Sun-protective behaviors are not associated with decreased bone mineral density.
Clinical Pearls:
This study was a population-based cross-sectional study of adults who participated in the National Health and Nutrition Examination Survey (NHANES) between 2017-2018
Authors found that, in a multivariate model, the bone-mineral density z-scores were not statistically significantly associated with the use of “individual sun-protective behaviors” [e.g. seeking shade (-0.23, 95% confidence interval -0.47 to 0.02, P = .18), wearing long-sleeves (-0.08, 95%CI -0.27 to -0.12, P=.72), and sunscreen use (-0.10, 95%CI -0.32 to 0.13, P = .15)].
Among 3418 adults with an average age of 39.5 (95%CI 38.6-40.4), the prevalence of “frequent” sun-protective behavior was 31.6% for staying in shade, 11.8% for wearing long sleeves, and 26.1% for sunscreen use.
Discussion:
As dermatologists and physicians, it is important to educate patients not only on ways to protect their skin but also about methods to support their overall health as well. While the skin provides a direct route for the metabolization and activation of vitamin D, direct and indirect UV exposure have grave consequences for skin health in terms of photoaging as well as developing melanoma and nonmelanoma skin cancer (NMSC).
This study provides a current cross-sectional, population-based investigation of the potential association between sun-protective behaviors among adults and a) bone mineral density (BMD) and b) osteoporotic fractures. Importantly this study provided additional granular demographic information including race and ethnicity, socioeconomic data, country of birth (i.e., US vs ex-US), lifestyle considerations (milk consumption, BMI) along with individual dermatologic history (e.g. phototype, history of sunburns). After adjusting for demographic and medical confounders, multivariate analysis found decreased slight decrease in total lumbar spine BMD and “moderate” sunscreen use (-0.35, 95%CI -0.56 to -0.14, p = .01), however multivariate adjusted moderate-frequent “staying in the shade” were associated with decreased prevalence of osteoporotic spine fractures (OR 0.13-0.19, p = .02).
Limitations of this study include inability to draw causal relationships given its cross-sectional nature, and inherent limitation in questionnaire design (e.g., failure to distinguish types of sunscreen product, amount of sunscreen used, delineation in frequency of sunscreen use, shade-seeking, or wearing long sleeves, etc).
Despite these limitations, these findings provide a launching point not only for additional prospective studies, but also for patient education. The study noted not only did less than a third of participants frequently use sun-protective behavior, but many also cited a lack of physician-patient communication as a reason for lack of sun-safe knowledge (including a third who did not know about the risks of melanoma). It is important that dermatologists counsel patients on appropriate lifestyle modifications that promote overall health in addition to sun-safe practices.
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