It’s the middle of the night and you’re staring at the ceiling.
Slowly, so slowly, the minutes tick by. It feels like forever before you fall back asleep – just in time for your alarm clock to go off.
If this sounds familiar, you’re not alone. Nearly one-quarter of Canadians reported experiencing symptoms of insomnia and about one-third reported sleeping for less than the recommended seven or eight hours, according to a Statistics Canada report from December 2018.
This can have profound consequences for your health that go beyond simply feeling tired, cranky and slow the next morning.
A growing body of research is pointing to the long-term consequences of too little or poor-quality sleep, suggesting it’s connected to poor cardiovascular and mental health, metabolic disorders and possibly even conditions like dementia.
Sleep is important to health, said Charles Morin, the Canada research chair in sleep disorders at Laval University and president of the World Sleep Society. “It’s one of the three pillars for sustainable health.”
“Sleep is just as important as good nutrition or exercising.”
While we’re asleep, our bodies are still busy, taking care of things that it doesn’t do when we’re awake. One example Morin gives is hormone production.
“At night, we produce a number of hormones including leptins. Leptins are an appetite-controlling hormone so if we only sleep four or five hours a night, we produce less of that hormone and therefore we’re at greater risk to become overweight and eat more,” he said.
Similarly, getting too little or too much sleep is associated with changes in how our bodies react to glucose, and a higher risk of developing Type 2 diabetes.
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When we’re sleeping, our blood pressure also decreases relative to when we’re awake. Sleep disturbances, like insomnia or sleep apnea – a breathing disorder – can interrupt this rhythm. “It’s like the heart is working overtime and it may predispose these individuals to higher risk for hypertension,” Morin said.
A 2015 statement from the American Heart Association found that short sleep duration was associated with a higher risk of hypertension and of coronary heart disease, and recommended public-health campaigns to increase awareness of the importance of a good night’s sleep.
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Sleep also affects your mental health. In a 2016 meta-analysis, insomnia was associated with a higher risk of depression, though the connection can go both ways – people with depression often have trouble sleeping, and trouble sleeping might lead to a higher risk of depression. Treating sleep disorders alongside depression can lead to a better outcome for both conditions, Morin said.
Sleep might even affect how well your brain works. Right now, an Ontario study is even examining a possible association between sleep and the brain’s health, alongside other health issues. The Ontario Sleep Health Study, which has examined about 2,800 people so far, is hoping to publish some results later this year, focusing on signs of dementia.
“What we’re interested in doing is taking a look at folks in mid-life and try and get a feeling for whether we are starting to see early changes in MRIs and cognitive function that may lead to dementia in a working-age population,” said the study’s principal investigator, Dr. Andrew Lim of Toronto’s Sunnybrook Hospital.
During sleep, he said, the brain flushes out toxins. “There’s a mechanism whereby waste products that are produced by neurons and other cells in the brain build up during the day and then when you sleep, they are literally flushed out of the brain.”
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In a 2017 review, researchers found that several studies point to a link between sleep deprivation and more amyloid-beta protein accumulating in the brain – thought to be a key factor in the development of Alzheimer’s disease.
Although clinical trials haven’t yet proven that sleep deprivation causes dementia or Alzheimer’s, Lim said, “I think the data is building that this might be one potential consequence of sleep disruption.”
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The sleeping brain may also play an important role in learning and memory, he said. “When you’re awake, as you learn new things and as you remember new things and encounter new experiences, you form new connections between neurons in your brain, called synapses.”
“What happens is if you kept on building up new synapses, over time, your brain would simply become overloaded with new synapses, many of which are not necessarily important.” During sleep, he said, the brain reinforces synapses that are most important for learning and pares back the less important ones, leaving room for new connections to be formed the next day. “This process is critically dependent on sleep, making sleep an important mediator of learning.”
While trials showing this have so far mostly been done in mice – it’s much harder to examine synapses when you can’t do an autopsy of the brain – Lim thinks it’s clear that poor sleep makes it harder for you to learn. If you treat someone’s sleep apnea, for example, “you can see immediate obvious changes in cognitive performance.”
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The upshot of all this? We need to make sleep a priority, Morin says. “There are very significant costs associated with chronic insomnia in the work environment and in one’s own personal life in terms of fatigue, decreased energy and even mood disturbances.”
If your poor sleep lasts for more than a few nights a week for a few weeks, and it’s having an impact on your daytime functioning, you should contact a health-care provider, he said.
“People need to make a priority of their sleep,” he said.
“We need to prepare ourselves for a good night’s sleep, just as we do when we travel. We prepare our journey ahead of time. We need to do the same when we sleep.”
Although the amount of sleep needed varies from person to person, experts generally recommend about 7.5 to eight hours of sleep every night, with some rare people needing as little as six or as many as nine hours. If you feel tired after a night’s sleep, try sleeping longer until you find what’s right for you, the Canadian Sleep Society suggests.
If you have persistent trouble sleeping, or no amount of sleep makes you feel well-rested, contact a medical professional, since sleep is important for your overall health.
“I think we take it for granted until we have problems with it,” Morin said.
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