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 Table of Contents  
Year : 2023  |  Volume : 2  |  Issue : 1  |  Page : 29-34

Comparison of Vitamin D Status between Resident and Nonresident Bangladeshis with Type 2 Diabetes Mellitus: A Single-Center, Cross-Sectional Study

1 Department of Medicine, Army Medical College, Cumilla, Bangladesh
2 Department of Psychiatry, Cumilla Medical College Hospital, Cumilla, Bangladesh
3 Department of Endocrinology, Mymensingh Medical College, Mymensingh, Bangladesh

Date of Submission30-Nov-2022
Date of Acceptance25-Dec-2022
Date of Web Publication23-Jan-2023

Correspondence Address:
A B. M Kamrul-Hasan
Department of Endocrinology, Mymensingh Medical College, Mymensingh-2200
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/bjem.bjem_18_22

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Background and Objectives: Vitamin D deficiency (VDD) is highly prevalent in both healthy population and patients with type 2 diabetes mellitus (T2DM) in Bangladesh. Data on Vitamin D status in nonresident Bangladeshi (NRB) individuals with T2DM are scarce. We conducted this study to compare the Vitamin D status between resident and NRBs. Materials and Methods: This cross-sectional study evaluated 234 patients with T2DM (109 resident Bangladeshis [RBs] and 125 NRBs) attending a specialized diabetes hospital in Cumilla city, Bangladesh, from July 2021 to February 2022. Serum 25(OH)D <20 ng/mL defined VDD. Results: The mean age of the study participants was 42.5 ± 9.4 years; the frequencies of obesity, hypertension, dyslipidemia, and uncontrolled diabetes (HbA1c ≥7%) were 79.1%, 45.7%, 93.6%, and 88.9%, respectively. The Middle East countries were the residing countries of most (92.8%) of the NRBs. Higher frequencies of smokers and dyslipidemia were observed among RBs. The body mass index and HbA1c were higher, and low-density lipoprotein cholesterol was lower among NRBs than RBs. In the study participants, the mean 25(OH)D level was 25.7 ± 10.2 ng/mL; 30.3%, 38.5%, and 31.2% of the study participants were sufficient, insufficient, and deficient in Vitamin D, respectively. RBs and NRBs had similar 25(OH)D levels (25.7 ± 11.9 vs. 25.8 ± 8.5 ng/mL, P = 0.948) and VDD status (36.7% vs. 26.4%, P = 0.124). Conclusion: Low Vitamin D is highly prevalent in both RBs and NRBs with T2DM though they have similar Vitamin D levels and comparable rates of VDD. Further studies are needed to determine the factors that influence Vitamin D status in our people.

Keywords: Nonresident Bangladeshis, type 2 diabetes, Vitamin D, Vitamin D deficiency

How to cite this article:
Alam MS, Kalam ST, Saha R, Kamrul-Hasan A B. Comparison of Vitamin D Status between Resident and Nonresident Bangladeshis with Type 2 Diabetes Mellitus: A Single-Center, Cross-Sectional Study. Bangladesh J Endocrinol Metab 2023;2:29-34

How to cite this URL:
Alam MS, Kalam ST, Saha R, Kamrul-Hasan A B. Comparison of Vitamin D Status between Resident and Nonresident Bangladeshis with Type 2 Diabetes Mellitus: A Single-Center, Cross-Sectional Study. Bangladesh J Endocrinol Metab [serial online] 2023 [cited 2023 Jun 7];2:29-34. Available from: https://www.bjem.org/text.asp?2023/2/1/29/368416

