Stable Rates of Low Vitamin D Status Among Children Despite Increased Testing: A Population-Based Study

To determine the trends in testing and incidence of vitamin D deficiency/insufficiency in Olmsted County, Minnesota over a 16-year period.

The Rochester Epidemiology Project (REP) was used to identify Olmsted County, Minnesota residents aged <19 years who had 25-hydroxyvitamin D [25(OH)D] levels measured between January 2, 2002 and December 31, 2017. Using each patient's first 25(OH)D measurement during this period, patients were categorized into 3 groups: <20 ng/mL, 20-50 ng/mL, and >50 ng/mL. Vitamin D deficiency/insufficiency was defined as a total 25(OH)D level of <20 ng/mL.

There was a 42-fold increase in the proportion of the county's pediatric population tested each year, starting at 3.7 per 10 000 persons in 2002 and increasing to 156.1 per 10 000 persons in 2017. The largest increase in testing occurred in children aged ≥10 years, specifically the females in this age group, in whom we observed a 90-fold increase from 2002 to 2017. During the 16-year period, the incidence of vitamin D deficiency/insufficiency (per 10 000 persons) increased from 1.7 in 2002-2003 to 19.9 in 2016-2017, but the proportion that were tested and had vitamin D deficiency/insufficiency remained stable, with rates of 21.9% (95% CI, 16.1%-29.1%) in 2006-2007 and 18.5% (95% CI, 16.0%-21.2%) in 2016-2017.

The proportion of the county's pediatric population who underwent vitamin D testing increased from 2002 to 2017, in parallel to the increased incidence of vitamin D deficiency/insufficiency, but the proportion tested that had vitamin D deficiency/insufficiency remained stable over time.