Metabolic Syndrome: Criteria Validation in the Elderly

The metabolic syndrome (MetS) is the term used to describe a clustering of metabolic and physiologic risk factors for both type 2 diabetes mellitus and atherosclerotic cardiovascular diseases first described about 40 years ago [1]. Despite an increasing number of works in the literature dedicated to MetS, its underlying mechanism is still not completely understood. Many studies have shown that four of its components – obesity (especially central obesity), impaired glucose tolerance, atherogenic dyslipidemia (high levels of triglycerides; small, dense low-density lipoproteins; and low levels of high density lipoprotein cholesterol), and hypertension ─ coexist in the population to a greater degree than could be expected by chance alone [2]. The first issue that needs to be addressed with regards to MetS is that the prevalence rates and the interactions between these components are probably different across sexes, age, and ethnic groups. Moreover, the definition of MetS is itself unclear, as its components are continuous variables, implying that cut-off values are needed. As yet there is no consensus as to the specific threshold to be used for each component [3]. Very few studies have, moreover, specifically focused on the validity of these criteria in the elderly (age > 65 yrs). In 2001, the National Cholesterol Education Program Third Adult Treatment Panel III (ATP III) proposed a series of criteria similar to those of the WHO [4], except for the fact that the key component was visceral obesity and not insulin resistance. The ATP III did not find enough evidence to recommend the routine measurement of insulin sensitivity or the 2-hour postchallenge glucose test but simply included a fasting glucose assessment. The ATP III criteria have recently been further revised [5] and the new definition recommends that at least 3 of the following 5 elements should be present: increased waist circumference (≥ 102 cm in men and ≥ 88 cm in women), hypertriglyceridemia (≥ 150 mg/dl or on drug treatment), low HDL cholesterol (< 40 mg/dl in men and < 50 mg/dl in women or on drug treatment), hypertension (≥ 130 mmHg systolic and ≥ 85 mmHg diastolic or on drug treatment), and a fasting glucose ≥ 100 mg/dL or on drug treatment. However, as the NCEP – ATP III criteria and cut-off values represent experts’ consensus and not evidence-based findings, their validity in different age groups needs to be verified.