  Introduction Top

Diabetes mellitus (DM) is a metabolic disorder affecting about 537 million adults worldwide. Currently, Bangladesh ranks eighth in the world with a total of 13.1 million adults with DM, and it is estimated that by 2045, around 22.3 million of its people will have diabetes, making it seventh in the ranking at that time. Type 2 DM (T2DM) is the most common type of DM worldwide, including in Bangladesh. T2DM is multifactorial and is caused by the interplay of several environmental and genetic factors.[1] Vitamin D is a fat-soluble vitamin, mostly derived from sun exposure (i.e., synthesized in the skin) and a small amount from diets including fish, milk, yogurt, orange juice, and cereals.[2] Vitamin D plays a vital role in bone metabolism regulating the intestinal absorption of minerals such as calcium and phosphorus.[3] Vitamin D deficiency (VDD) plays a role in the onset and development of insulin resistance and T2DM.[4] Its deficiency is also associated with various cardiovascular risk factors and is linked to higher incidence and mortality of cardiovascular diseases.[5] Vitamin D is also linked to glycemic control and diabetic complications in T2DM.[6],[7]

Worldwide, VDD is emerging as a very common condition.[8] As the main source of Vitamin D is sunlight exposure, it has long been assumed that living in a sunny country ensures adequate Vitamin D levels. However, there is increasing evidence that VDD may have been underestimated in low-latitude tropical countries.[9] Although Bangladesh shares tropical and subtropical regions in their national map, the prevalence of VDD is very high (67%) according to a recent meta-analysis.[10] Studies also have reported a high prevalence of VDD in patients with T2DM in Bangladesh, which is higher than in healthy controls; Vitamin D levels are also lower in T2DM than in controls.[11],[12],[13],[14],[15]

In terms of the number of people, Bangladeshi migrants are the sixth largest in the globe. Approximately 1.2 crore workers migrated from the country to different parts of the world, specifically in Southeast Asia (e.g., Singapore and Malaysia) and the Middle East (e.g., Saudi Arabia, United Arab Emirates, Bahrain, Kuwait, and Qatar).[16] No study on the Vitamin D status in these nonresident Bangladeshi (NRB) patients with T2DM is currently available. Hence, this study investigated the Vitamin D levels in NRB participants with T2DM and compared them with that of patients in the country.

  Materials and Methods Top

This cross-sectional study was conducted at a specialized diabetes hospital in Cumilla city, Bangladesh, from July 2021 to February 2022. Bangladeshi patients with T2DM of both sexes attending the hospital's outpatient department for routine follow-up within the study period were included in the sample. Diabetes was diagnosed based on the American Diabetes Association criteria.[17] Patients diagnosed with DM at the age of ≥25 years with central obesity, acanthosis nigricans, and other features of insulin resistance without a history of ketoacidosis were categorized as T2DM. Those having a history of poor sunlight exposure, liver, kidney, or thyroid dysfunction, disorders of calcium metabolism, malignancy, recent severe acute illness, strict vegans, and those taking Vitamin D supplements were discarded. The study participants were divided into two categories, resident Bangladeshis (RB) and NRB. All participants provided written informed consent before inclusion. The study was conducted following the principles of biomedical research stated in the Declaration of Helsinki.

Assuming the prevalence of VDD of 30% in T2DM (according to a study by Alam et al.), 95% confidence level, and 5% error, the estimated sample size was 323.[11] Due to resource and budget limitations, the target sample size was 250 (125 in both groups). Data were collected using a predesigned semi-structured case record form. Relevant clinical history was taken, and physical examinations were conducted by the principal investigator. Sitting blood pressure (BP), standing height, and weight were measured following the standard procedures with validated instruments. Individuals on antihypertensive drugs or with BP ≥140/90 mmHg were considered hypertensive.[18] The body mass index (BMI) was calculated, and obesity was defined as BMI ≥25.0 kg/m2.[19] Lipid profile was measured in the fasting state using the Dimension® 122 EXL™ 200 Integrated Chemistry System (Siemens Healthcare Diagnostics Inc., Newark, DE 19714–6101, USA) using the spectrophotometric method. Dyslipidemia was defined according to the Adult Treatment Panel III guidelines.[20] Glycated hemoglobin (HbA1c) was measured using the Bio-Rad D-10® analyzer (Bio-Rad Laboratories, CA, USA) using ion exchange-high-performance liquid chromatography, and HbA1c <7.0% described a good glycemic control.[17] The serum 25-hydroxy (OH) vitamin D [25(OH)D] levels were measured with an electrochemiluminescent immunoassay (VITROS® 25-OH Vitamin D Total Assay) on an automated machine (VITROS ECi, Johnson and Johnson, Rochester, NY, USA). 25(OH) D levels were considered sufficient (≥30 ng/mL), insufficient (20–29.9 ng/mL), and deficient (<20 ng/mL) as per the Clinical Practice Guidelines (2011) of the Endocrine Society.[21]

