Smoking and serum vitamin D in older Chinese people: Guangzhou Biobank Cohort Study

Jiang, Chao Qiang

INTRODUCTION: Studies regarding serum vitamin D in smokers showed conflicting results. Several studies reported lower serum 25-hydroxyvitamin D concentrations in smokers, while others found no significant differences or higher vitamin D in smokers. We examined the association of smoking status with serum vitamin D in older Chinese men, taking advantage of a community-based sample with natural exposure of vitamin D, because taking vitamin D supplements is rare in our setting.

METHODS: Multivariable logistic regression was used to assess the association of smoking status, including amount of cigarettes per day, duration of smoking and pack-years, with serum vitamin D (nmol/l) on 613 male participants aged 50+ years randomly selected from the Guangzhou Biobank Cohort Study from 2010 to 2011. Serum vitamin D was analysed using Enzyme immunoassay by Uranus (AE 90) Auto Analyzer.

RESULTS: The age adjusted mean (95% confidence interval) of serum vitamin D concentration was 57.7 (55.7-59.7), 57.3 (54.8-59.9) and 55.2 (52.9-57.4 ) nmol/l for never, former and current smokers, respectively. Adjusted for age, education, physical activity and high-density lipoprotein cholesterol, serum vitamin D concentrations decreased from never to former, then to current smokersadd adjusted mean for the 3 groups (P for trend 0.02). Compared to never smokers, current smokers had lower serum concentrations of vitamin D, and the concentrations decreased with the increasing number of cigarettes per day (from 1-19 to ≥20 cigarettes per day; adjusted P for trend 0.06), duration of smoking (from 1-39 to ≥40 years; adjusted P for trend 0.04) as well as pack-years (from 1-29 to ≥30 pack-years; adjusted P for trend 0.04).

CONCLUSIONS: Current smoking had lower serum concentrations of vitamin D than never smoker, and the associations were in a dose-response pattern, with higher amount of cigarettes per day, longer smoking duration and more pack-years being associated with lower vitamin D.