Socio-economic determinants of vitamin D deficiency in the older Polish population: results from the PolSenior study.

OBJECTIVE: Numerous studies have reported an association between vitamin D (25-hydroxyvitamin D; 25(OH)D) deficiency and low economic status, lower educational level, drugs exposure, smoking and reduced physical activity. Our study analysed the association between sociodemographic factors and 25(OH)D status in Polish (Caucasian) seniors. DESIGN: Cross-sectional study (part of the PolSenior study). Serum 25(OH)D concentration was measured by a solid-phase ELISA method; a standardized questionnaire evaluated educational level, economic status, alcohol consumption, current or past cigarette smoking, physical activity, activities of daily living (ADL) and instrumental activities of daily living. SETTING: Community-dwelling randomly selected individuals aged 65 years or older, selected using three-stage stratified, proportional draw. SUBJECTS: Seniors (n 3472; 1658 women and 1814 men). RESULTS: Mean serum 25(OH)D concentration was 20·5 (sd 9·6) ng/ml. Values below the recommended level (30 ng/ml) were detected in 82·8 % of men and 90·4 % of women. Regression analysis revealed that the difference between sexes was associated with decreased walking activity in women, probably resulting in less sunlight exposure. There was a positive association between any disability in ADL and the presence of vitamin D deficiency/insufficiency. In the sex-adjusted analysis, older age, alcohol abstinence and lack of cycling and long-distance walking were explanatory variables for vitamin D deficiency. CONCLUSIONS: Vitamin D deficiency/insufficiency is frequent in the older Polish population and associated with functional disability and impaired mobility of seniors.

Parathyroid hormone response to different vitamin D levels in population-based old and very-old Polish cohorts.

BACKGROUND: Low vitamin D (VD) is not always followed by the development of secondary hyperparathyroidism (SHPT). The study aimed to assess the prevalence of SHPT and functional hypoparathyroidism (FHPT) in relation to VD deficiency/insufficiency and factors predisposing to parathyroid hormone (PTH) response in old and very-old Caucasians. METHODS: A sub-study of the cross-sectional PolSenior project analyzed serum 25(OH)D, intact PTH (iPTH) and C-terminal fibroblast growth factor 23 (cFGF23) concentrations in 3472 (1658 women) individuals aged ≥65 years. SHPT was defined as iPTH concentration > 65 pg/mL, while FHPT as iPTH within the reference range in the presence of 25(OH)D < 30 ng/mL. RESULTS: SHPT was diagnosed in 426 participants (14%) and was more frequent in very-old (≥ 80 years) than in the old (65-79 years) subgroup (18.8 vs 9.8%; OR = 2.12; 95% CI: 1.72-2.62). While, FHPT was found in 2269 subjects (85.2%) with 25(OH)D < 30 ng/mL, and was more prevalent in the old than very-old subgroup (89.3 vs 80.1%; OR = 2.03; 95% CI: 1.63-2.52). Multiple regression analysis showed that age ≥ 80 years, use of loop diuretics, decreased glomerular filtration rate, higher cFGF23 level but lower calcium and phosphate concentrations, predispose for the occurrence of SHPT. CONCLUSIONS: The interrelation between 25(OH)D deficiency and PTH response is complex. In older adults, PTH response is related to VD deficiency, age, impaired kidney function, the use of loop diuretics and the levels of calcium, phosphate, and cFGF23.