper phases of sleep – particularly deep sleep and REM – having a nice, comfortable, cool, dark place to sleep following your regular sleep ritual (flossing, brushing, putting out tomorrow’s clothes, reading) is a pretty cheap way of getting better sleep and more deep sleep.
- Getting fit. People who are fitter have more deep sleep.
- Hot baths. Passive body heating – getting your body warm enough by heating the spinal cord to sweat – can, as described by Janet Mullington, increase overall sleep continuity and deep sleep percentage.
So how can you put these factors together? Take a stroll or walk with your family after the evening meal. For a half hour or hour before sleep, turn down the lights, read, joke, or listen to music. Whenever you feel a bit uptight, take a hot bath – hot enough to sweat.
Doing so may lower your blood pressure and allow you to produce you more growth hormone. You should feel more rested each morning. And with rest comes regeneration – part of deep sleep’s role in remaking and recreating your body.
Which is its own reward.
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