Introduction
Vitamin D is a steroid hormone essential for bone and mineral homeostasis. The hormonally active form, 1,25-dihydroxyvitamin D3 [1,25(OH)₂D₃], regulates calcium metabolism, cellular growth, and proliferation. Serum 25-hydroxyvitamin D [25(OH)D] is the most reliable indicator of Vitamin D status. Vitamin D is critical for immune regulation and has anti-inflammatory and immunomodulatory properties that help in prevention of autoimmunity [1].
Vitamin D deficiency is highly prevalent in India, affecting approximately 70–90% of individuals across all age groups and genders [2]. The major contributing factors include reduced sunlight exposure due to lifestyle, cultural practices and lack of dietary Vitamin D fortification [3]. It has been hypothesized that Vitamin D deficiency may predispose to a higher risk of cardiovascular diseases, although the causal relationship remains to be fully elucidated [4].
Vitamin D plays a significant role in cardiovascular physiology and disease pathogenesis, including thrombosis, inflammation and regulation of the renin-angiotensin system. Its deficiency has been implicated in the development of degenerative cardiovascular disease and vascular calcification. Vitamin D deficiency is associated with several chronic conditions, including metabolic syndrome, hypertension, diabetes mellitus, coronary artery disease and heart failure [5][6].
Increased vascular stiffness and inflammation are recognized surrogates of atherosclerotic burden. Vitamin D is postulated to exert vasculoprotective effects by reducing inflammation and oxidative stress. Vitamin D deficiency is linked to endothelial dysfunction driven by inflammatory pathways [7].
Materials and Methods
Study design: A hospital based cross sectional study was conducted among 244 patients diagnosed with Hypovitaminosis D and admitted to the Medicine wards of Department of General Medicine, Nagaland Institute of Medical Sciences and Research (NIMSR), Kohima, Nagaland. The objective of the study was to assess the distribution of 25-hydroxyvitamin D (25-OH D) levels and its potential associations with demographic factors.
Study duration: The study was done over a period of 2 (two) year from June 2024 to May 2026.
Inclusion Criteria
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Age above 18 years
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Patients of both gender diagnosed with Hypovitaminosis D and admitted to the Medicine wards for various illness
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Those who gave consent to undergo the study
Exclusion Criteria
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Age less than 18 years
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Patients on steroids, anti-epileptics, thyroid disorders, malignancy, pregnancy. Etc
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Those on Vitamin D supplements
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Those not willing to take part in the study were excluded
Study tools
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A pre-defined proforma for collecting the socio-demographic, clinical and disease characteristics
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Serum Vitamin D 25-hydroxyvitamin D (25-OH D) levels measured by Immuno-enzyme Assay
Operational definitions: Vitamin D level were classified as Optimal (>30 ng/ml), Insufficiency (20–29 ng/ml) and Deficiency (<20 ng/ml).
Study procedure: The participants were informed about the nature of the study which was fully explained in the participant information sheet and only those who agreed to undergo the study signed in the informed consent form. Their participation was completely voluntary and right to deny to participate in the study was reserved. The anthropometric measurements of the participants were recorded. Body Mass Index (BMI) was calculated using Quetelet’s formula: BMI = weight (kg) / [height (m)]². Blood pressure of the participants was measured after a 5-minute rest period in the seated position. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were recorded using a standardized sphygmomanometer, following standard operating procedures and recommended precautions. The diagnostic criteria for hypertension was as per the ACC/AHA 2017 guidelines.
The blood samples were collected and analyzed in the central laboratory. Plasma 25-OH vitamin D was measured using Snibe Maglumi X3 Immunoassay Analyzer. Glucose, creatinine, AST, ALT, ALP, calcium, albumin, LDH, triglyceride, total cholesterol, HDL and LDL levels were measured using Transasia XL 640 auto analyser. Electrocardiogram was done using Clarity Med, model: ECG 100D-3Ch, manufactured in India. Echocardiography was done using SONOACE X8 Version 2.03.00. M345-E20300-00. Other miscellaneous test were done as and when required. Privacy and confidentiality was maintained at all cost for each participant. The data collected were documented and analysed statistically to draw a useful conclusion.
