Vitamin D Levels in Patients Presenting to a Rheumatology Clinic in Germany: Associations with Patient Characteristics and Season

Abstract

Background: High rates of vitamin D deficiency have been reported in population-based studies, including those conducted in Germany. The goal of this study was to evaluate vitamin D levels and associated factors in a clinical cohort of German patients presenting to a rheumatology clinic. Methods: We conducted a retrospective observational study of electronic health record data from patients presenting to a rheumatology clinic in southern Germany. Data included demographic characteristics and vitamin D levels as measured by the Elecsys^® Vitamin D total III assay (Roche). Associations between vitamin D levels and patient characteristics were evaluated by Pearson correlation analyses, t-tests, and multiple regression analyses. We also explored seasonal changes. Results: A total of 4979 patients were included; 3230 (64.9%) were female and the mean (standard deviation [SD]) age was 53.6 (15.2) years. The mean (SD) vitamin D level was 27.4 (14.0) ng/mL (range, 3-240 ng/mL). Overall, 1540 (30.9%) had vitamin D levels in the deficient range (<20 ng/mL), 1774 (35.6%) had sufficient vitamin D (20 to 30 ng/mL), 1597 (32.1%) had optimal vitamin D levels (>30 to 70 ng/mL), and 68 (1.4%) had levels >70 ng/mL. Lower vitamin D levels were significantly associated with younger age, male sex, and higher body mass index. Mean levels were significantly lower during winter months and the percentages of patients with vitamin D deficiency were higher. Conclusions: Our data indicate that low levels of vitamin D are common in clinical cohorts, particularly in men, younger adults, overweight individuals, and during winter months. Patient education and/or supplementation may help to address this issue and potentially improve patient health.

Keywords: electronic health records; epidemiology; rheumatology; seasons; vitamin D; vitamin D deficiency.

Figure 1

Vitamin D status of clinic patients. ULN, upper limit of normal.

Figure 2

Vitamin D status over the months of the year. (A) Mean vitamin D values (error bars indicate the upper and lower 95% confidence interval limits); (B) proportion of patients deficient in vitamin D (<20 ng/mL). The numbers of patients tested in each month (n) are shown in the middle of the figure.

Figure 3

Significant differences between vitamin D levels in different months of the year. The numbers of patients providing data for each month can be found in Figure 2. Mean vitamin D levels for each month were compared with those in the other months with Bonferroni post hoc tests. Red shading indicates that the month shown on the left had significantly lower mean values than the month at the top. Blue shading indicates that the month shown on the left had significantly higher mean values than the month at the top. NS, not significant.