Association between serum 25-hydroxyvitamin D level and insulin resistance in an elderly Korean population

Abstract

INTRODUCTION A low serum vitamin D concentration has been reported to be associated with increased risk of diabetes mellitus. But the relationship with 25-hydroxyvitamin D [25(OH)D] level and insulin resistance has not been ascertained in the Korean elderly population. The purpose of this study was to investigate the association between 25(OH)D level and insulin resistance in community-living elderly Koreans. METHODSThis study used data from the Korean Urban Rural Elderly (KURE) study. In 2011 study, 927 participants aged 65 years or older completed baseline health examinations. Participants were recruited from an urban and a rural community. After excluding two individuals missing 25(OH)D value, cross-sectional analyses were conducted for 925 participants (302 men and 623 women). Serum 25(OH)D was used as a continuous variable and categorized into three groups: <20, 20-<30, and ≥30 ng/ml. Plasma glucose and serum insulin levels were measured from overnight fasting blood samples and homeostasis model assessment for insulin resistance (HOMA-IR) was calculated using them. Fasting glucose, insulin, and HOMA-IR were log-transformed for parametric tests. RESULTSIn men, serum 25(OH)D level had a significant association with HOMA-IR (β=-0.015, p=0.006) in an age-adjusted model and a marginally significant association with HOMA-IR (β=-0.008, p=0.074) after additional adjusting for body mass index, waist circumference, smoking status, alcohol intake, and regular exercise. However, there were significant differences in serum 25(OH)D level (18.7 vs. 26.4 ng/ml; p<0.001) and HOMA-IR (1.6 vs. 1.0; p<0.001) between urban and rural areas. After additional adjusting for residential area, the association was not significant (β=-0.0003, p=0.955). In women, the association between 25(OH)D and HOMA-IR was not significant before (p=0.503) and after (p=0.855) adjustment for residential area.CONCLUSIONSIn men, serum 25(OH)D level was marginally significantly associated with HOMA-IR after adjustment for age, body mass index, waist circumference, smoking status, alcohol intake, and regular exercise, however, the association was not significant after additional adjusting for residential area. In women, the association between 25(OH)D and HOMA-IR was not significant before and after adjustment for residential area. Our findings suggest that vitamin D was not independently associated with insulin resistance in elderly Korean men and women dwelling in an urban and a rural.