Vitamin D deficiency 4X more likely in Italian teens if: dark skin, winter, obese, little sun, or use sunscreen – June 2014

Prevalence of hypovitaminosis D and predictors of vitamin D status in Italian healthy adolescents

Italian Journal of Pediatrics 2014, 40:54 doi:10.1186/1824-7288-40-54
Francesco Vierucci, Marta Del Pistoia, Margherita Fanos, Paola Erba and Giuseppe Saggese

Background
Vitamin D plays an important role in health promotion during adolescence. Vitamin D deficiency and insufficiency are common in adolescents worldwide. Few data on vitamin D status and risk factors for hypovitaminosis D in Italian adolescents are currently available.

Methods
25-hydroxyvitamin D (25-OH-D) and parathyroid hormone (PTH) levels were evaluated in 427 Italian healthy adolescents (10.0-21.0 years). We used the following cut-off of 25-OH-D to define vitamin D status: deficiency < 50 nmol/L; insufficiency 50-75 nmol/L; sufficiency >= 75 nmol/L. Hypovitaminosis D was defined as 25-OH-D levels < 75.0 nmol/L and severe vitamin D deficiency as 25-OH-D levels < 25.0 nmol/L. We evaluated gender, residence, season of blood withdrawal, ethnicity, weight status, sun exposure, use of sunscreens, outdoor physical activity, and history of fractures as predictors of vitamin D status.

Results
Enrolled adolescents had a median serum 25-OH-D level of 50.0 nmol/L, range 8.1-174.7, with 82.2% having hypovitaminosis D. Vitamin D deficiency and insufficiency were detected in 49.9% and 32.3% of adolescents, respectively. Among those with deficiency, 38 subjects were severely deficient (38/427, 8.9% of the entire sample). Non-white adolescents had a higher prevalence of severe vitamin D deficiency than white subjects (6/17-35.3% vs 32/410-7.8% respectively, p = 0.002). Logistic regression showed increased risk of hypovitaminosis D as follows:

  • blood withdrawal taken in winter-spring (Odds ratio (OR) 5.64) compared to summer-fall period;
  • overweight-obese adolescents (OR 3.89) compared to subjects with normal body mass index (BMI);
  • low sun exposure (OR 5.94) compared to moderate-good exposure and
  • regular use of sunscreens (OR 5.89) compared to non regular use.
  • Adolescents who performed < 3 hours/week of outdoor exercise had higher prevalence of hypovitaminosis D.

Gender, residence, and history of fractures were not associated with vitamin D status. Serum 25-OH-D levels were inversely related to PTH (r = -0.387, p < 0.0001) and BMI-SDS (r = -0.141, p = 0.007). 44/427 (10.3%) adolescents showed secondary hyperparathyroidism.

Conclusions
Italian adolescents have high prevalence of vitamin D deficiency and insufficiency. Pediatricians should tackle predictors of vitamin D status, favoring a healthier lifestyle and promoting supplementation in the groups at higher risk of hypovitaminosis D.

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