Evaluation of the relationship between lifestyle factors and vitamin D levels in healthcare workers

Authors

Abstract

AimThis study evaluated the effects of lifestyle habits on serum 25(OH)D levels and the prevalence of vitamin D deficiency among healthcare workers.
Methods In this retrospective study, laboratory and demographic data of 204 healthcare workers who attended the Internal Medicine outpatient clinic between January 1, 2023, and January 1, 2024, and had serum vitamin D levels measured were analyzed. Lifestyle factors, including sun exposure, clothing style, physical activity, smoking, and alcohol use, were assessed using a researcher-designed questionnaire. Categorical variables were expressed as frequencies and percentages, and continuous variables as means or medians according to data distribution. Statistical analyses were performed.
Results The mean serum 25(OH)D level was 7.31 ± 5.41 ng / mL, indicating marked vitamin D deficiency. Vitamin D levels were slightly higher in males than in females; however, the difference was not statistically significant (p > 0.05). Participants who dressed according to seasonal conditions and those with daily sun exposure exceeding 30 minutes had significantly higher vitamin D levels (p < 0.05). No significant associations were observed between vitamin D levels and profession, mode of transportation, or frequency of physical activity (p > 0.05).
Conclusion Vitamin D deficiency was highly prevalent among healthcare workers. Adequate sun exposure and clothing that allows skin exposure positively influenced serum vitamin D levels, highlighting the need for increased awareness and preventive strategies. Further multicenter prospective studies are needed to clarify the relationship between lifestyle factors and vitamin D status.

Keywords

Introduction

Vitamin D is a fat-soluble steroid prohormone that plays a critical role in regulating calcium-phosphorus metabolism and maintaining bone health. However, recent studies have shown that the functions of vitamin D are not limited to the skeletal system; it is also involved in numerous biological processes, including immune function, cardiovascular health, endocrine regulation, and cellular proliferation.^1,2
Vitamin D deficiency has been reported as a widespread public health issue globally. A recent meta-analysis in Europe reported the prevalence of serum 25(OH)D levels < 30 nmol / L as 15.7%, < 50 nmol / L as 47.9%, and < 75 nmol / L as 76.6%.³ Limited sun exposure, urban lifestyles, air pollution, prolonged indoor activity, and inadequate dietary habits are among the main contributing factors to this deficiency.^4,5 Vitamin D deficiency is associated with osteomalacia, osteoporosis, muscle weakness, and an increased risk of falls, as well as diabetes, cardiovascular diseases, infections, and autoimmune disorders.^6,7
Healthcare workers are considered a high-risk group for vitamin D deficiency due to occupational conditions. Shift work, prolonged time spent indoors, and heavy workloads have been reported to result in higher deficiency rates in this group compared to the general population.⁸ Villasis-Keever et al. (2024) analyzed factors affecting vitamin D levels in healthcare workers and demonstrated that lifestyle variables play a determining role.⁹ Similarly, Ito et al. (2024) reported a significant increase in vitamin D deficiency among healthcare personnel during the COVID-19 pandemic.¹⁰
However, studies comprehensively examining the relationship between lifestyle factors and vitamin D levels in healthcare workers remain limited. Therefore, this study aimed to analyze laboratory data from individuals attending the Internal Medicine outpatient clinic together with survey findings from healthcare workers to evaluate the relationship between lifestyle factors-including time spent outdoors, physical activity level, dietary habits, vitamin D supplementation, smoking, and alcohol consumption-and serum vitamin D levels. The findings of this evaluation are intended to contribute to the development of early intervention strategies for at-risk groups, increase awareness of vitamin D within preventive healthcare, and provide a scientific basis for population-level preventive policies.

Materials and Methods

This study retrospectively analyzed the relationship between lifestyle factors and serum vitamin D levels among healthcare workers and individuals attending the Internal Medicine outpatient clinic. Laboratory and demographic data were evaluated, and a questionnaire assessing past lifestyle habits was administered to healthcare workers.
Study Population and SampleThe study population consisted of individuals who visited the Internal Medicine outpatient clinic and had their serum vitamin D levels measured between January 1, 2023, and January 1, 2024. A total of 204 participants were included in the study. Healthcare workers were identified based on occupational information and were invited to complete the lifestyle questionnaire.
Data Collection and AnalysisBlood samples obtained during routine follow-up visits, as well as age and sex distributions, were recorded. The questionnaire included items related to sun exposure, dietary habits, physical activity, and smoking and alcohol use. Exclusion criteria included chronic liver disease, pregnancy, malignancy, acute infection, use of hepatotoxic drugs, and vitamin D supplementation.
Categorical variables were expressed as frequencies and percentages, and continuous variables were presented as medians. Skewness was calculated to assess data distribution. Non-normally distributed continuous variables were compared using the Mann-Whitney U test. The chi-square test or Pearson’s corrected chi-square test was used for categorical variables. Student’s t-test was applied for normally distributed continuous variables, while the Wilcoxon rank-sum test was used for non-normally distributed variables. Receiver operating characteristic (ROC) analysis was performed to evaluate the model’s ability to discriminate between positive and negative cases. All statistical analyses were performed using SPSS version 24.
Ethical ApprovalThis study was approved by the Ethics Committee of Harran University, Faculty of Medicine (Date: 2025-09-29, No: 251631).
Statistical AnalysisStatistical analyses were performed using SPSS version 24. Categorical variables were expressed as frequencies and percentages, while continuous variables were presented as medians (interquartile range). The normality of data distribution was assessed using skewness and appropriate normality tests.
For comparisons of continuous variables, the Mann-Whitney U test was used. Categorical variables were analyzed using the chi-square test or Fisher’s exact test, as appropriate. Receiver operating characteristic (ROC) analysis was performed to evaluate the model’s ability to discriminate between positive and negative cases.
Reporting GuidelinesThis study was reported in accordance with the STROBE guidelines.

