Changing Incidence of Serum 25-Hydroxyvitamin D Values Above 50 ng/mL: A 10-Year Population-Based Study.
Level 3 - non-randomized controlled study
Retrospective population-based cohort study
PubMed 25939935 · doi:10.1016/j.mayocp.2015.02.012
What was done
Researchers conducted a retrospective population-based study using the Rochester Epidemiology Project in Olmsted County, Minnesota, spanning January 1, 2002, through December 31, 2011. They tracked the incidence of serum 25-hydroxyvitamin D [25(OH)D] concentrations above 50 ng/mL and evaluated potential hypercalcemia occurring within 3 months of the index measurement via medical record review.
What was found
Across 20,308 total measurements, 1,714 (8.4%), 123 (0.6%), and 37 (0.2%) unique individuals had 25(OH)D concentrations >50 ng/mL, ≥80 ng/mL, and ≥100 ng/mL, respectively. The age- and sex-adjusted incidence of 25(OH)D levels >50 ng/mL rose from 9 to 233 per 100,000 person-years between 2002 and 2011 (P<.001), with the greatest increases in women (P<.001) and individuals aged 65 and older (P<.001). Serum 25(OH)D levels were not significantly associated with serum calcium concentrations (P=.20) or risk of hypercalcemia (P=.24). Only 4 patients (0.2%) had hypercalcemia temporally linked to high 25(OH)D, and only 1 individual had confirmed clinical toxicity (at 364 ng/mL).
Why it matters
Despite a sharp rise in high 25(OH)D levels due to increased supplementation and testing over the decade, high serum concentrations rarely resulted in hypercalcemia or acute clinical toxicity.
Limits
The study was confined to a single geographic county with limited demographic diversity. Testing was done as part of routine clinical care rather than universal population screening, introducing potential indication bias. Chart review for toxicity was limited to individuals with measured calcium within 3 months of the 25(OH)D test.
Cited by
- supports A study of 20,000 patients in the Mayo Clinic database taking vitamin D doses up to 55,000 IU/day identified only one case of hypercalcemia, in an individual with serum levels between 200–300 ng/mL.