Natl. J. Physiol. Pharm. Pharmacol.(2025), Vol. 15(5): 281-286

Research Article

10.5455/NJPPP.2025.v15.i5.2

Exploring vitamin D deficiency: A retrospective study of serum vitamin D levels in a Tertiary Hospital in Kerala

Sam Emmanuel Sabu¹, Tereesa Shojan^2* and Biju Bahuleyan²

¹Department of Endocrinology, Jubilee Mission Medical College and Research Institute, Thrissur, India

²Department of Physiology, Jubilee Mission Medical College and Research Institute, Thrissur, India

*Corresponding Author: Tereesa Shojan. Department of Physiology, Jubilee Mission Medical College and Research Institute, Thrissur, India. Email: shojantereesa [at] gmail.com

Submitted: 3/2/2025 Accepted: 14/4/2025 Published: XX/XX/XX

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ABSTRACT

Background: Vitamin D deficiency has emerged as a global health concern all over the world, with evidence linking low vitamin D levels to a diverse list of skeletal and non-skeletal disorders. This retrospective study aims to explore the serum vitamin D levels in patients attending a tertiary care hospital in Kerala and identify potential demographic factors contributing to this condition.

Aim: To assess the Vitamin D levels among patients admitted to a tertiary care hospital in Kerala in the past 3 years. To determine the associations between Vitamin D levels and demographic factors, such as age and gender.

Methods: A retrospective analysis was conducted using laboratory data from June 2021 to May 2024, collected from the AOSTA application, focusing primarily on Vitamin D levels, age, and gender of all patients over 18.

Results: From the laboratory data of 1940 study participants, 31.4% were deficient and 29.1% were insufficient in vitamin D. A total of 34.8% of the females were found to be deficient in comparison to males to a statistically significant level. Considering the age factor, Vitamin D deficiency was more prominent among younger age groups and this was statistically significant among females.

Conclusion: Despite Kerala’s tropical climate and ample sun exposure, Vitamin D deficiency remains surprisingly prevalent. The findings of this study also clearly show that targeted public health strategies in the form of screening, supplementation, and fortification should be implemented from an early age.

Keywords: Vitamin D deficiency, Demographic factors, Kerala.

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Introduction

Vitamin D is a fat-soluble vitamin that plays an important role in maintaining bone health, immune function, and cellular growth. The multiple roles of vitamin D in the body are explained by the fact that a wide variety of cells in the body have a vitamin D receptor (Rana et al., 2023). Vitamin D deficiency has now emerged as a health concern throughout the world, with evidence associating low levels of vitamin D to a variety of skeletal and non-skeletal disorders. Skeletal disorders include disorders such as rickets, osteoporosis, and fractures. Low vitamin D levels are also associated with certain non-skeletal disorders, including kidney diseases, diabetes mellitus, cardiovascular diseases, multiple sclerosis, autoimmune diseases, Crohn’s disease, depression, Alzheimer’s disease, obesity, cancer, and COPD (Mustafa and Shekhar, 2023). In India, there is an upcoming surge in vitamin D deficiency, which is said to be due to factors such as reduced duration of sun exposure, dietary factors, and lifestyle (Goel, 2020). The state of Kerala presents a unique case due to its tropical climate and high population density (Vijayakumar et al., 2020). Despite ample sunlight, the incidence of vitamin D deficiency remains a concern, especially in urban areas with reduced outdoor activity and dietary imbalances (Roy et al., 2024).

This retrospective study aims to explore the serum Vitamin D levels in patients attending a tertiary care hospital in Kerala and identify potential demographic factors contributing to this condition.

Objectives

To assess the Vitamin D levels among patients admitted to a tertiary care hospital in Kerala in the past 3 years.

To determine the associations between Vitamin D levels and demographic factors, such as age and sex.

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Materials and Methods

A total of 1940 subjects who had been tested for their vitamin D levels in the JMMC&RI laboratory in the past 3 years were included in this retrospective study conducted in the Department of Physiology, Jubilee Mission Medical College and Research Institute, Thrissur.

Sample size

The sample size was calculated to be 462. We included all the subjects tested for their vitamin D levels in our laboratory in the past 3 years and satisfied our inclusion criteria, which was 1940 subjects.

