What is Metabolic Syndrome
Metabolic syndrome is a cluster of at least 3 out of 5 specific metabolic abnormalities—central obesity, elevated triglycerides, low HDL cholesterol, elevated blood pressure, and elevated fasting glucose—that together dramatically increase your risk of cardiovascular disease and type 2 diabetes. 1
Definition and Core Components
Metabolic syndrome represents the co-occurrence of multiple cardiovascular risk factors that appear together more frequently than by chance alone, though the underlying pathophysiology remains incompletely understood. 1 The syndrome is widely accepted in the medical community as a meaningful clinical entity despite ongoing debate about whether it represents a true syndrome or simply a collection of related phenotypes. 1
The five defining components are:
- Central/abdominal obesity: Waist circumference ≥102 cm in men or ≥88 cm in women 2, 3
- Elevated triglycerides: ≥150 mg/dL (1.7 mmol/L) 2, 3
- Low HDL cholesterol: <40 mg/dL in men or <50 mg/dL in women 2, 3
- Elevated blood pressure: Systolic ≥130 mmHg and/or diastolic ≥85 mmHg 2, 3
- Elevated fasting glucose: ≥100 mg/dL (5.6 mmol/L) 2, 3
Diagnostic Criteria
A diagnosis requires any 3 of the 5 components listed above—no single component is mandatory. 1 This represents the harmonized consensus reached by major international organizations including the International Diabetes Federation, American Heart Association, National Heart Lung and Blood Institute, World Heart Federation, International Atherosclerosis Society, and International Association for the Study of Obesity. 1
The waist circumference thresholds may vary by ethnicity and region, with some populations requiring lower cutoffs, but the other four components use universal thresholds. 1
Clinical Significance and Prognosis
Patients with metabolic syndrome face a 2-fold increased risk of developing cardiovascular disease over the next 5-10 years compared to those without the syndrome. 1, 2 The lifetime cardiovascular risk is undoubtedly even higher. 1
The syndrome confers a 5-fold increased risk for developing type 2 diabetes mellitus. 1, 2 This diabetes risk is particularly pronounced in patients with the combination of insulin resistance and central obesity. 2
The risk escalates proportionally with the number of metabolic syndrome components present—more components mean higher cardiovascular and diabetes risk. 2
Underlying Pathophysiology
Most patients with metabolic syndrome exhibit abdominal obesity and insulin resistance, both of which appear to drive the development of the other metabolic risk factors, though the precise mechanisms remain incompletely understood. 1
Beyond the five diagnostic criteria, patients commonly manifest:
- Atherogenic dyslipidemia: Elevated apolipoprotein B, increased small dense LDL particles, in addition to the elevated triglycerides and low HDL already counted in diagnostic criteria 1
- Prothrombotic state: Elevated PAI-1, factor VII and XII, fibrinogen, reduced tissue plasminogen activator 1
- Proinflammatory state: Systemic inflammation contributing to vascular damage 1
Additional Complications
Microvascular complications occur more frequently: Patients with metabolic syndrome have higher rates of albuminuria (40.8% vs 21.8%) and diabetic retinopathy (37.9% vs 28.6%), with stepwise increases corresponding to the number of components present. 2
Cerebrovascular disease is significantly more common: Metabolic syndrome is present in 40-50% of patients with ischemic stroke, and cerebrovascular disease occurs more frequently in these patients (5.8% vs 3.2%). 2
Cancer risks are elevated: Recent evidence shows metabolic syndrome is associated with increased breast cancer mortality (HR 1.83) and cancer recurrence (HR 1.69) in breast cancer survivors. 2
Public Health Context
The prevalence of metabolic syndrome is rising worldwide, driven largely by increasing obesity rates and sedentary lifestyles, making it both a major public health problem and a critical clinical challenge. 1 The syndrome is not an absolute risk calculator—it doesn't include age, sex, smoking status, or LDL cholesterol—but it identifies a high-risk population requiring aggressive risk factor modification. 1