Sun-Protective Measures Not Associated with BMD, Osteoporosis Risks

Mohsen Afarideh, MD, MPH

A new cross-sectionally study suggested that the use of sun-protective behaviors typically adopted among the US adult population was not associated with decreased bone mineral density (BMD) or increased risk of osteoporotic fracture.

The investigators, led by Mohsen Afarideh, MD, MPH, Department of Dermatology, University of Pennsylvania, considered these to be “reassuring findings” that added to the growing body of evidence regarding sun protection with no considerable negative associations with bone health.

Prior to the study, little was known regarding the potential effects of protective measures such as sunscreen on potential complications of vitamin D deficiency.

As such, Afarideh and colleagues analyzed data from the National Health and Nutritional Examination Survey (NHANES) to determine correlates of sun protection while investigating any potential association of multimodal sun-protective behaviors with BMD and more among US adults.

The Methods

Over the course of the study, Afarideh and investigators analyzed data from adults who participated in NHANES from 2017 to 2018. The data were analyzed between September and November 2020.

Data from 5569 individuals were analyzed, all of whom were 20 years and older. Of the total number of individuals, 3403 completed the dermatology questionnaire that was featured in the study. I

The final subsamples selected to analyze the associations of sun protective behaviors with BMD and osteoporotic bone fractures contained data from 2585 and 917 individuals, respectively.

Investigators defined sun sensitivity by the amount of sun exposure for 30 minutes without any sun protection after several months of not going out in the sun.

Additionally, survey respondents assigned to 1 of 3 categories: severely sun sensitive, mildly sun sensitive, and not sun sensitive.

The BMD was evaluated with a dual x-ray absorptiometry technique while participants visited mobile examination centers, and weekly metabolic equivalent task (MET)-minute aggregated scores were calculated to measure the amount of energy expenditure patients showed during physical activity.

Finally, covariates such as total vitamin D supplement intake was determined based on dietary records of participants in the 30 days leading up to the study, and milk consumption and prednisone or cortisone was defined based on standard responses (“yes”, “no”, etc.)

The Findings

Investigators reported on data regarding the prevalence of 3 sun-protection components featured in the study.

Of the total number of individuals featured in the study, 31.6% stayed in shaded areas, 11.8% wore long-sleeve clothing, and 26.1% used sunscreen.

Afradideh and colleagues noted that an increasing number of sun-protective behaviors were likely adopted by older and female participants.

Additional factors included participants who originated from Mexican American or non-Hispanic Asian descent, were educated with advanced degrees at college level or above, born abroad, nonsmokers, engage in less physical activity, experience sunburns, and have mild-to-severe sun sensitivity, among others.

Each individual sun-protective behavior was associated with statistically significant decreases in several site-specific and total BMD z scores in baseline models. However, these associations largely faded following the multivariate adjustments for potential confounders.

Afradideh and investigators found that frequency of sunburns was significantly elevated among individuals with severe sun sensitivity (72.9% [95% CI, 65.5%-79.2%]) and mild(52.3% [95% CI,48.1%-56.4%]) compared with individuals who reported no sun sensitivity (23.3% [95% CI,19.5%-27.5%];P< .001).

In multivariate models featured in the study, the use of individual sun-protective behaviors was not associated with diminished site-specific and total BMD z scores. Additionally, moderate to frequent staying in the shade was associated with reduced prevalence of spine fractures in the multivariate model (odds ratio, 0.19 [95% CI, 0.04-0.86],P= 0.02).

Overall, the results of the study demonstrated that routine practice of sun protection was not associated with increased bone-related health complications such as decreased BMD or increased osteoporotic fractures.

Conversely, sun protection was thought to be associated with a modest decrease in the prevalence of osteoporotic features.

“Future studies accounting for the type, strength, and amount of sunscreen use, as well as serum vitamin D status, are needed to further explore the thus far reassuring association be-tween sun protection and bone health,” the team wrote.

The study, “Association of Sun-Protective Behaviors With Bone Mineral Densityand Osteoporotic Bone Fractures in US Adults,” was published online in JAMA Dermatology.