Association Between Vitamin D Status, Metabolic Syndrome, and Menopausal Type: A Comparative Observational Study in Women with Early and Physiological Menopause

Background: The adverse cardiometabolic outcomes that have been associated with early menopause include obesity, insulin resistance, and metabolic syndrome. Other studies have also linked metabolic dysfunction with vitamin D deficiency. However, the independent association of serum 25-hydroxyvitamin D [25(OH)D] concentrations with metabolic syndrome and type of menopause is unclear. Thus, the present study was designed to assess the association between vitamin D status and metabolic syndrome in women with early menopause compared with those with natural menopause. Methods: A total of 301 postmenopausal women were enrolled. Metabolic syndrome was assessed independently according to the NCEP-ATP III and IDF diagnostic definitions. They were classified into two groups: early menopause (EM, n = 79) and physiological menopause (PHYSM, n = 222). Demographic, anthropometric, biochemical, and lifestyle characteristics were recorded. The criteria for diagnosing metabolic syndrome were those of the National Cholesterol Education Program Adult Treatment Panel III (NCEP-ATP III) and the International Diabetes Federation (IDF). Serum 25(OH)D was also categorized as deficiency, insufficiency, or sufficiency. Multivariable logistic regression analyses were used to determine independent predictors of metabolic syndrome. Multivariable linear regression analyses were used to determine the association between serum 25(OH)D and individual metabolic parameters. Results: Women with early menopause had a higher body mass index than those with physiological menopause, whereas current smoking was more prevalent among women with physiological menopause. No significant differences were observed between the groups in the prevalence of metabolic syndrome, 25(OH)D concentrations, lipid profile, blood pressure, glycaemic indices, or other biochemical parameters. In multivariable analyses, menopausal status was not independently associated with metabolic syndrome according to either the NCEP-ATP III or IDF criteria. Body mass index was the only independent predictor of metabolic syndrome in the adjusted IDF model (OR 1.2, 95% CI 1.0–1.4; p = 0.047). Serum 25(OH)D concentrations were independently associated only with lower fasting glucose levels and were not independently associated with metabolic syndrome or its other components. Although vitamin D categories showed significant associations with metabolic syndrome in unadjusted analyses, these associations were attenuated after adjustment for demographic, anthropometric, menopausal, and lifestyle-related factors. Conclusions: Menopausal type was not independently associated with the prevalence of metabolic syndrome or vitamin D status. Although metabolic syndrome prevalence differed across vitamin D categories in unadjusted analyses, these associations were attenuated after adjustment for demographic, anthropometric, menopausal, and lifestyle-related factors. Obesity appeared to be the strongest independent predictor of metabolic syndrome within this cohort. Given the retrospective observational design, these findings should be interpreted cautiously, and prospective longitudinal studies are warranted to confirm these associations.