Results

A total of 204 participants were included in the study. Of these, 63.7% were male (n = 130) and 36.3% were female (n = 74), with a median age of 42 years (range: 27-64 years).
When participants were analyzed according to profession, 26.5% were physicians (n = 54), 20.6% nurses (n = 42), 16.7% health technicians (n = 34), 13.7% secretaries (n = 28), 10.3% cleaning staff (n = 21), 6.9% administrative staff (n = 14), 4.9% other personnel (n = 10), and 0.5% hospital information management staff (n = 1).
The mean serum 25(OH)D level of the participants was 7.31 ± 5.41 ng / mL (range: 3.00-30.00 ng / mL). When analyzed by sex, males had slightly higher serum 25(OH)D levels than females, with mean levels of 7.46 ± 5.13 ng / mL in males and 7.02 ± 5.80 ng / mL in females; however, the difference was not statistically significant (p = 0.063).
Participants who dressed according to seasonal conditions had a mean serum 25(OH)D level of 7.64 ± 5.49 ng / mL, whereas those wearing clothing that fully covered the body had a mean level of 5.73 ± 4.60 ng / mL. Serum 25(OH)D levels were significantly higher in individuals dressing according to seasonal conditions compared with those covering their entire body (p = 0.009).
Participants with less than 30 minutes of daily sun exposure had a mean serum 25(OH)D level of 6.96 ± 5.14 ng / mL, whereas those with more than 30 minutes of sun exposure had a mean level of 8.71 ± 6.17 ng / mL. This difference was statistically significant (p = 0.044).
No significant differences in serum 25(OH)D were observed among professional groups, including physicians, nurses, technicians, secretaries, and cleaning staff (p = 0.29). Similarly, the mode of commuting to work (private vehicle or public transport) did not significantly affect serum 25(OH)D levels (p = 0.11). Although individuals engaging in regular physical activity once or three times per week tended to have higher mean serum 25(OH)D levels, this difference was not statistically significant (p = 0.19). The distribution of vitamin D levels according to demographic and lifestyle variables is presented in Table 1. Data regarding medication use, smoking, and alcohol consumption were insufficient for analysis and therefore, were not included in the study.

Discussion

This study evaluated the effects of lifestyle habits on serum 25(OH)D levels among healthcare workers. The findings revealed that participants had markedly low pre-treatment vitamin D levels, which significantly increased following intervention. These results are consistent with previous studies reporting a high prevalence of vitamin D deficiency among healthcare professionals.^11,12,13
Gender comparisons showed that male participants had slightly higher pre- and post-treatment vitamin D levels than females; however, this difference was not statistically significant. Previous literature also indicates that men often exhibit higher vitamin D levels compared to women.^14,15,16 This difference may be attributed to various biological and environmental factors, including differences in skin surface area, duration of sun exposure, and hormonal influences.¹⁷
Evaluation of clothing habits demonstrated that participants who dressed according to seasonal conditions and avoided fully covering garments had higher vitamin D levels. This finding aligns with existing literature emphasizing the critical role of sun exposure in vitamin D synthesis.^16,18 Additionally, participants exposed to sunlight for more than 30 minutes per day had significantly higher vitamin D levels, supporting the fundamental role of sun exposure in endogenous vitamin D production.^11,16,19
No significant differences in vitamin D levels were observed among professional groups. Similar levels among physicians, nurses, technicians, and other staff may be related to predominantly indoor working environments and comparable lifestyle characteristics.¹²
Furthermore, commuting methods, physical activity habits, and other lifestyle factors were not significantly associated with vitamin D levels. These findings suggest that vitamin D status is influenced by multiple interacting environmental, behavioral, and individual factors rather than a single lifestyle determinant.^14,15,20
Overall, the results underscore that vitamin D deficiency remains a significant public health concern among healthcare workers. Adequate sun exposure, seasonally appropriate clothing, and supplementation when necessary were found to positively influence vitamin D levels.

Limitations

The study was retrospective and limited to a single center. Lifestyle data relied on self-reported questionnaires, which may introduce recall bias.

Conclusion

This study highlights the high prevalence of vitamin D deficiency among healthcare professionals and emphasizes the importance of lifestyle factors, particularly sun exposure and clothing habits, in maintaining optimal vitamin D levels. Early recognition and intervention in at-risk populations, such as healthcare workers, can improve individual health outcomes and provide a foundation for preventive strategies at both institutional and community levels. Future multicenter and prospective studies are warranted to further investigate the interactions between lifestyle factors, vitamin D status, and their potential impacts on cardiometabolic health and immune function.

Declarations

Abbreviations

25(OH)D: 25-hydroxyvitamin D
COVID-19: Coronavirus disease 2019
ROC: Receiver operating characteristic
SPSS: Statistical Package for the Social Sciences
STROBE: Strengthening the Reporting of Observational Studies in Epidemiology

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About This Article

Received:

January 12, 2026

Accepted:

March 31, 2026

Published Online:

April 4, 2026