Vitamin D deficiency is a problem for adult out-patients? A university hospital sample in Istanbul, Turkey

Objective: To investigate the frequency of vitamin D deficiency in relation to demographics, clinical diagnosis, season of measurement and laboratory parameters in adult out-patients. Design: Descriptive, retrospective study concerning evaluation of the initial 25-hydroxyvitamin D (25(OH) D) levels determined at admission in relation to demographics, clinical diagnosis, season of measurement and laboratory parameters. 25(OH)D levels,20 ng/ml were classified as deficiency, 20-30 ng/ml as insufficiency and > 30 ng/ml as sufficiency. Setting: Out-patient clinics at a tertiary care centre. Subjects: A total of 2488 adult patients (mean age: 53.3 (SD 15.2) years; 85.2% were females) admitted to out-patient clinics at Baskent University Istanbul Hospital were included. Results: Mean level of 25(OH) D in the overall population was 17.4 (SD 11.5) ng/ml while insufficiency and deficiency were evident in 24% and 66% of patients, respectively. Mean 25(OH) D levels in males > 45 years old were higher than in their female counterparts (19.4 (SD 11.3) ng/ml v. 17.8 (SD 12.2) ng/ml; P < 0.05). Mean 25(OH) D levels obtained in summer (18.6 (SD 11.1) ng/ml) and autumn (23.3 (SD 13.6) ng/ml) were significantly higher than levels in spring (16.1 (SD 10.3) ng/ml) and winter (14.6 (SD 10.2) ng/ml; P < 0.01). Mean 25(OH) D levels were determined to be significantly lower in obese patients compared with non-obese patients (15.6 (SD 10.4) ng/ml v. 17.6 (SD 11.6) ng/ml; P < 0.05). Levels of 25(OH) D were significantly negatively correlated with serum parathyroid hormone levels (r=-0.194; P < 0.001) while significantly positively correlated with phosphorus (r=0.059; P < 0.01) and HDL cholesterol (r=0.070; P < 0.01) levels. Conclusions: Our findings indicate that vitamin D deficiency is very common among out-patients in Turkey, regardless of gender and age, especially among obese people and during winter and spring.