**1. Introduction**

Vitamin D (Vit D) plays an important role in normal physiological function and is essential for bone mineralization [1]. Recently, Vit D deficiency is under consideration due to the fact that it has been associated with cardiovascular disorders, malignancy, fractures and deaths [2–4]. Vit D deficiency represents an important public health concern which is commonly observed worldwide [5–7]. Vit D deficiency remains an underrecognized problem in the general populace and is poorly defined in elderly patients. This phenomenon results from reduced capacity of the skin to produce vitamin D, low skin exposure, skin pigmentation, sunscreen use, skin covering clothes and a diet low in fish and dairy products. In the elderly the reduced dermal synthesis of vitamin D is unlikely to be compensated by dietary intake of vitamin D.

In a geriatric population, Vit D deficiency has been associated with poor muscular, physical and cognitive physical performance as well as falls and fractures [8]. In a study of community dwelling persons, performed in the Chianti area in the centre of Italy which has a mild pleasant climate and sunlit rural areas, Vit D deficiency was found to be significantly high. Vitamin D levels (VDL) noticeably lessens with age in both males and females alike, but then the decline starts substantiality earlier and is sharper in females starting from the perimenopausal age. In males the decline in vitamin D levels becomes apparent 20 years later starting from their 70s, Vit D deficiency is significantly associated with aging and elderly patients who need hospitalization for longer periods and as a result more susceptible [9, 10].

Advanced age and low exposure to sunlight are the major factors associated with Vit D deficiency. Van der Wielen et al. [11] found that regardless of geographical location, free-living elderly (>70 years) living in 11 European countries are at substantial risk of inadequate Vit D status during winter and spring time and in the oldest and more obese subjects. In fact, 86% of these subjects with multiple risk factors were vitamin D deficient. Several studies have reported Vit D deficiency among different populations from the Middle East [12–15].

A report from Kuwait showed subclinical Vit D deficiency among veiled women [16]. Also, reports from Saudi Arabia demonstrated higher Vit D deficiency in Saudi women. The authors found female gender, sedentary lifestyle and low milk consumption to be independently associated with lower Vit D levels [17].

In a previous study from Qatar, El-Menyar et al. reported a high percentage (91%) of low Vit D level (<30 ng/ml) in adults (mean age: 49 ±12 years); they also found a strong association between low Vit D and hypertension [14]. Several studies addressed the association between low Vit D and high triglyceride (TG) levels, low levels of high density lipoprotein (HDL-C) and the quality of HDL [18]. Furthermore, the interference of 'Vit D' in cholesterol synthesis and potential synergistic action with statins has been reported [18].

Vit D also plays a role in insulin secretion and therefore is associated with type 2 diabetes mellitus (T2DM). Earlier studies suggested a significantly higher risk of T2DM in Vit D–deficient patients [19, 20]. In contrast, Hidayat et al. [21] observed no significant association between the incidence of T2DM and Vit D deficiency in an older population. Vit D insufficiency is frequently associated with abnormal bone metabolism including secondary hyperparathyroidism which leads to increase in bone turn over and bone loss particularly cortical bone. Patients with chronic kidney disease (CKD) have an exceptionally high rate of Vit D deficiency that is further exacerbated by their reduced ability to convert 25-(OH) Vit D into the active form: 1,25 dihydroxy-Vit D [22]. There are no studies in the elderly population in the Gulf region. Therefore, the present study was designed to assess the prevalence of Vit D deficiency and the associated risk factors among the geriatric population in Qatar.
