Sleep affects every aspect of your health, from your mood to memory to exercise habits.
It’s widely known that sleep deprivation is harmful in myriad ways — but now, new research shows that over-sleeping is damaging, too.
Regularly sleeping for more than nine hours at a time and taking long midday naps has been shown to increase a person’s risk of stroke, according to a study published in Neurology on Wednesday.
Researchers analyzed the sleep patterns of 31,750 people in China over six years. The average age was 62, and the study controlled for other stroke risk factors, like smoking, drinking, and history of stroke and other heart issues.
Respondents who slept more than nine hours per night had a 23 per cent higher risk of stroke. Those who frequently had a midday nap longer than 90 minutes experienced a 25 per cent increase in risk.
For people who slept for longer than nine hours and had a midday nap longer than 90 minutes, the risk of stroke jumped to a whopping 85 per cent.
The reason behind the association is unclear to researchers, but they did note that increased sleep duration was also related to increased inflammation and weight, among other factors known to negatively affect the heart.
Sleep has a “bi-modal distribution,” said Sheila Garland, a registered clinical psychologist and an assistant professor at Memorial University in Newfoundland and Labrador. This means there are two modes of sleeping: too little and too much.
“It’s not good to sleep too little, but it’s also not good to sleep too much,” she said.
A vicious cycle
The trouble for researchers is excess sleep can be both a cause and a symptom: It can cause other health problems to occur, but it can also be a symptom of other underlying health conditions.
It’s a vicious cycle, said Garland.
“It’s tricky because you don’t know whether it’s compromised by health conditions that existed prior … making it more likely that you’re going to increase your sleep duration, or that the increase in duration itself makes you more likely to have health conditions,” she said.
Sleep disorders like hypersomnia and sleep apnea can affect the length of a person’s sleep cycle. Mood disorders are another common culprit.
“Often, people with mood disorders like depression will see an increase in the amount of time that they sleep,” Garland said. “One of the key characteristics of depression is too little or excessive sleep. That needs to be considered.”
In determining why someone is sleeping too much (or too little), both physical and psychological conditions should be considered.
Charles Morin, behavioural sleep medicine researcher and professor at the University of Laval in Quebec City, has seen this scenario many times before.
“We long thought that insomnia was just a symptom of depression, and if we treated the depression, it would take care of the insomnia problem automatically,” he said. “That isn’t the case.”
People without depression can develop insomnia, but the sleep condition can greatly increase their risk of developing depression later on, said Morin.
“If someone now is struggling with depression and insomnia, we recommend that they receive treatment for both conditions,” he said.
The circadian rhythm
Sleep is one of the three “critical pillars of health,” along with good nutrition and exercise, said Morin.
What constitutes a good night’s sleep is different for everyone, but for the most part, adults should get seven to eight hours of sleep a night, he said.
It’s totally normal to need slightly less (five to six hours) or slightly more (nine hours), but this isn’t the average experience. If you sleep for 10 hours at night and still feel tired the next day, Morin suggests you see a doctor.
Garland says good sleep has three components: “enough sleep duration,” “good sleep quality” and it’s “appropriately timed.”
This means you’re listening to and following your circadian rhythm — a function of the brain that controls the responses when your body does certain things with hormones.
“It tells us when to be awake and when to be asleep, and it influences the production of hormones,” said Garland. “Every cell has a clock that tells it to turn on and turn off.”
“Every living thing has the machinery in all of its cells, including our human brains, to recognize the rising and the setting of the sun,” Richard Horner, a professor of physiology at the University of Toronto, previously told Global News.
He said our bodies take cues from the light around us to figure out when it’s day or night, and that influences when we want to sleep or wake up. Bright lights in the morning can “reset” your personal circadian rhythm so you can be certain it’s on the right schedule.
Some people prefer to wake up early and go to sleep early, while others like to stay up late and rise later, too. These concepts aren’t just in our heads, said Garland.
“They’re genetically determined and, if you try to work against your genetics, it can be very hard on your body,” she said. That’s why people who work shifts or overnight often have more health problems than those who don’t.
“They’re basically working against their circadian rhythm,” said Garland. “They’re being awake when their body really wants them to be asleep.”
Sleeping the right amount
If you’re worried that you might be over-sleeping, Garland recommends trying to cut back over a two-week period.
“See if it actually makes you feel better,” she said. “But it needs to be consistent. The most important thing would be for people to get a wake-up time that’s consistent.”
If you don’t feel any different after the change, or if it was nearly impossible to alter your sleep pattern, Garland recommends seeing a doctor.
— With files from Josh Elliot