Assessing Serum Concentrations of 25-Hydroxy-Vitamin D in North-Western Italy

Backgound: Most of the published studies on vitamin D levels in Italy have been performed in specific age- or disease- subgroups. Few data are available on the status of vitamin D in the adult general population.

We report on vitamin D levels of a large sample of adults from North-Western Italy. Association with age, sex, and season is also evaluated.

13,110 cases (24% men, 76% women; median age 67 [interquartile range, IQR, 56-77] years old) were collected in the North-Eastern of Piedmont (Italy).

25-OH-vitamin D levels were measured by chemiluminescent immunoassay.

Median total vitamin D level was 19.9 ng/ml (IQR 11.2-28.8 ng/ml) with up to 3,592 (27.4%) and 10,185 (77.7%) subjects respectively below 12 and 30 ng/ml. Vitamin D levels were significantly higher in women than in men (20.5 vs 18.1 ng/ml; p<0.001), in summer than in winter (21.4 vs 18.5 ng/ml; p<0.001), and in individuals aged ≤45years or 46-64 years than in those older than 65 years (20.3 and 21.3 vs 18.8 ng/ml). The lowest mean vitamin D levels were reported during the winter season by men aged ≥65 years (14.7 ng/ml) and 46-64 years (16.8 ng/ml). Multivariate analysis confirmed that age (p<0.001), sex (p=0.002), season (p<0.001) and their interaction (p=0.03) were independently associated to vitamin D concentrations.

This study clearly shows that the majority of adult Italian population, living in a sunny and highly urbanized area of North-Western Italy, have an important deficiency in vitamin D. However, these data must be interpreted with caution if considering the lack of standardization of vitamin D assays.