Data were analyzed using the IBM SPSS Statistics for Macintosh, Version 28.0 (IBM Corp. Released 2021, Armonk, NY) software. The continuous variables with normal distribution and without a normal distribution were expressed as mean ± standard deviation and median (interquartile range, IQR), respectively. The categorical variables were presented as percentages (numbers). As applicable, the Student's t-test, the Chi-square test, and the Mann–Whitney U-test were applied to compare the variables between the two groups. A two-sided P < 0.05 indicated a statistical significance.

  Results Top

A total of 250 patients with T2DM were evaluated; 125 were RBs, and 125 were s NRBs. Sixteen patients in the RB group were omitted from the final analysis for the incompleteness of data. Hence, 109 RBs and 125 NRBs, a total of 234 patients, were considered for final analysis. Their mean age was 42.5 ± 9.4 years. 79.1% were obese, 45.7% were hypertensive, and 93.6% were dyslipidemic. DM was uncontrolled in 88.9%. Their mean 25(OH)D level was 25.7 ± 10.2 ng/mL; 30.3%, 38.5%, and 31.2% of the study participants were sufficient, insufficient, and deficient in Vitamin D, respectively. NRB group had no female participants. The frequencies of smokers and dyslipidemia were higher among RBs. BMI and HbA1c were higher, and low-density lipoprotein cholesterol (LDL-C) was lower among NRBs than RBs. RBs and NRBs had similar 25 (OH) D levels (25.7 ± 11.9 vs. 25.8 ± 8.5 ng/mL, P = 0.948) and VDD status (36.7% vs. 26.4%, P = 0.124) [Table 1].
Table 1: Characteristics of the study participants

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The Middle East countries were the residing countries of most of the NRBs [Figure 1]. Their mean duration of staying abroad was 14.5 ± 7.2 years.
Figure 1: Geographical areas of residence of the NRBs. NRBs: Nonresident Bangladeshis

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[Table 2] summarizes the serum 25(OH)D levels and Vitamin D status between different subgroups of the study participants. Participants in the age group of ≥50 years had higher 25(OH)D levels than those in the age group of <50 years. No differences were observed in 25(OH)D levels between males and females, nonsmokers and smokers, nonobese and obese, normotensives and hypertensives, patients with controlled and uncontrolled DM, and dyslipidemic and nondyslipidemic patients. The Vitamin D levels were similar across the mentioned subgroups.
Table 2: Serum 25(OH)D levels and status in different subgroups of the study participants

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Among the variables, the serum 25(OH)D levels positively correlated with only the age of the study participants (r = 0.137, P = 0.037) [Table 3].
Table 3: Correlations of serum 25(OH)D levels with other variables

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  Discussion Top

This study evaluating 109 RBs and 125 NRBs found no difference in the serum 25(OH)D levels between the two groups. Although 38.5% of the study participants had Vitamin D insufficiency and 31.2% had D deficiency, the frequencies of Vitamin D insufficiency and deficiency were similar RBs and NRBs. Most of the study participants had a poor glycemic control; NRBs had higher HbA1c than RBs.

