Objective: Sarcopenia and insulin resistance are common co-morbidities in the elderly and are known to be associated with vitamin D deficiency. However, no previous studies have investigated interactions between all three of these factors. We aimed to investigate the relationship between 25-hydroxyvitamin D concentration, sarcopenia, and insulin resistance in postmenopausal Korean women.
Methods: This study used data from the Korea National Health and Nutrition Examination Survey 2008-2011. Participants were 3744 postmenopausal Korean women. Sarcopenia was defined as appendicular skeletal muscle mass divided by body weight >1 standard deviation below the mean for women aged 20-40 years. The serum 25-hydroxyvitamin D and fasting insulin levels were measured, and insulin resistance was calculated using the formula: fasting plasma glucose (mg/dl) × fasting insulin (mIU/l)/405.
Results: We found a strong inverse association between 25-hydroxyvitamin D concentration and sarcopenia in postmenopausal Korean women (p = 0.0009). There was also a significant association between sarcopenia and insulin resistance, independent of vitamin D and obesity status (p < 0.0001). However, there was no significant association between 25-hydroxyvitamin D concentration and insulin resistance. In the subgroup analysis, insulin resistance was found to be determined by sarcopenic rather than vitamin D status.
Conclusions: Sarcopenia was associated with both insulin resistance and 25-hydroxyvitamin D concentration in postmenopausal Korean women, regardless of obesity status. However, 25-hydroxyvitamin D concentration was not associated with insulin resistance. Sarcopenia is therefore of greater clinical importance due to its close relationship with insulin resistance.
Keywords: HOMA-IR; Vitamin D; insulin resistance; postmenopausal; sarcopenia.