Multiple studies have shown that poor sleep can up your risk of cardiovascular disease, obesity and cancer. But two new studies published last week -- one in the journal Annals of Behavioral Medicine and the other in the journal Scientific Reports -- uncover two more pieces of the puzzle. One reports poor sleep may actually increase the risk for engaging in behaviors that put a person at risk for these chronic diseases to begin with. And the second reports that poor sleep actually changes the way the body gets rid of cholesterol, and likely plays a role in increasing your risk of developing heart disease.
Here's what all this means for you:
People who don't get enough sleep are less likely to engage in heart healthy behaviors
A group of collaborating researchers from the University of Delaware, University of Pennsylvania, Drexel University and the University of Arizona College of Medicine analyzed data from a group of 439,933 adults in the U.K. and found that people who slept six or fewer hours a night were 45 percent more likely to smoke tobacco than those who slept seven to eight hours a night. Those who categorized themselves as night owls were 60 percent more likely to smoke than those who reported being morning people -- and the night owls reported having more sedentary habits and eater fewer fruits and vegetables.
While many people may think of lung cancer and respiratory issues when it comes to the health risks linked to smoking, the chemicals in tobacco smoke actually wreak havoc on our blood cells, too, and that can damage the heart and blood vessels. Over time, this increases the risk of chest pain, heart attack, heart failure, and death.
“We really wanted to understand the relationship between sleep and the major risk factors for cardiovascular disease,” study co-author Freda Patterson, an assistant professor in the University of Delaware's Department of Behavioral Health and Nutrition, told The Huffington Post. “We found that people who did not get adequate sleep -- those who did not get the recommended seven to eight hours -- tended not to engage in heart healthy behaviors.
“Those who tended to be night owls or evening types also tended to have poor heart behaviors.”
“And what was particularly new about these findings was that being a night owl or evening type was associated with poor heart behaviors,” she said.
Night owls were more sedentary and ate fewer fruits and veggies
The 439,933 individuals in Patterson's study answered survey questions about how long they slept, when they slept (i.e. whether they were night owls or early-to-bed and early-to-rise-ers), how long they were physically active each day, and other lifestyle factors.
Participants who categorized themselves as morning types reported watching a little over eight minutes more of TV, spending about 18 minutes fewer on their computers, eating about a sixth of a serving more fruit and about a tenth of a serving more vegetables per day, on average, compared with the night owls.
The link between inadequate sleep and obesity has been well documented in scientific research, Patterson said. But she added that she and her fellow researchers were not aware of other studies that have shown a link between smoking and poor sleep, nor a link between sedentary behavior and poor sleep. The new findings showed a stronger link between sleep and sedentary behavior than between sleep and physical activity, she noted.
“People used to think that if you were physically active you weren’t sedentary,” Patterson explained. “Whereas we are starting to learn that even in people who are physically active and meet the physical activity recommendations, if they’re highly sedentary, then they still have a fair bit of vulnerability to poor health.”
Can improving sleep improve other health behaviors?
These new findings have important implications for public health, Patterson added.
“We think of chronic health risk factors [for chronic diseases like cardiovascular disease, cancer and diabetes] as this core triad -- physical inactivity, tobacco use and poor dietary intake,” she said. “And we know that these risk factors are fairly stubborn to change. It’s very hard to find either community-based or clinical interventions that can help people change these behaviors in the long term.”
Patterson and her colleagues looked at sleep to identify whether there was what she calls a “linchpin behavior” that might affect the other behaviors -- “something central to the co-occurrence of all of these risk behaviors,” she said. And that’s what led them to sleep.
The next step of their work is to look at whether improving sleep can help improve some of the other risk behaviors -- i.e., does improving sleep help more smokers quit? Help people eat healthier? Be more active?
The question, Patterson said, is, “If we improve on sleep, can we improve subsequent health behaviors or not?”
Not getting enough sleep affects your cholesterol
The other new study, conducted in Finland, found that even if a person is able to make health-promoting choices like eating right, being physically active and not smoking, poor sleep may still be hurting their health by raising cholesterol levels.
Though previous studies have connected poor sleep with increased rates of cardiovascular disease and higher overall rates of mortality, these new findings are some of the first data to pinpoint exactly how sleep loss affects cholesterol, a key component of cardiovascular disease risk, said study co-author Vilma Aho, a sleep researcher in the Tarja Porkka-Heiskanen (Sternberg) lab at the University of Helsinki.
"The study established that the genes that participate in the regulation of cholesterol transport are less active in persons suffering from sleep loss than with those getting sufficient sleep," Aho said. "This was found both in a laboratory-induced sleep loss experiment and on the population level."
Sleep loss lowers "good" cholesterol levels
The researchers looked at data from a total of 2,739 individuals, who all answered questions about whether they regularly got sufficient sleep. Each person also gave a blood sample so the researchers could analyze cholesterol levels and other biomarkers, including activity in the genes that help regulate cholesterol.
In people who didn't get enough sleep, the levels of high-density lipoproteins, or “good cholesterol” -- the type that gets rid of excess cholesterol and carries it to the liver -- were on average 10 percent lower compared to the individuals who reported getting enough sleep. Plus, the genes that help regulate cholesterol were found to be less active compared to bodies who got sufficient sleep, Aho said.
“The effect may may be clinically significant in some individuals, especially together with other risk factors.”
The difference in actual levels of "good" cholesterol are relatively small, Aho noted, “but the effect may may be clinically significant in some individuals, especially together with other risk factors.”
The researchers also conducted an experiment for which 14 healthy adults volunteered to restrict their time in bed to four hours a night for five days, while six other adults spent eight hours in bed for five days. The levels of low-density lipoproteins, or “bad” cholesterol, actually decreased by about 10 percent in the individuals who restricted their sleep.
However, that finding doesn't necessarily mean that restricting sleep improves cholesterol levels. Aho said she suspects the decrease might actually have been caused by inflammation in those individuals not getting enough sleep, and noted that the more important takeaway is that cholesterol is influenced by restricted sleep in the first place. The data also showed that once again, the genes involved in cholesterol regulation were less active in individuals who restricted their sleep compared with those who slept longer.
The data from the experimental group of 14 showed that just one week of insufficient sleep changes the body's immune response and metabolism, and for both the large study of individuals and the controlled experiment, the genes that were involved in the body’s normal ridding of bad cholesterol were less active for those who slept less, Aho said.
Taken together, the data suggest sleep loss does affect cholesterol, and over time, sleep loss affects cholesterol metabolism in a negative way.
“In the long run, if the sleep loss becomes chronic, cholesterol metabolism seems to shift to an unfavorable direction, which may increase the risk for developing cardiovascular disease,” she added.