What defines metabolic syndrome?

What Defines Metabolic Syndrome

Metabolic syndrome is diagnosed when a patient has at least 3 of the following 5 criteria: elevated waist circumference (≥102 cm in men, ≥88 cm in women), elevated triglycerides (≥150 mg/dL), low HDL cholesterol (<40 mg/dL in men, <50 mg/dL in women), elevated blood pressure (≥130/85 mmHg), and elevated fasting glucose (≥100 mg/dL). 1, 2

The Five Diagnostic Components

The harmonized international definition requires any 3 of these 5 criteria to be present 1:

1. Abdominal Obesity (Waist Circumference)

• Men: ≥102 cm (40 inches) 1, 2
• Women: ≥88 cm (35 inches) 1, 2
• Note that ethnic-specific cut points may be more appropriate for certain populations 3

2. Elevated Triglycerides

• ≥150 mg/dL (1.7 mmol/L) 1, 2
• Or on drug treatment for elevated triglycerides 1

3. Reduced HDL Cholesterol

• Men: <40 mg/dL (1.03 mmol/L) 1, 2
• Women: <50 mg/dL (1.29 mmol/L) 1, 2
• Or on drug treatment for reduced HDL 1

4. Elevated Blood Pressure

• Systolic ≥130 mmHg and/or diastolic ≥85 mmHg 1, 2
• Or on antihypertensive drug treatment 1

5. Elevated Fasting Glucose

• ≥100 mg/dL (5.6 mmol/L) 2, 4
• Note: The original ATP III definition used ≥110 mg/dL, but this was updated to ≥100 mg/dL in the harmonized 2009 consensus 1
• Or on drug treatment for elevated glucose 1

Clinical Significance and Risk

Understanding why this matters for your patients:

• Cardiovascular disease risk: Patients with metabolic syndrome have a 2-fold increased risk of developing CVD over 5-10 years compared to those without the syndrome 1, 2, 4
• Diabetes risk: The syndrome confers a 5-fold increased risk for type 2 diabetes mellitus 1, 2, 4
• Mortality: Men with metabolic syndrome have a 4-fold increase in fatal coronary heart disease and 2-fold greater risk of all-cause mortality 1

Key Differences from Historical Definitions

The 2009 harmonized definition resolved earlier controversies 1:

• No single component is mandatory (unlike the WHO definition which required insulin resistance, or the IDF definition which required abdominal obesity) 1
• Any 3 of 5 criteria suffice for diagnosis, making it more practical for clinical use 1, 2
• Insulin resistance measurement is not required, though it remains a key underlying pathophysiologic feature 1

Common Pitfalls to Avoid

• Don't overlook waist circumference measurement - this is frequently not measured in clinical practice despite being a required component 3
• Remember the updated glucose threshold - the current cutoff is ≥100 mg/dL, not the older ≥110 mg/dL threshold 2
• Consider ethnic variations - Asian populations may require lower waist circumference thresholds 3
• Don't confuse metabolic syndrome with absolute cardiovascular risk - the syndrome doesn't include age, sex, smoking, or LDL cholesterol, which are critical for calculating absolute risk 1