Assessment of prevalence of hypovitaminosis D in multiethnic population of the United Arab Emirates.

United Arab Emirates (UAE) has a high prevalence of hypovitaminosis D. Not much data are available regarding the prevalence of Vitamin D deficiency among multiethnic UAE adult population. (1) To determine the prevalence of hypovitaminosis D in multiethnic UAE population (2) To compare the Vitamin D status in Arab and non-Arab population (3) To identify the demographic variables associated with hypovitaminosis D. It was a retrospective study conducted at a secondary care hospital. Electronic case records of all the subjects who had checked their Vitamin D levels during the time period of May 2010-October 2012 were considered for the study. Vitamin D severe deficiency, deficiency, insufficiency, and sufficiency were defined as serum 25-hydroxy Vitamin D (25(OH)D) levels < 10 ng/mL, 10-20 ng/mL, 21-30 ng/mL, and > 30 ng/mL, respectively. A total 425 subjects were included for the data analysis. Vitamin D deficiency was diagnosed in 208 (48.9%) subjects followed by severe Vitamin D deficiency and insufficiency in 141 (33.2%) and 63 (14.8%) subjects, respectively. The overall prevalence of hypovitaminosis D was 96.9%. Negative association (r = -0.196, P < 0.01) was observed between body mass index (BMI) and 25(OH)D levels. Ethnicity was not (P = 0.103) a predictor of 25(OH)D levels. Majority of our study subjects had Vitamin D deficiency. There was no substantial difference in 25(OH)D levels of different ethnic groups. Female gender, age, and BMI were the predictors 25(OH)D levels.

INTRODUCTION

Hypovitaminosis D is considered to be the most common medical condition of rising prevalence across worldwide.[1] Around one billion people in the worldwide are known to be affected by hypovitaminosis D.[2] The prevalence rate of hypovitaminosis D varies among different countries and among different ethnic groups of the same country.[3] United Arab Emirates (UAE) has a high prevalence of hypovitaminosis D, in spite of abundant sunlight.[4]

Hypovitaminosis D is a major risk factor for the development of metabolic bone disease.[5] Several studies have reported the association among hypovitaminosis D and cardiovascular diseases, multiple sclerosis, metabolic syndrome, and diabetes mellitus.[3]

Few published studies are available on the prevalence of hypovitaminosis D in UAE multiethnic population and associated demographic variables. Hence, data collected from this preliminary study could be useful for further research in this area. With this background, the objectives of the present study were to determine the prevalence of hypovitaminosis D in multiethnic UAE population. The study also aimed at comparing the Vitamin D status in Arab and non-Arab population and to identify the demographic variables associated with hypovitaminosis D.

MATERIALS AND METHODS

This was a retrospective study conducted at a secondary care hospital of UAE. The study was approved by the Research and Ethics Committee. We reviewed the electronic case records of 425 subjects, who had checked their Vitamin D levels during the time period of May 2010–October 2012. The data of subjects of both sex aged >18 years and who were previously undiagnosed or diagnosed with Vitamin D deficiency were included. We excluded the data of those subjects whose electronic case records were incomplete, Vitamin D measurement results were contradicting and if subjects were nonresidents of UAE.

Operational definitions

Based on our laboratory reference values, Vitamin D severe deficiency, deficiency, insufficiency, and sufficiency were defined as a 25-hydroxy Vitamin D (25(OH)D) levels <10 ng/mL, 10–20 ng/mL, 21–30 ng/mL, and >30 ng/mL, respectively. This operational definition was based on the international consensus.[6] The prevalence of hypovitaminosis D was calculated based on the percentage of the total number of cases who were having hypovitaminosis D (<30 ng/mL) by the total number of cases in whom 25(OH)D levels was measured.

Statistical analysis

The data were analyzed using SPSS 20, IBM, Armonk, NY, United States of America. Continuous variables were compared using Student's t-test or one-way ANOVA. Pearson Chi-square test was used to assess the significant relationship between categorical variables and 25(OH)D levels. Pearson correlation test was applied to examine the association between continuous demographic variables and Vitamin D levels. Multiple regression analysis was done to examine the effect of variables on Vitamin D levels.

RESULTS

A total of 425 subjects satisfying inclusion criteria were included for the data analysis. Good number of study population was males 243 (57.2%). Majority of our study subjects were Indians 228 (53.6%) [Table 1].

