1.Effects of occupational sunlight exposure and monsoon season on vitamin D concentration among outdoor and indoor workers in Malaysia
Norliyana Aris ; Amal K. Mitra ; Wan Mohd Izani Bin Wan Mohamed ; Wan Abdul Manan Bin Wan Muda ; Hamid Jan Bin Jan Mohamed
Malaysian Journal of Nutrition 2020;26(No.3):425-439
Introduction: Despite abundant sunshine for cutaneous vitamin D synthesis, low
levels of vitamin D have been documented among the Malaysian population. The aim
of this study was to characterise the effects of occupational sunlight exposure and
monsoon season on serum 25-hydroxyvitamin D [25(OH)D] concentration. Methods:
A comparative cross-sectional study was performed among Malay outdoor (n=119)
and indoor workers (n=119) in Kelantan. Two-point data were collected on the same
participants, first during non-monsoon season and second during the northeast
monsoon season. Data collection comprised of anthropometry measurements (body
mass index and body fat), fasting blood test [serum 25(OH)D concentration], and
questionnaire (physical activity level, sun exposure, sun protection use, and vitamin
D intake). Vitamin D classification was based on the 2011 Endocrine Society Clinical
Practice Guidelines. Results: This study found that serum 25(OH)D concentrations
were significantly higher in outdoor compared to indoor workers irrespective of
season (p<0.001) and sex (p<0.001). Monsoonal differences in serum 25(OH)D
concentration was only observed in male outdoor workers (mean difference=10.39
nmol/l, p<0.001). Significant association between vitamin D status and occupation
was also observed (p<0.001). However, no significant association was found between
vitamin D status and monsoon season [χ2(1)=0.076, p=0.783]. Conclusion: Seasonal
and occupational factors should be considered while evaluating individual serum
25(OH)D concentration and in comparing community studies, especially among
workers.