Vitamin D level and its association with adiposity among multi ethnic teachers in Wilayah Persekutuan Kuala Lumpur, Malaysia / Intan Shafinaz Sharifudin

Abstract

Vitamin D plays an essential role in health. Its deficiency can not only increase the 
 risk of osteoporosis, but also contribute to cardiovascular diseases, diabetes and certain 
 types of cancers. Skin synthesis of vitamin D from sunlight exposure constitutes the 
 major source of vitamin D. Evidences showed that not only temperate countries 
 experience the problem of vitamin D deficiency, but a similar problem exists in tropical 
 countries like Malaysia, Indonesia, Saudi Arabia and Tehran. Currently, there are new 
 evidences that show obesity may contribute to vitamin D deficiency. Obesity-associated 
 vitamin D deficiency is most likely due to the decreased bioavailability of vitamin D3 
 because of its deposition in the body fat compartments. 
 The aim of this study was to identify the risk factors contributing to a low serum 
 25(OH)D level and its association with adiposity among secondary school teachers in 
 the state of Wilayah Persekutuan Kuala Lumpur (WPKL). This was a cross sectional 
 study of two-stage sampling conducted from February 2013 to May 2013. First, 50% 
 out of a total of 80 government day schools in WPKL were randomly selected from 
 each district in Pudu, Bangsar, Sentul and Keramat respectively. Then, all teachers from 
 the selected schools who fulfilled the inclusion criteria of the study were invited to 
 participate. Ethics clearance was obtained from the University Malaya Medical Centre 
 (UMMC) Ethics Committee (Reference Number: 950.1). Approval from the Ministry of 
 Education, Education Board of Wilayah Persekutuan Kuala Lumpur (WPKL) and 
 principals from each selected schools were obtained before data collection. Informed 
 consent was obtained from all participants. The data collection included serum 25
 hydroxyvitamin D (25(OH)D), Parathyroid Hormone (PTH), blood glucose, fat 
 percentage, waist circumference and Body Mass Index (BMI). Demographic 
 iii 
 characteristics, sun exposure and avoidance, and level of physical activity were also 
 collected using a self-administered questionnaire. 
 A total of 858 participants were recruited. The majority of them were Malays, 
 females and married. The overall prevalence of vitamin D deficiency (<20 ng/ml) was 
 67.4%. Indian (80.9%) participants had the highest proportion of vitamin D deficiency, 
 followed by Malays (75.6%), others (44.9%) and Chinese (25.1%). There was a 
 significant negative association between serum 25(OH)D level with BMI (β= -0.23) and 
 body fat percentage (β= -0.14). In the multivariate linear regression analysis; Malays, 
 Indians, females (p<0.001), higher BMI and larger waist circumference (p<0.05) were 
 significantly associated with lower serum 25(OH)D level. The full model explained 
 32.8% of variation contributing to serum 25(OH)D level among the participants. 
 Adiposity explained only less than 1% of the variability of serum 25(OH)D level. The 
 two most influential factors affecting serum 25(OH)D level were ethnicity and sex. 
 Health education should be targeted in weight management, sex based behaviors on sun 
 exposure and avoidance, as skin pigmentation is non-modifiable.