The prevalence of vitamin D deficiency varies across countries and few data exist in the adult population in Greece.
To assess vitamin D levels in unselected patients from primary care and to investigate possible correlations with clinical, seasonal, and quality-of-life parameters.
In this cross-sectional study, 389 consecutive patients were included. They were grouped according to vitamin D status as vitamin D deficient (<20 ng/mL) and vitamin D sufficient groups (≥20 ng/mL). Demographic, Epworth Sleepiness Scale (ESS), Athens Insomnia Scale (AIS), Beck Depression Inventory (BDI), and Fatigue Severity Scale (FSS) scores were measured and compared between groups.
Vitamin D deficiency (10; OR = 3.345, 95% CI = 1.124-9.948, P = 0.029), depressive symptoms (BDI >10; OR = 3.769, 95% CI = 0.984-14.443, P = 0.04), and fatigue (FSS >36; OR = 7.157, 95% CI = 0.855-59.877, P = 0.04) showed significant independent associations with vitamin D deficiency in specific subgroups of patients.
A large proportion of patients in primary care had vitamin D deficiency, independently associated with hypertension, sleepiness, depressive symptoms, and fatigue. Further research is needed in order to determine the role of vitamin D in these patients.

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