VDD is highly prevalent in this area. In a meta-analysis of five studies from Bangladesh consisting of 695 otherwise healthy participants, the mean Vitamin D level was 16.14 (±4.83) ng/mL, and the prevalence of VDD (<20 ng/mL) was 67%.[10] A few studies also evaluated Vitamin D status in patients with T2DM in Bangladesh. Alam et al. reported the mean serum 25(OH)D level of 27.91 ± 2.58 ng/mL in newly diagnosed patients with T2DM. Among the study participants, 30% were D-deficient, and 36% were D-insufficient.[11] The serum 25(OH)D level in the newly diagnosed T2DM was 17.7 ± 4.5 ng/mL, as observed by Anwar et al.; 27.5% had VDD, according to the study.[12] Talukder et al. reported a 64.10% insufficiency and 20.51% deficiency of Vitamin D in their research.[13] Among the cases of T2DM, the mean Vitamin D was 11.01 ± 6.03 ng/mL, and 93.4% had Vitamin D <20 ng/mL, according to Hossain et al.[14] In this study, the mean 25(OH)D level was 25.7 ± 10.2 ng/mL, almost similar to Alam et al.'s study, but higher than the others. Differences in the studied population, Vitamin D assay method, and many other factors may explain such heterogenicity in the available study reports.

In this study, we observed similar 25(OH)D levels and frequencies of VDD among NRBs and RBs. Most of NRBs were residing in Middle East countries. The Tropic of Cancer also referred to as the Northern Tropic, is the most northerly circle of latitude on the Earth at which the Sun can be directly overhead. The circle is currently 23°26'10.7” (or 23.43631°) north of the quator. In Asia, the line crosses through Taiwan, China, Myanmar, Bangladesh, India, Oman, United Arab Emirates, and Saudi Arabia.[22] Many factors influence the photosynthesis and bioavailability of Vitamin D and contribute to the risk of low Vitamin D status. Besides the geographical location, these factors include variations in sun exposure due to latitude, season, time of day, atmospheric components, clothing, sunscreen use, and skin pigmentation, as well as age, obesity, and the incidence of several chronic illnesses.[8] In a study conducted in Saudi Arabia among patients with T2DM, the mean Vitamin D level was 13.51 ± 4.6, and 93.75% were Vitamin D deficient.[23] In another study in the same country, the mean serum 25OHD levels in the diabetic group were 15.7 ± 7.5 ng/mL, and 76.6% had VDD.[24] In T2DM, the other study in the country reported the mean of serum 25 (OH) Vitamin D of 20.27 ± 8.66 ng/mL and VDD of 63%.[25] Hence, despite sharing similar equatorial areas, patients from the Middle East countries with T2DM have lower Vitamin D levels than the patients from Bangladesh. Even NRBs in the current study had higher Vitamin D levels than the resident Middle East people in the previous reports. Genetic factors influencing Vitamin D metabolism, skin color, and many other physical and sociocultural factors are responsible for such variations in the Vitamin D levels among patients with T2DM from the Middle East and Bangladesh, even the NRBs living in the Middle East. Thus, it is obvious that factors other than geographical locations impact Vitamin D status. These factors may include genetic, physical, and sociocultural factors affecting Vitamin D metabolism, which is not lost even after staying abroad for more than a decade.

In this study, the serum 25(OH)D level was higher in the higher age group, and D levels positively correlated with the age of the participants, but not with other variables, including BMI, HbA1c, and lipid parameters. Previous studies in Bangladesh found no correlation between Vitamin D with age, but positive correlations between D levels negatively correlated glycemic status.[11],[12],[14]

The study has several limitations. Single-centeredness and small sample size limit its generalizability. The baseline Vitamin D status of the NRBs before going abroad was unavailable. Moreover, we did not search for the study participants' food habits, clothing patterns, the extent of sun exposure, duration of diabetes, and glucose-lowering drugs. This study's NRBs were all male, which is another limitation.

  Conclusion Top

Low Vitamin D is highly prevalent in resident and NRBs with T2DM though they have similar Vitamin D levels and comparable rates of VDD. Further studies with large sample sizes are needed to determine the factors influencing Vitamin D status in Bangladeshi patients with T2DM residing in different parts of the world.

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Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1]

  [Table 1], [Table 2], [Table 3]


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