Is a unified definition of metabolic syndrome needed? Comparison of three definitions of metabolic syndrome in 60-year-old men and women.

Background: There are three commonly used definitions of the metabolic syndrome, making scientific studies hard to compare. The aim of this study was to investigate agreement in the prevalence of the metabolic syndrome defined by three different definitions and to analyze definition and gender differences.

Methods: A population-based, cross-sectional study of a total of 4232 participants--2039 men and 2193 women, aged 60 years--was employed. Three different metabolic syndrome definitions were compared: European Group for the Study of Insulin Resistance (EGIR), International Diabetes Federation (IDF), and National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP III). Medical history, socioeconomic information, and lifestyle data were collected by a questionnaire. A medical examination including laboratory tests was performed. Significant factors for the metabolic syndrome were calculated by multivariate logistic regression.

Results: Forty five percent of men and 30% of women met the criteria for the metabolic syndrome by any definition, but only 17% of men and 9% of women met the criteria of all three definitions. The highest agreement was found between IDF and NCEP ATP III definition. Two significant associations were identified in both men and women by the three metabolic syndrome definitions; former smokers were highly associated with the metabolic syndrome (odds ratio [OR] congruent with 1.5), and regular physical activity (OR congruent with 0.6) was inversely associated with the metabolic syndrome.

Conclusions: Depending on the definition used, different individuals were identified as having the metabolic syndrome, which affects the reliability of interpretations to be made from scientific studies of the metabolic syndrome. Unified criteria are warranted. Physicians facing a physically inactive former smoker may consider diagnosing metabolic syndrome.