Sun exposure questionnaire predicts circulating 25-hydroxyvitamin D concentrations in Caucasian hospital workers in southern Italy

Introduction: Recent sun exposure should correlate with circulating 25-hydroxyvitamin D [25(OH)D] due to ultraviolet B (UVB)-catalyzed cutaneous synthesis of vitamin D. Methods: A Sun Exposure Score was calculated for healthy adults using a recall questionnaire assessing daily Time in Sun (30. min) and Skin Exposure (face/hands; face/hands and arms; face/hands and legs; and " bathing suit" ) for 1 week in each of the winter and summer (n=47 and 23, respectively; n=18 participated in both). Concentrations of 25(OH)D were measured by DiaSorin RIA on end-of-week sera. Results: Mean serum 25(OH)D was higher in summer than winter (58.6 ± 16.5 nmol/L vs 38.8 ± 29.0. nmol/L, respectively, P=0.003 unpaired). The calculated Sun Exposure Score correlated strongly with serum 25(OH)D during summer (Spearman's rho. =0.59, P=0.003); based on the Pearson coefficient of determination, summer Sun Exposure Score explained 38% of the variability in summer serum 25(OH)D. The Sun Exposure Score did not correlate with 25(OH)D in the winter (rho. =0.19, P=0.210). The summer correlation was largely explained by the Time in Sun (rho. =0.58, P=0.004) rather than area of Skin Exposed (rho. =0.10, P=0.660). Although there was a correlation between winter and summer Sun Exposure Scores (rho. =0.63, P=0.005), there was no summer vs. winter correlation in serum 25(OH)D (rho. =0.08, P=0.76). Conclusion: This simple 1-week sun exposure recall questionnaire predicted summer serum 25(OH)D concentrations, accounting for 38% of the variability in 25(OH)D among healthy Italian adults.