[Local Data] Factors influencing vitamin D status in the Hong Kong population

• Background:
  • Participants included in this study were part of a household-based prospective study on influenza (from September 2009 to December 2010)
    • Influenza study: to study the direct and indirect effectiveness of influenza vaccination among school-age children in preventing influenza virus infection in their household
  • Objectives
    • To estimate age-specific and sex-specific serum 25-hydroxyvitamin D (25(OH)D) status in Hong Kong
    • To identify the determinants of serum 25(OH)D status
       
• Method:
  • All members of 796 households (2,694 subjects in total) were recruited, categorized into four groups: 6 - 17, 18 - 44, 45 - 64 and ≥ 65 years old
  • Each household included a child aged 6 - 17 years:
    • Randomly assigned to either single dose seasonal trivalent inactivated influenza vaccine group or placebo group in a double-blind setting
    • Serum specimens were collected at baseline and after 12 months
    • Serum specimens were also collected at 1 month after vaccination. Blood samples were provided by a subset of participants half-way through the study
    • Vitamin D questionnaire was used to collect data about sun-seeking behaviors, dietary and vitamin D supplementary habits from children aged 6 - 17 years in the group, mid-study serum specimens were also collected
  • Blood sample from all household members were collected for analysis
     
• Key Findings:
  • Mean values of serum 25(OH)D in different seasons

    Age group	n	2009 Autumn (Sep - Nov)	2009-10 Winter (Dec - Feb)	2010 Spring (Mar - May)	2010 Autumn (Sep - Nov)
    6 - 17 years	893	47 nmol/l	42 nmol/l	39 nmol/l	53 nmol/l
    18 - 44 years	800	53 nmol/l	48 nmol/l	42 nmol/l	57 nmol/l
    45 - 64 years	458	58 nmol/l	53 nmol/l	47 nmol/l	63 nmol/l
    65 years or older	42	56 nmol/l	51 nmol/l	41 nmol/l	54 nmol/l
    Sex
    Male	1,007	54 nmol/l	47 nmol/l	43 nmol/l	58 nmol/l
    Female	1,187	49 nmol/l	44 nmol/l	40 nmol/l	54 nmol/l

    *Serum 25(OH)D data in the summer were not available since no blood specimens were collected during Jun - Aug.
     

  • Children aged 6 - 17 years had significantly lower serum 25(OH)D levels compared to adults aged 18 - 44 years (p < 0.001) in each season
  • Adults aged 45 - 64 years had significantly higher serum 25(OH)D levels than adults aged 18 - 44 years on all seasons except winter of 2009 - 2010 (p < 0.01) in each season
  • Serum 25(OH)D levels in adults aged 65 or older were not significantly different from adults aged 18 - 44 years in each season
  • Males had significantly higher serum 25(OH) levels than females in each season
  • Five factors associated with higher serum 25(OH)D levels among children aged 6 - 17:
    • Younger age, male sex, reporting a suntan, consume at least 1 serving of fish and egg per week
       
• Conclusion:
  • Seasonal variation in serum 25(OH)D in Hong Kong:
    • Peaked in early autumn (September) dropped to lowest in early spring (March)
  • Adequate sunlight exposure is essential and increased fish and egg consumption can help to improve vitamin D status, especially for children and females during winter and spring

Link to PubMed

Reference

Xu C, Perera RA, Chan YH, Fang VJ, Ng S, Ip DK, Kam AM, Leung GM, Peiris JS, Cowling BJ. Determinants of serum 25-hydroxyvitamin D in Hong Kong. British Journal of Nutrition. 2015 Jun 8: 1-8. Epub ahead of print.

WYE-EM-233-JUL-15