Gender-related differences in the association of serum levels of vitamin D with body mass index in northern Iranian population: the PERSIAN Guilan Cohort Study (PGCS)

BACKGROUND: Vitamin D (VD) insufficiency has now become a global problem throughout the world. The association between increasing body mass index (BMI) and VD insufficiency has attracted great attention in recent researches. The aim was to study if BMI was independently associated with serum 25-hydroxy VD in a large population-based study, specify by gender. METHODS: Data on 9520 adults 35 years and older participating in PERSIAN Guilan Cohort Study (PGCS) were used. Serum levels of 25-hydroxy VD less than 20 ng/mL (50 nmol/L) was used as a measure of VD inadequacy. Multiple logistic and linear regression analyses were used to estimate the strength of the association between VD and BMI before and after adjusting for demographic factors and lifestyle variables. RESULTS: After adjustment in male population, overweight (adjusted OR = 1.2, P < 0.05) and obese (adjusted OR = 1.4, P > 0.05) individuals were more likely to have VD inadequacy than normal weight counterparts. Moreover, there was a weak inverse linear association between BMI and serum 25 (OH) D levels in males (β = -0.14, P value > 0.05). In contrast, no significant associations between BMI and serum 25 (OH (D levels were observed in females. In male population, higher BMI were associated with lower serum vitamin 25 (OH) D levels. CONCLUSIONS: However, association between BMI and VD level was not observed in female population. The suggestion of current study for public health was special consideration to serum VD levels in over weight and obese males.