Guidelines by the US Endocrine Society-2011 were used here

It classifies Vitamin D status as deficiency below 20 ng/ml, insufficiency between 21 and 29 ng/ml, and sufficiency between 30 and 100 ng/ml (Selvarajan et al., 2017). This guideline was revised in June 2024, and we still used the old one in our study, as that is what is being followed in many hospitals, including ours even now.

Inclusion criteria

All patients who were 18 years of age or older and visited JMMC &RI and were tested for vit D in our laboratory within the past 3 years (June 2021 to May 2024) were included in the study.

Exclusion criteria

Records with incomplete data were excluded.

Sampling procedure

Convenience sampling

After receiving approval from the ethics committee, permission was obtained from the JMMC & RI laboratory to collect data from the electronic health record system of JMMC &RI (using AOSTA application). Serum 25-hydroxyvitamin D [25(OH)D] levels were measured using the VITROS 5600 Integrated System, which employs a chemiluminescent immunoassay for quantitative determination of total 25(OH)D in human serum.

This assay is standardized against recognized reference methods to ensure traceability and accuracy in vitamin D measurement. The VITROS 5600 system is designed to run clinical chemistry and immunoassay testing with a throughput of more than 900 tests per hour, depending on the test mix and sample workflow. Data regarding the age, sex, and vitamin D levels of all patients (18 years and above) who were tested in the past 3 years were collected and entered in the Excel sheet. The data were anonymized and stored in compliance with data protection regulations. To assess vitamin D levels, we used the guidelines of the US Endocrine Society (2011).

Descriptive data were categorized and presented as frequency and percentage. The chi-squared and t-tests were used for analysis. A p value of less than 0.05 was considered statistically significant.

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Results

Table 1: Gives the mean level of vitamin D among our population, minimum and maximum vitamin D values obtained.

Figure 1: Gender-wise distribution of subjects among each age group. There were more participants in the older age groups (>60, 46–60). There were more women than men in each age group. The youngest age group (18–25) had the least number of participants.

Table 2: Gives the distribution of study subjects with vitamin D deficiency, insufficiency, and sufficiency. A total of 31.4 of our study population had vitamin D deficiency and 29.1% had vitamin D Insufficiency. The mean values among these groups are also shown. The percentage of the study population who had vitamin D deficiency was 60.5%, which was very high.

Table 3: Association of gender with Vitamin D levels. Females had more vitamin D deficiency compared to males and this difference was statistically significant. 23.5% males and 34.8% females were. Insufficiency was slightly higher in males than in females, although the difference was not statistically significant.

Table 4: Shows Association between age groups and vitamin D levels gender wise. Even though males showed no significant association with varying age groups, females showed significant association and younger age groups had more vitamin D deficiency compared to older ones. 40.9% of females who belonged to the category of 18–25 years were vitamin D deficient. In addition, females in the menopausal age group (46–60 years) have more vitamin D deficiency than males of the same age group. It also shows the mean values.

Table 5: Shows that there is no significant correlation (Considering r Value) between age and vitamin D levels when the entire population is considered.

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Discussion

In this retrospective study conducted in the Department of Physiology, Jubilee Mission Medical College & Research Institute, Thrissur, we included a total of 1940 subjects who had been tested for their vitamin D levels in the JMMC&RI laboratory in the past 3 years.

The mean vitamin D levels among the study population was 29.68 (Table 1), which comes in the insufficiency range, this gives an overall idea about the vitamin D levels among the entire population. Also, the minimum and maximum values of vitamin D levels show that there were huge differences in vitamin D levels among our population. While analyzing the descriptive statistics it is better to group the study population age wise. Male and female population among each age group is also shown in Figure 1. Most of the study subjects (603 of them) were over 60 years old. The age group of 18–25 years had the minimum number of study participants.

Table 1. Descriptive statistics of vitamin levels of 1950 of our subjects.

Fig. 1. Gender wise distribution of subjects among each age group.