Table 1

Demographic variables and mean±SD 25-hydroxy Vitamin D levels

25-hydroxy Vitamin D levels of study subjects

The mean 25(OH)D levels of the study subjects were 14.0 ± 8.1 ng/mL. Vitamin D deficiency, severe deficiency, and insufficiency were diagnosed in 208 (48.9%), 141 (33.2%), and 63 (14.8%) subjects, respectively. The overall prevalence of hypovitaminosis D (combination of severe deficiency, deficient, or insufficiency) was found to be 96.9% [Table 2].

Table 2

Association among demographic variables, symptoms of hypovitaminosis D and 25-hydroxy Vitamin D levels

Symptoms of hypovitaminosis D

Majority 287 (67.5%) were having generalized pain and weakness. It is interesting to note that 101 (23.8%) subjects were asymptomatic [Table 2].

Presence of comorbidities

Hypertension existed as the most common comorbidity affecting 249 (58.6%) subjects, followed by dyslipidemia in 246 (57.9%) subjects [Figure 1].

Figure 1

Associated comorbidities present in study population

Gender and 25-hydroxy Vitamin D levels

The 25(OH)D levels of males (15.3 ± 8.3 ng/mL) were significantly higher (P < 0.05) than females (12.3 ± 7.2 ng/mL) [Table 1]. There was a significant relationship between the gender and Vitamin D levels (χ2 = 13.1, df = 3, P = 0.004) [Table 2].

Ethnicity and 25-hydroxy Vitamin D levels

There was no significant difference (P = 0.059) in the mean 25(OH)D levels of subjects of different ethnic background [Table 1]. However, we observed a significant relationship between ethnicity and 25(OH)D levels (χ2 = 37.60, df = 18, P = 0.004) [Table 2].

Age and 25-hydroxy Vitamin D levels

The mean 25(OH)D levels of subjects belonging to age group of 21–30 years was lower (10.8 ± 5.1ng/mL) compared to other age groups [Table 1]. There was no statistically significant relationship (P > 0.05) between 25(OH)D levels and age (χ2 = 23.2, df = 15, P = 0.08) [Table 2].

ANOVA showed a significant difference (P = 0.022) in the 25(OH)D levels of subjects belonging to different age groups. However, post hoc analysis by Bonferroni showed only significant difference (P = 0.041) in subjects belonging to 21–30 years (10.8 ± 5.1 ng/mL) and 50–60 years (15.8 ± 8.3 ng/mL) [Table 1].

Body mass index and 25-hydroxy Vitamin D levels

There was a significant difference (P = 0.001) in the mean 25(OH)D levels of subjects with body mass index (BMI) <25 kg/m2 (16.5 ± 8.6 ng/mL) and > 25 kg/m2 (13.2 ± 8.0 ng/mL) [Table 1].

Symptoms of hypovitaminosis D and 25-hydroxy Vitamin D levels

A significant association (P < 0.05) was documented among 25(OH)D levels and back ache (χ2 = 15.73, df = 3, P = 0.01), muscle pain (χ2 = 15.90, df = 3, P = 0.001), muscle weakness (χ2 = 12.33, df = 3, P = 0.006), generalized aches/weakness (χ2 = 28.74, df = 3, P < 0.01), and in subjects without any symptoms (χ2 = 9.25, df = 3, P = 0.026) [Table 2].

Association among age, height, weight, body mass index, and 25-hydroxy Vitamin D levels

A significant (r = 0.130, P = 0.008) positive association was detected between the age and 25(OH)D levels of the subjects. Whereas significant (r = −0.196, P < 0.01) negative association was also noticed between BMI and Vitamin D levels [Table 3].

Table 3

Correlation among continuous demographic, clinical variables, and 25-hydroxy Vitamin D levels

Predictors of 25-hydroxy Vitamin D levels

BMI (R2 = 0.077, f (4, 351) =7.33, Beta = −0.202, P < 0.01) and gender (R2 = 0.077, f (4, 351) =7.33, Beta = −0.179, P = 0.027) were significant negative predictors of 25(OH)D levels. Whereas, age was a significant positive predictor (Beta = 0.117, P = 0.031) and ethnicity had no influence on 25(OH)D levels [Table 4].

