Abstract and Introduction
Objective: Vitamin D deficiency is highly prevalent in high-risk patient populations, but the prevalence among otherwise healthy adults is less well-defined. The goal of this study was to determine the prevalence and predictors of low 25-hydroxyvitamin D [25(OH)D] levels in healthy younger adults.
Methods: This was a cross-sectional study of 634 healthy volunteers aged 18–50 years performed between January, 2006 and May, 2008. We measured serum 25(OH)D and parathyroid hormone and recorded demographic variables including age, sex, race, and use of multivitamin supplements.
Results: Thirty-nine percent of subjects had 25(OH)D ≤20 ng/mL and 64% had 25(OH)D ≤30 ng/mL. Predictors of lower 25(OH)D levels included male sex, black or Asian race, and lack of multivitamin use (P<0.001 for each predictor). Seasonal variation in 25(OH)D levels was present in the overall cohort but was not observed in multivitamin users. Lower 25(OH)D levels were associated with increased risk of elevated parathyroid hormone. Regression models predicted 25(OH)D levels ≤20 or ≤30 ng/mL with areas under the receiver operating characteristic curves of 0.76 and 0.80, respectively.
Conclusion: Low 25(OH)D levels are prevalent in healthy adults and may confer risk of skeletal disease. Black and Asian adults are at increased risk of deficiency and multivitamin use appears partially protective. Our models predicting low 25(OH)D levels may guide decision-making regarding whom to screen for vitamin D deficiency.
Vitamin D is critical for bone health. Vitamin D deficiency causes impaired calcium absorption which can lead to rickets and osteomalacia.[1–3] Additionally, vitamin D deficiency is associated with osteoporosis and an increased risk of fractures.[4–6] Finally, accumulating observational evidence suggests that low vitamin D levels are associated with extraskeletal sequelae including increased risks of cancer, cardiovascular disease, infection, and autoimmune disease.
Serum 25-hydroxyvitamin D [25(OH)D] levels reflect body stores of vitamin D. A substantial fraction of the United States population has low 25(OH)D levels. For example, in a recent population-based National Health and Nutrition Examination Survey from 2001 to 2006, 32% of participants had serum 25(OH)D levels ≤20 ng/mL. Multiple populations are at particularly high risk for vitamin D deficiency, including children, the elderly, and people with increased skin pigmentation.[8–10] Recommendations regarding whom to screen vary, though most experts suggest screening only populations at higher risk.[11,12] The use of vitamin D-containing supplements is associated with increased 25(OH)D levels, thereby decreasing the likelihood of deficiency, however, recommendations regarding optimal supplement dose also vary widely.[9,12–14]
We hypothesized that, in a population lacking significant risk factors, low vitamin D levels would, nonetheless, be highly prevalent. Because of the logistical and economic challenges associated with universal screening, we sought to identify demographic and behavioral factors predictive of low vitamin D levels that are easily assessed in a clinical setting.
Endocr Pract. 2012;18(6):914-923. © 2012 American Association of Clinical Endocrinologists