As per the US Endocrine Society guidelines (2011), the study subjects were classified into 3 groups, 31.4% of subjects had vitamin D deficiency, 29.1% of subjects had vitamin D insufficiency, and 39.5% of subjects had sufficient levels of vitamin D in their body (Table 2). This tells us that 60.5% of study subjects had vitamin D levels below 30ng/ml. It is also important to note that the mean vitamin D level among the deficient group was only 13.9± 4.2 which is too low. In the sufficient group, vitamin D levels average to 45.9 ± 17 which is closer to the lower limit. Vitamin D deficiency has recently been identified as a health hazard that is common in metropolitan cities around the world and India (Goel, 2020). A “Systematic Review on Vitamin D Level in Apparently Healthy Indian Population and Analysis of Its Associated Factors” conducted by Sandhiya Selvarajan, Vikneswaran Gunaseelan, and Nishanthi Anandabaskar et al. also showed an increased prevalence of Vitamin D deficiency. Decreased synthesis of Vitamin D in the body due to dark skin, limited outdoor activities due to our typically hot climate, abundance of clothes as part of the climate and culture, air conditioning, and the widespread use of sunscreens were all identified as factors for increased deficiency/insufficiency levels among our population (Selvarajan et al., 2017). All these factors could have contributed to the high vitamin D deficiency levels among our population as well. A study done by Praveen, Pradeep A, Singh et al, titled “Prevalence and Correlates of Vitamin D Deficiency among Adult Population in Urban and Rural Areas of the National Capital Region of Delhi, India” published in WHO South-East Asia Journal of Public Health (2023) has found severe vitamin D deficiency among 71% of the urban and 20% of rural population (Roy et al., 2024). The majority of the population attending our hospital also belongs to the urban category, which could have contributed to the high deficiency levels.

Table 2. Distribution of study subjects with vitamin D deficiency, insufficiency, and sufficiency.

Table 3. Association of gender with vitamin D levels.

Table 4. Association between age groups and vitamin D levels gender wise. Descriptive statistics.

Table 5. Correlation between age and vitamin D.

Table 3 shows vitamin D levels among males and females and it was observed that females were more susceptible to vitamin D deficiency than males (Ciarambino et al., 2023). There was a total of 586 males and 1,354 females included in the study. Multiple studies show that gender is one of the most important factors linked to Vitamin D deficiency, and females are more prone to vitamin D deficiency than males (Mustafa and Shekhar, 2023). In an article titled “Factors Associated with Vitamin D Deficiency and Their Relative Importance among Indian Adolescents: An Application of Dominance Analysis” published in the journal International Journal of Endocrinology they came to the conclusion that gender is the most important factor associated with vitamin D deficiency (Mustafa and Shekhar, 2023). Reasons for this could be due to the increased requirement of Vitamin D in females. During their life, women undergo various sexual and hormonal changes in their bodies including menarche, pregnancies, breastfeeding, use of contraceptives, and finally menopause (Ciarambino, 2023). The differences in vitamin D levels among males and females could also be due to variations in their lifestyle and behaviors. Males generally spend more time outside for occupational and recreational activities compared to females, which may be one reason for their higher serum Vitamin D concentration (Mustafa and Shekhar, 2023). Inadequate nourishment, multiparity, fully covered clothing, lack of education, and vulnerability in society are all problems faced by women in India and can be the reason for their higher vitamin D deficiency levels (Khadilkar, 2013).

One of the most striking observations in our study was the higher prevalence among younger individuals compared with the elderly, as shown in Table 4. This trend was observed in both males and females; however, the association was statistically significant among females (p-value < 0.001). Adolescents in urban areas, particularly females, demonstrated a greater likelihood of vitamin D deficiency compared to their rural counterparts (Rana et al., 2023). Several factors could contribute to this disparity, including sun avoidance behaviors to prevent tanning, lack of awareness regarding the need for supplementation, excessive sunscreen usage, and dietary inadequacies (Mustafa and Shekhar, 2023). Most of the subjects in the youngest age group are college students who will most likely be indoors attending classes during daylight hours (Tangpricha et al., 2002). Additionally, children and young adults are increasingly engaged in digital entertainment, leading to a sedentary lifestyle with limited outdoor activity, further reducing their exposure to natural sunlight and exacerbating vitamin D insufficiency (Sinha et al., 2022). To get an overall idea, we correlated age with vitamin D levels, without separating gender wise (Table 5), and it was noted that considering the r value, there was not much significance. This again shows that an age-wise association with vitamin D levels is more evident in females than in males.