Statistical analyses: The collected data was analysed using SPSS (Statistical Package for Social Sciences software) 22.0, and R environment ver.3.2.2 were used for the analysis of the data and Microsoft word and Excel have been used to generate graphs, tables etc. Descriptive statistics like frequency, percentage, mean, standard deviation and proportions were used. A probability value < 0.05 was considered as statistically significant.
Results
| Characteristics | Frequency (%) |
| Age in years | |
| ≤20 | 12 (5) |
| 21 – 30 | 14 (6) |
| 31 – 40 | 38 (15) |
| 41 – 50 | 58 (24) |
| 51 – 60 | 52 (21) |
| 61 – 70 | 32 (13) |
| ≥71 | 38 (16) |
| Gender | |
| Male | 136 (56) |
| Female | 108 (44) |
| Education | |
| Illiterate | 30 (12) |
| Primary | 58 (24) |
| High school | 74 (30) |
| Higher secondary | 44 (18) |
| Degree/diploma | 38 (16) |
| Residence | |
| Rural | 88 (36) |
| Urban | 156 (64) |
| BMI category (kg/m²) | |
| 18.5–24.9 | 120 (49) |
| 25–29.9 | 92 (38) |
| ≥30 | 32 (13) |
| Comorbidity | |
| Hypertension | 160 (66) |
| Diabetes | 78 (32) |
| Dyslipidemia | 72 (30) |
| Chronic Kidney Disease | 40 (16) |
| Chronic Liver Disease | 74 (30) |
| Coronary Artery Disease | 32 (13) |
| Congestive Heart Failure | 20 (8) |
| Vitamin D level | |
| Optimal (>30 ng/ml) | 0 |
| Insufficiency (20–29 ng/ml) | 98 (40) |
| Deficiency (<20 ng/ml) | 146 (60) |
In our study, 244 patients with Hypovitaminosis D were assessed for the distribution of 25-hydroxyvitamin D (25-OH D) levels and its potential association with demographic factors. The baseline characteristics of the study population is listed in Table 1. The age of the study population ranged from 19 years to 84 years. The mean age of the study population was 50.8 ± 16.3 years. The most common age group of occurrence in the study was 41 to 50 years at 24%. In the gender distribution, males at 56% were predominant compared to female. In terms of educational status, 12% patients were illiterate and 30% completed high school studies. In the study population, 64% patients with Hypovitaminosis D were residents of urban areas and 49% patients had Body Mass Index (BMI) of 18.5–24.9 kg/m.²
In the study of comorbidities in 244 patients with Hypovitaminosis D, 66% patients had Hypertension. Serum Vitamin D 25-hydroxyvitamin D (25-OH D) levels measured by Immuno-enzyme Assay noted 60% patients with Vitamin D deficiency (<20 ng/ml) levels and 40% patients with insufficiency (20–29 ng/ml) levels in the study population (Table 1).
| Age in years | Frequency (%) | Deficiency (<20 ng/ml) | Insufficiency (20–29 ng/ml) |
| ≤20 | 12 (5) | 10 | 2 |
| 21 - 30 | 14 (6) | 12 | 2 |
| 31 – 40 | 38 (15) | 26 | 12 |
| 41 – 50 | 58 (24) | 30 | 28 |
| 51 – 60 | 52 (21) | 32 | 20 |
| 61 – 70 | 32 (13) | 14 | 18 |
| ≥70 | 38 (16) | 22 | 16 |
| Total | 244 | 146 | 98 |
The demographic distribution of 25-hydroxyvitamin D (25-OH D) levels in the study population is listed in Table 2. In the assessment of distribution of 25-hydroxyvitamin D (25-OH D) levels in association with demographic factors in the study population, Vitamin D deficiency at <20 ng/ml was highest in 51 – 60 years [n=32/52, 61.5%], while insufficiency at 20–29 ng/ml peaked in 41 – 50 years [n=28/58, 48.3%]. The high burden of Vitamin D deficiency and insufficiency highlights the need for population-level interventions (Table 2).
Discussion
Vitamin D undergoes 25-hydroxylation in the liver to form 25-hydroxyvitamin D [25(OH)D], the primary circulating metabolite. Vitamin D can be endogenously synthesized in the skin following ultraviolet B (UV-B) radiation exposure and does not necessarily require dietary intake. However, due to seasonal variations in ultraviolet B (UV-B) availability and reduced sun exposure related to practices and limited outdoor activity, the population has become increasingly dependent on dietary sources of Vitamin D [8].
