Abstract
Sunlight-induced vitamin D, synthesis in the skin is the major source of vitamin D, but data on the relationship of sun-related behaviour with vitamin D and parathyroid hormone (PTH) levels are relatively sparse. We evaluated whether habitual sun exposure is associated with 25-hydroxyvitamin D (25[OH]D) and PTH levels and whether there exist seasonal variations. We examined 111 hypertensive patients in Austria (latitude 47° N). Frequent sunbathing at home and outdoor sports were associated with higher 25(OH)D levels (P < 0.05 for both). Red or blond scalp hair as a child, memory of sunburns, preferring sunbathing, frequent stays on the beach or in open-air pools, and solarium use were associated with lower PTH levels (P < 0.05 for all). Multiple linear regression analyses including age, sex, and body mass index showed that sun exposure score was significantly associated with 25(OH)D (beta coefficient = 0.27; P = 0.004) and by trend with PTH (beta coefficient = −0.16; P = 0.09). These associations were more prominent in summer in which 25(OH)D levels were significantly higher compared to winter. Translation of these findings into recommendations for the prevention and treatment of vitamin D deficiency remains a challenge for the future.
Highlights
Vitamin D deficiency is considered a widespread public health problem because vitamin D is important for musculoskeletal health and probably for various other chronic diseases including cardiovascular and metabolic diseases, cancer, and infections and autoimmune diseases [1,2,3,4,5,6,7,8,9,10]
Associations of 25(OH)D and parathyroid hormone (PTH) with answer scores of the sun behaviour questionnaire are shown in Tables 2 and 3, respectively. 25(OH)D levels were significantly increased in patients who reported on outdoor sports and sunbathing at home
PTH levels were significantly decreased in participants with a red or blond scalp hair as a child, in those who could recall sunburns and in those who like sunbathing and who reported on frequent stays at the beach or open-air pools and on solarium use
Summary
Vitamin D deficiency is considered a widespread public health problem because vitamin D is important for musculoskeletal health and probably for various other chronic diseases including cardiovascular and metabolic diseases, cancer, and infections and autoimmune diseases [1,2,3,4,5,6,7,8,9,10]. The currently high worldwide prevalence of vitamin D deficiency is mainly attributable to low sunlight exposure of the skin [1,2,3, 11]. Previous studies suggest that ∼80% of vitamin D is obtained by ultraviolet-B- (UV-B-) induced vitamin D synthesis in the skin whereas diet makes only a minor contribution [12]. There remain various ambiguous issues regarding the impact of habitual sunlight exposure on vitamin D status. Previous data on this topic are relatively
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