It is important to note that most studies on vitamin D deficiency conducted in India relied on the 2011 US Endocrine Society guidelines. However, the applicability of these thresholds to the Indian population remains uncertain, as factors such as age, gender, ethnicity, duration of sun exposure, skin pigmentation, season, latitude, and certain health conditions, as well as factors like body weight, may influence baseline vitamin D levels (Selvarajan et al., 2017). This discrepancy could partly explain the high reported prevalence of vitamin D deficiency and insufficiency in various Indian studies. Establishing population-specific reference ranges is essential for accurately assessing and guiding clinical decisions.

In June 2024, the US Endocrine Society revised the 2011 guidelines. The new US Endocrine Society guidelines 2024, suggest supplements for those aged 1–18 years, adults over 75 years, pregnant people, and those with high-risk prediabetes. Because of the limited intake of natural food sources rich in vitamin D, empiric supplementation can be achieved through a combination of fortified foods and supplements that contain vitamin D. It also suggests against routine testing or empiric supplementation among those from 18–74 years of age. This is primarily because there is no data to show that a certain level is optimal for disease prevention. For patients who are symptomatic, testing is recommended, and if required, supplementations can be started (RDI-600IU daily).

Limitations of this study

Since this study was conducted exclusively within a hospital setting, the results may not accurately reflect the vitamin D status of the broader population in Kerala. Hospital-based data, which includes both in-patients and outpatients, often capture individuals who are already seeking medical care, potentially introducing selection bias, and we do not have information regarding the vitamin D supplementation status of the participants. Therefore, caution is necessary when generalizing these findings to the general population. However, this study serves as a pilot for a more comprehensive, population-based investigation that we plan to undertake in the future, which will provide a more representative assessment of vitamin D levels.

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Conclusion

While a significant number of individuals exhibit vitamin D deficiency, the true burden of the condition is likely much higher, as clinically diagnosed cases represent only the tip of the iceberg. In our study, we observed a large number of subjects with vitamin D deficiency, of which the majority belonged to the age group of 18–25 years. Among youngsters over the past years, there has been a rising trend toward musculo skeletal disorders and depression (Głąbska et al., 2021). This highlights the urgent need for targeted public health interventions to effectively address this widespread issue.

Key recommendations

• Educational programs:

Public awareness campaigns should be implemented to educate people about the importance of vitamin D, its role in overall health, and the risks of vitamin D deficiency. These initiatives should target diverse groups, including school children, pregnant women, youngsters, and the elderly. This can be achieved through health camps, workshops, and digital media. Additionally, healthcare professionals should be trained to recognize and address vitamin D deficiency proactively in clinical practice.

• Food fortification:

Given the dietary limitations and sun exposure patterns in many regions, mandatory food fortification with vitamin D is an effective strategy. Staples such as milk, flour, and cooking oils can be fortified to ensure adequate intake, particularly in populations that have limited sun exposure due to occupational or cultural practices. Successful models from other countries, such as the United States and Canada, can serve as frameworks for implementing similar programs in India.

• Supplement accessibility:

Ensuring that vitamin D supplements are both widely available and affordable is crucial, especially for vulnerable groups such as infants, pregnant women, elderly individuals, and those with chronic illnesses. Government-led initiatives can help subsidize supplements, integrate them into maternal and child health programs, and promote prescription-based supplementation for individuals at high risk of deficiency.

• Updated diagnostic guidelines:

Many hospitals in India still follow the outdated 2011 US Endocrine Society guidelines for vitamin D classification, despite evolving research and updated global recommendations. Given the current statistics, there is a pressing need to develop region-specific diagnostic criteria that better reflect local variations in vitamin D levels and associated health risks. The updated 2024 recommendations do not define specific target levels for 25(OH)D, shifting the focus from routine screening to targeted supplementation. This change reflects the current lack of conclusive evidence supporting an optimal vitamin D level for disease prevention.

• Further research:

More large-scale, population-based studies are needed to establish reference ranges for vitamin D levels among different demographic groups across India. We can employ the big data analytics method or indirect reference interval method to identify cut-off levels among our population. Research should also focus on understanding the impact of vitamin D deficiency on various health conditions, evaluating the effectiveness of supplementation and fortification programs, and identifying optimal sun exposure recommendations for different geographic regions.By implementing these strategies, policymakers and healthcare professionals can work toward reducing the prevalence of vitamin D deficiency and improving overall public health outcomes.

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