In our study, 244 subjects were assessed for Vitamin D status and associated clinical correlates. The baseline characteristics provided important insight into the demographic and clinical profile predisposing to hypovitaminosis D in the study population. We observed 60% deficiency [<20 ng/ml] and 40% insufficiency [20-29 ng/ml] levels of Vitamin D in the study population. This alarming burden is consistent with data reported across regions in India despite abundant sunshine [9][10].
The majority of subjects belonged to 41-50 years [24%] age group. Vitamin D deficiency was highest in 51-60 years [n=32/52, 61.5%] age group, while insufficiency level peaked in 41-50 years [n=28/58, 48.3%] age group. The 41-50 years group showing peak insufficiency in our study represents a crucial transitional phase where insufficiency progresses to overt deficiency in the next decade if not supplemented. Advancing age is a well-established risk factor for Vitamin D deficiency due to reduced cutaneous synthesis of 7-dehydrocholesterol, reduced outdoor activity, increased adiposity with sequestration of Vitamin D and impaired renal 1-α hydroxylation [11][12]. Selvarajan S et al.,[13] and Harinarayan CV et al.,[14] in their study on Vitamin D level reported significantly lower 25-OH D levels beyond 50 years.
Notably in our study, younger age groups showed high deficiency: ≤20 years [10/12, 83.3%], 21-30 years [12/14, 85.7%] and 31-40 years [26/38, 68.4%] were deficient in levels of Vitamin D. Marwaha RK et al.,[15] and Zargar AH et al.,[16] in their study reported early-onset deficiency of Vitamin D attributed to indoor lifestyle, air pollution, extensive sunscreen use, traditional clothing and low intake of fortified foods.
We observed male preponderance at 56% [n=136] in our study, possibly reflecting higher hospital attendance for co-morbidities among males in our setting. Selvarajan et al.,[13] in their systematic review reported comparable prevalence across genders when adjusted for occupation and sunlight exposure.
Lower educational status is often associated with reduced awareness regarding dietary sources and health benefits of Vitamin D. Urban residence was predominant [64%, n=156] compared to rural [36%] in our study. This is consistent with the findings of Ritu G et al.,[10] and Harinarayan CV et al.,[14] with a reported higher prevalence of Vitamin D deficiency in urban population compared to rural, attributed to air pollution blocking ultraviolet B (UV-B) rays, indoor jobs and reduced sun exposure. Urbanization is a major driver of Vitamin D deficiency in India.
In our study, 51% subjects were overweight/obese [38% BMI 25-29.9 and 13% BMI ≥30]. Vitamin D, being fat-soluble, is sequestered in adipose tissue resulting in low bioavailability. Wortsman J et al.,[17] demonstrated lower rise in Vitamin D levels in obese subjects after ultraviolet B (UV-B) exposure compared to non-obese subjects.
Hypertension was the most common comorbidity [66%, n=160], followed by diabetes [32%], dyslipidemia [30%] and chronic liver disease [30%] in our study. This clustering is significant. Vitamin D regulates renin-angiotensin system, insulin secretion and inflammation. Pittas AG et al.,[18] and Scragg R et al.,[19] reported association of low Vitamin D with hypertension, insulin resistance and dyslipidemia. Similarly, our finding of coronary artery disease in 13% and congestive heart failure in 8% is in line with studies linking Vitamin D deficiency to cardiovascular risk [20].
Conclusion
The study noted a high prevalence of Hypovitaminosis D across all age groups, peaking in the 5th and 6th decades of life. The burden of Vitamin D deficiency and insufficiency highlights the need for population level interventions. Screening of high-risk groups, health education and provision of targeted supplementation in high-risk age groups should be integrated to reduce morbidity associated with Hypovitaminosis D.
Limitations: Single-centre study, hospital-based with a limited sample size. Seasonal variation, dietary pattern, sunlight exposure duration, occupation, clothing and Parathyroid hormone levels were not evaluated. No control group with sufficient Vitamin D levels was included.
Declarations
Ethical Approval
Taken from the Ethics Committee.
Acknowledgement
The authors are grateful to the patients who participated in the study.
Conflict of Interest
None declared
Funding
Nil
Data Availability
Data available from the corresponding author upon reasonable request.
Informed Consent Statement
Not Applicable
Authors’ Contributions
All authors contributed equally to this paper.