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

<b>Background</b>: 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. <b>Methods</b>: 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, <i>t</i>-tests, and multiple regression analyses. We also explored seasonal changes. <b>Results</b>: 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. <b>Conclusions</b>: 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.