Metabolic syndrome, also known as Syndrome X and insulin resistance syndrome, is characterized by the concurrence of several component parts, including insulin resistance (leading to elevated insulin levels or hyperinsulinemia), elevated blood sugar levels, overweight with increased abdominal fat, atypical cholesterol levels, and high blood pressure. The condition appears to stem largely from a genetic predisposition combined with a sedentary lifestyle and an unhealthful diet.

Varying definitions of metabolic syndrome have existed over the years, with different cutoffs used for the components of the condition. Recently, however, both the National Cholesterol Education Program (NCEP) and the World Health Organization published new definitions. When applying the NCEP definition, approximately one-third of middle-aged men and women in the United States have the metabolic syndrome.

Researchers have known for some time that metabolic syndrome is associated with the subsequent development of type 2 diabetes and cardiovascular disease (CVD). Now, in a study published in the Journal of the American Medical Association (JAMA), researchers show that middle-aged men with metabolic syndrome are at an increased risk for death due to CVD as well as death from any cause.

About the Study

Researchers from Louisiana State University studied 1209 Finnish men aged 42 to 60 who were enrolled in the Kuopio Ischaemic Heart Disease Risk Factor Study between 1984 and 1989. At the time of enrollment, none of the men had CVD or diabetes.

Over a follow-up of approximately 11.4 years, the scientists measured death due to coronary heart disease (CHD) alone, by all types of CVD (including CHD), and by any cause in men with and without metabolic syndrome. A diagnosis of metabolic syndrome was made based on measurements of blood pressure, body mass index (a ratio of weight to height), waist circumference, waist-hip ratio, blood glucose, insulin, HDL cholesterol, and triglycerides.

Because there is some lack of consensus on the definitions of metabolic syndrome, the researchers used four definitions of metabolic syndrome specified by the NCEP and WHO as follows:

NCEP Definition 1 (at least three of the following):

  • Fasting plasma glucose greater than or equal to 110 mg/dL (6.1 mmol/L)
  • Abdominal obesity: waist girth greater than 102 cm
  • Serum triglycerides greater than or equal to 150 mg/dL (1.7 mmol/L)
  • Serum HDL cholesterol less than 40 mg/dL (1.0 mmol/L)
  • Blood pressure greater than or equal to 130/85 mm Hg

NCEP Definition 2:
Same as Definition 1 except abdominal obesity: waist girth greater than 94 cm

Modified WHO Definition 1:

  • Abnormally elevated insulin levels (hyperinsulinemia) or fasting plasma glucose greater than or equal to 110 mg/dL (6.1 mmol/L)
AND at least two of the following:
  • Abdominal obesity: waist-hip ratio greater than 0.90 or BMI greater than or equal to 30
  • Serum triglycerides greater than or equal to 150 mg/dL (1.7 mmol/L) or HDL cholesterol less than 35 mg/dL (0.9 mmol/L)
  • Blood pressure greater than or equal to 140/90 mm Hg

Modified WHO Definition 2:
Same as Definition 1 except abdominal obesity: waist girth greater than or equal to 94 cm

The Findings

The findings of the study vary according to which definition is used. For example, a total of 8.8–14.3% of the population had metabolic syndrome. According to the NCEP definitions, men with metabolic syndrome were 2.9 to 4.2 times more likely to die of CHD than men without metabolic syndrome. When using the WHO definitions, men with metabolic syndrome were 2.9 to 3.3 times more likely to die of CHD. The researchers adjusted for potentially confounding conventional cardiovascular disease risk factors such as smoking and LDL cholesterol levels.

Men with metabolic syndrome as defined by the WHO were also 2.6 to 3.0 times more likely to die of CVD, and 1.9 to 2.1 times more likely to die of any cause compared to men without metabolic syndrome. The NCEP definition was a less consistent predictor of death from CVD or any cause.

The research findings are striking, but there are important limitations to the study. First, the researchers did not study women, older individuals, or anyone who was not living in Finland so further study will be needed to determine whether the results apply to other populations. In addition, there were a limited number of deaths from CHD over the course of the study (27 CHD deaths over a 11.4-year follow-up), so the effects of metabolic syndrome on CHD mortality may seem exaggerated as expressed above.

How Does This Affect You?

This study demonstrates that metabolic syndrome can increase your risk of death, even before development of CVD or diabetes. So what can you do to prevent metabolic syndrome? While some evidence exists that moderate to vigorous physical activity reduces the risk of metabolic syndrome, research to date has primarily focused on the component parts of the syndrome. For example, there is now substantial evidence that adopting lifestyle changes including exercise and a healthful diet can, in many cases, lower glucose and blood pressure levels to the normal range.

Follow these tips to help control the components of metabolic syndrome:

  • If you smoke, quit.
  • Eat a healthful diet, low in saturated and trans fats and high in whole grains, fruits, and vegetables.
  • Do 30 minutes of moderate exercise most days of the week.
  • Maintain a healthy weight; lose weight if necessary.
  • Drink alcohol in moderation. Moderate alcohol intake is no more than 2 drinks per day for men and 1 drink per day for women.