Table 4

Multivariate regression analysis of the variables and 25-hydroxy Vitamin D levels

DISCUSSION

The overall prevalence of hypovitaminosis D documented in our study is in agreement with the findings of another study, which reported 90.5% prevalence among UAE women.[7] The prevalence hypovitaminosis D in different Middle-East and Asian countries is found to be 35–68.8%.[89] Our findings were consistent with overall prevalence data of hypovitaminosis D in India (50–90%) and Pakistan (85–98%).[1011] A good number of our study populations were Indian and Pakistani residents.

The prevalence of hypovitaminosis D documented in our study was found to be higher than reports from different Middle-East countries.[89] This could be due to dissimilarity in age, gender, race, dressing pattern (veil vs. nonveil), cultural practice, geographic region, food habit, skin tone, exposure to sun, sunscreen usage, type of the study sample (healthy population vs. diseased), sample size, and difference in the 25(OH)D reference ranges or cut-off values.[912]

Mean 25(OH)D levels were lower (P < 0.05) in female subjects. Lower levels of Vitamin D are also reported in other studies.[13] In contrast, a study reported significantly (P < 0.001) lower mean 25(OH)D concentrations in morbidly obese males. The lower 25(OH)D levels among women may be because of lack of exposure to sunlight, less time spent outdoor, and dressing pattern due to sociocultural or religious reasons.[14]

Generalized body aches/weakness and muscle pain were the most common symptoms reported by the patients. Similar observations have been reported in other studies.[15] A multiethnic Norwegian study identified nonspecific musculoskeletal pain, headache, or fatigue as the common symptoms.[16] Studies have reported that 26–100% patients with a presenting symptom of musculoskeletal pain are likely to have hypovitaminosis D.[17]

In accordance with our findings, other studies have also reported hypertension as the most common risk factor followed by dyslipidemia and diabetes.[18] Another study reported hyperglycemia and dyslipidemia as the most prevalent comorbidities followed by central obesity and hypertension.[19]

In line with our findings, other studies have also reported a higher prevalence of hypovitaminosis D in middle-aged subjects.[20] In contrast to our findings, other studies have reported predominance in diverse age groups.[1321] This difference in the prevalence might be due to the fact that majority of our samples were in the age group 41–50 years.

Vitamin D deficiency occurs in all age groups ranging from children to elderly.[22] However, the cutaneous production of Vitamin D and ability to synthesize Vitamin D decreases with the age.[23] In spite of this, it is interesting to note that age was positively correlated with 25(OH)D levels in our study. This finding is in accordance with other studies from Middle-East Countries, which reported a positive correlation between age and Vitamin D levels.[24]

We noticed a higher 25(OH)D levels in the age group of 51–60 years. Our study population also consisted of previously diagnosed hypovitaminosis D subjects, who might have already received parenteral Vitamin D therapy. This could be the reason for higher 25(OH)D levels in this age group.[25] In contrast, studies have also documented an inverse association.[26] Whereas few studies have not documented any correlation between age and 25(OH)D levels.[27]

Our findings were in accordance with other studies, which reported significant decrease in 25(OH)D levels with increasing BMI.[28] However, a meta-analysis study showed a significant inverse weak association between Vitamin D levels and BMI in adult men.[29] On the contrary, few studies found no association.[30] The postulated reasons for low levels of 25(OH)D levels in obese patients are multifactorial such as decreased bioavailability of Vitamin D, excessive storage of Vitamin D in adipose tissue, elevated parathyroid hormone levels, decreased mobility, and breakdown of vitamin due to increased oxidative reactions in adipose tissue.[31]

No significant difference (P > 0.05) in the Vitamin D levels of different ethnic groups was observed in our study. In contrast, few studies conducted in other parts of the world have documented difference among different ethnic groups or races.[32] However, few studies did not document any such difference.[33] The proposed reasons for difference in the findings could be due to skin color, sun exposure, latitude, or region in which the subjects are living have been stated in the literature.[34]

The main limitations of our study were that the results were based on the single measurement of 25(OH)D levels and was limited to subjects visiting single center, which may not be the complete representation of the different ethnic groups living in UAE. Since ours was a retrospective study, we could not obtain information on skin exposure time, dressing pattern, and food habit details. Hence, we could not present these data in our study.

CONCLUSION

Higher prevalence of hypovitaminosis was observed in males when compared to females. There was no significant difference in the Vitamin D levels of different ethnic groups. Hypertension was the most commonly observed comorbidity in the study subjects. A negative association was documented between BMI of the subjects and 25(OH)D levels. BMI was the negative predictor of 25(OH)D levels.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.