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

Ital J Pediatr. 2014 Jun 5;40:54. doi: 10.1186/1824-7288-40-54.

Abstract

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.

Publication types

  • Comparative Study

MeSH terms

  • Adolescent
  • Body Mass Index
  • Child
  • Confidence Intervals
  • Cross-Sectional Studies
  • Female
  • Follow-Up Studies
  • Humans
  • Italy / epidemiology
  • Male
  • Odds Ratio
  • Parathyroid Hormone / blood*
  • Prevalence
  • Reference Values
  • Retrospective Studies
  • Risk Factors
  • Vitamin D / analogs & derivatives*
  • Vitamin D / blood
  • Vitamin D Deficiency / blood
  • Vitamin D Deficiency / epidemiology*
  • Young Adult

Substances

  • Parathyroid Hormone
  • Vitamin D
  • 25-hydroxyvitamin D