Factors Associated with Vitamin D Deficiency Among Patients Referred for Vitamin D Testing in a Sri Lankan Tertiary Care Hospital: A Retrospective Analysis

Abstract

Background: Vitamin D deficiency (VDD) remains a common global health concern, including in tropical countries with abundant sunlight exposure. However, limited evidence exists regarding factors associated with VDD in Sri Lankan clinical populations. This study aimed to identify demographic, behavioural and clinical factors associated with VDD among patients referred for serum vitamin D testing at a tertiary care hospital in Sri Lanka.Methods: This retrospective hospital-based study included 427 patients who underwent serum 25-hydroxyvitamin D [25(OH)D] testing at the Colombo North Teaching Hospital, Ragama, between March 2021 and March 2022. VDD was defined as serum 25(OH)D levels <30 ng/mL according to Endocrine Society guidelines. Sociodemographic, lifestyle and clinical data were collected using interviewer-administered questionnaires. Multivariable binary logistic regression was performed to identify factors independently associated with VDD.Results: Among patients referred for vitamin D testing, 353 (82.7%) had VDD. In multivariable logistic regression analysis, increasing age was independently associated with lower odds of VDD (AOR 0.969 per year increase, 95% CI 0.948-0.990; p = 0.004). Female sex (AOR 2.210; 95% CI 1.167–4.186; p=0.015), and sun-protective behaviours (AOR 2.378; 95% CI 1.315–4.302; p=0.004) were independently associated with higher odds of VDD. Ethnicity, smoking status, medication use, chronic disease status and vitamin D–rich diet was not significantly associated with VDD.Conclusions: In this hospital-based cohort referred for vitamin D testing, younger age, female sex and sun protective behaviours were independently associated with VDD. These findings highlight the importance of behavioural and demographic factors influencing vitamin D status in clinically suspected populations in tropical settings.