New research suggests postmenopausal women who sleep less than 5 hours a night have a higher risk of osteoporosis.
The number one risk factor for low bone mineral density and osteoporosis is something that we can’t avoid: getting older. Other uncontrollable osteoporosis risk factors include gender, bone structure, and race. But there are also factors in our control that we can act on to help keep our bones stronger for longer, which include getting the recommended amount of physical activity, following a healthy diet, and not smoking.
Now new research published November 6, 2019, in the Journal of Bone and Mineral Research has suggested that an additional way to keep bones strong is to get enough sleep on a nightly basis.
Investigators found that women who slept five or fewer hours a night had a significantly lower bone mass density (BMD) and a greater risk for osteoporosis compared with women who had a full night’s sleep of at least seven hours. Stronger bones mean fewer fractures, which is one or the most prevalent heath issues that older women face. According to the National Osteoporosis Foundation (NOF), one-half of all women over age 50 will break a bone because of osteoporosis; a woman’s risk of breaking a hip is equal to her combined risk of breast, uterine, and ovarian cancer.
The key takeaway is that the research shows that sleep was found to play an important role in yet another aspect of our health: bone health, says Heather M. Ochs-Balcom, PhD, associate professor in epidemiology and environmental health at the University of Buffalo in New York and coauthor of the study. (Plenty of other research has established that sufficient sleep promotes mental, heart, metabolic, and immune health.) “Hopefully people will use this evidence as another reason to practice good sleep hygiene,” she adds.
Does Sleep Help Bones Stay Stronger?
To find out if the amount or quality of sleep impacts bone mineral density and osteoporosis risk, investigators looked at 11,084 postmenopausal women with an average age of 63.
Women are at an increased risk of poor bone health after menopause because when women go through menopause their levels of estrogen, a hormone that protects bones, drop significantly. As a result, women can lose up to 20 percent of their bone density in the five to seven years after menopause, according to the NOF. This can put women at increased risk for developing osteoporosis and bone fracture.
The women in the new study were a subgroup of the Women’s Health Initiative (WHI) study who had undergone a complete dual-energy X-ray absorptiometry scan, the gold standard for determining bone mineral density.
Bone mineral density of the total hip, femoral neck, spine, and total body were all measured. Women were classified according to their bone mass and whether or not their scores indicated they had osteoporosis.
Sleep was assessed through questionnaires that participants completed about how many hours they slept on a typical night in the preceding four weeks. The women were also asked about how often they woke up during the night, if they had trouble falling asleep, and if they woke up earlier than they planned to. Sleep quality was rated on a scale from 0 to 20, with higher numbers indicating greater insomnia.
Seven hours of sleep per night was used as the reference group because this is the minimum recommended amount of sleep for adults per night, according to an article published November 2015 in the Journal of Clinical Sleep Medicine.
After adjusting for factors such as race, education, smoking, alcohol use, physical activity, body mass index (BMI), and sleep medication use, the researchers found:
- Women who slept five hours or less a night had a 22 percent higher risk of having low bone mineral density and a 63 percent higher risk of having osteoporosis of the hip compared with the women who slept seven hours a night.
- The women who slept less than five hours a night had a 28 percent higher risk of osteoporosis of the spine, and a 94 percent increased risk of osteoporosis of the whole body compared with those who slept seven hours per night.
- Sleeping longer than seven hours didn’t add any additional benefit in terms of bone mineral density or osteoporosis risk reduction.
This study is a follow-up to research published in March 2019 in the Journal of Bone and Mineral Research, according to Dr. Ochs-Balcom.
“In that study we looked at sleep and found that women who had short sleep were more likely to have a fracture,” she says. “We wanted to know more about what could be behind that association. Was it that the women who slept less were walking around more or was it because they actually had lower bone mineral density?”
By analyzing the bone density scans, this new data tells a little bit more of the story, she adds. Though there are still questions about the relationship between nightly sleep and bone health.
Additional Research With More Objective Measures of Sleep Needed to Corroborate Results
These results do suggest an association between getting five hours or less of sleep and having lower bone mineral density, but they do not prove that shortened sleep is actually causing the bones to be weaker, according to Sara E. Benjamin, MD, clinical associate at the John Hopkins Center for Sleep in Baltimore.
“I would think that changes in bone density take many years to develop, so to me a person’s self-reported sleep in the past four weeks may not be a good measure of how the person has slept in the past years. In the past month they may have had a medical issue or stressor that would have led to less than their normal amounts of sleep,” says Dr. Benjamin.
Another potential limitation of the study is that people’s self-report of sleep duration may not always be reliable, according to Benjamin. A recent bad night of sleep can make a person think that overall they sleep poorly, causing people to underestimate the amount of time they sleep, she says.
“If one wants to test the strength of this association, more objective measures of sleep duration should be considered, including using activity or brain wave monitors to look at how much time people sleep,” Benjamin says. “The results of this kind of monitoring could be compared with the results of sleep questionnaires to see how much they truly match,” she says.
What Happens During Sleep That Protects Bones? More Research Is Needed to Find Out
Although the study wasn’t designed to look at why a lack of sleep might negatively impact BMD and increase the risk for osteoporosis, the authors have a few thoughts about why the association might exist.
“We know that bone remodeling takes place when we sleep — that would be the simplest explanation,” says Ochs-Balcom. If you’re sleeping less, the process that bones need to go through to remain healthy isn’t able to happen in the proper way, she explains. But we’d need more studies that look at additional factors to prove that’s happening, she adds.
It’s important for your overall health and long-term wellness to take care of your bones, says Ochs-Balcom. “These findings suggest that sleep is important, but that’s just one component. Women also need to get the recommended amount of physical activity and eat a healthy diet to maintain bone health,” she says.
Becky Upham
MAY