Sun-Protective Habits Not Linked With Poorer Bone Health

Using sunscreen and following other sun-protective behaviors such as wearing long sleeves or staying in the shade do not decrease bone mineral density overall or increase the risk of osteoporotic fracture, according to a new study that included more than 3,000 men and women.

“We have objective data for the first time, and in a large-scale representative population of the U.S. adults, to indicate sun protection is not associated with negative bone-related outcomes,” said study lead author Mohsen Afarideh, MD, MPH, a postdoctoral research fellow at the autoimmune skin diseases unit at the University of Pennsylvania, Philadelphia.

The study, published online in JAMA Dermatology, goes a step further than previous research by others that has found sunscreen use does not compromise vitamin D synthesis and has little effect on circulating 25-hydroxyvitamin D levels.

In the new study, researchers looked at three sun-protective behaviors – sunscreen use, staying in the shade, wearing long sleeves – and their effects on bone mineral density and the risk of fractures.

While the effects of sun-protective habits on blood levels of vitamin D and BMD scores are important, “what we are more interested to know is if the sun-protective behaviors actually cause or increase the risk of fracture,” Afarideh said in an interview. “The answer to that is a firm ‘No.’ These data are very reassuring and will help clinicians to keep recommending sun protection to the public.”

Study Details

Afarideh and his colleagues from the Mayo Clinic in Rochester, Minn., looked at data from the National Health and Nutrition Examination Survey (NHANES) from 2017 to 2018, obtaining final information on 3,403 men and women, ages 20-59, who completed a dermatology questionnaire The men and women reported on the three sun-protective habits, and noted whether they followed these practices always or most of the time, sometimes, or never or rarely.

The frequency of the three behaviors was not widespread. Frequent staying in the shade was reported by 31.6% of the sample, wearing long sleeves by 11.8%, and sunscreen use by 26.1%.

The researchers also had data on the participants’ bone mineral density (BMD) scores along with dietary information such as milk consumption, vitamin D supplement use, taking steroid drugs, and exercise activity.

“Moderate sunscreen use was linked with a slightly lower lumbar BMD score,” Afarideh said, which was “the only significant association that could be interpreted as concerning.” And this was more likely to be seen in older respondents, he said.

However, otherwise they found the practice of the three behaviors was not associated with lower total or site-specific BMD z scores, nor was it linked with an increased risk of osteoporotic fractures. (The BMD z score compares an individual’s bone density to the average bone density of someone their same age and gender.)

The focus on fracture risk is the more important outcome, Afarideh said. And they found no increased risk overall of osteoporotic fractures in those who practiced sun-protective behaviors.

Moderate to frequent staying in the shade was actually linked with a reduced prevalence of spine fractures in the multivariate model (odds ratio, 0.19; 95% confidence interval, 0.04-0.86, P=.02). The researchers say that may be attributable to these respondents also being careful in other areas of life, such as avoiding falls and not participating in high-risk activities that would increase the chance of fractures. “However, this is just an assumption,” Afarideh said.

Expert Perspectives

Other dermatologists not involved in the new research said the study results provide some “real-world” information that’s valuable for clinicians to share with patients.

“I think this is an important study on multiple levels,” said Henry W. Lim, MD, a former president of the American Academy of Dermatology who is a member of the department of dermatology and senior vice president of academic affairs at Henry Ford Health System, Detroit. “It is a well-done study, involving a large number. It is a real-life situation, asking people their photo protective behaviors and then looking at their bone mineral density.” The bottom line, he said: “Bone health is not affected by photo protection habits in real life.”

The findings are important but not surprising, said Antony R. Young, PhD, emeritus professor of experimental photobiology at St. John’s Institute of Dermatology, King’s College, London, who has researched sunscreens and vitamin D status. “My study showed that correct sunscreen use, albeit with a relatively low SPF of 15, did prevent sunburn in a high UVR [ultraviolet radiation] environment but did allow very good vitamin D synthesis. I think this is because the necessary dose of UVB is very low.”

Michele Green, MD, a New York dermatologist and clinical staff member at Lenox Hill Hospital there, said she often hears concerns about bone health from patients. “Every week, patients ask, ‘Why would I wear sunblock? Don’t I need sun for bone health? Don’t I need it for vitamin D?”‘

Now, she said, “Dermatologists can point to the study and say ‘Don’t worry.’ It clarifies that using sunscreen won’t cause you to have osteoporosis.”

Afarideh, who was a postdoctoral research fellow at the Mayo Clinic, and his coauthors, Megha M. Tollefson, MD, and Julio C. Sartori-Valinotti, of the Mayo Clinic, and Green had no disclosures. Lim and Young consult for the sunscreen industry.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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