Metabolic syndrome, the simultaneous occurrence of multiple cardiovascular risk factors, may almost double the risk of stroke, researchers reported at the American Stroke Association's 29th International Stroke Conference.

The findings suggest that treating the risk-factor components of metabolic syndrome might reduce stroke risk before the onset of Type 2 diabetes.

"Before it becomes necessary to begin aggressive treatment of diabetes and other predisposing factors for stroke, it might be possible to take steps to prevent these serious conditions from developing," said the study's lead author, Robert Najarian, a third-year medical student at Boston University School of Medicine.

The US National Cholesterol Education Program (NCEP) and the World Health Organization define the metabolic syndrome as the simultaneous presence of at least three of five metabolic abnormalities: abdominal obesity, high fasting levels of blood sugar, high triglycerides levels, low levels of HDL ("good" cholesterol) and high blood pressure.

This study found that compared to people without metabolic syndrome, men with the condition have a 78 per cent greater risk of stroke, and women affected by the condition have more than double the stroke risk of women who do not have the syndrome. But, the overall stroke risk associated with metabolic syndrome remained below that of people with diabetes.

Metabolic syndrome greatly increases a person's chances of developing Type 2 diabetes. Because of its strong association with diabetes, metabolic syndrome often is considered a prediabetic condition. Both conditions increase the risk of coronary heart disease, and diabetes is a potent risk factor for stroke. However, the relative effect of metabolic syndrome and diabetes on stroke risk has not been studied extensively.

Najarian and his co-investigators compared the impact of metabolic syndrome and diabetes on the 10-year risk of stroke and transient ischemic attack (TIA), a temporary interruption in blood flow to the brain that often precedes a stroke. The study involved 1,881 diabetes-free participants (average age 59) of the offspring cohort in the Framingham Heart Study.

Men and women were evaluated for a current diagnosis of diabetes and the five metabolic syndrome components: abdominal obesity (waist circumference greater than 35 inches in women and greater than 40 inches in men); low HDL (less than 40 mg/dL in men and less than 50 mg/dL in women); blood pressure 130/85 mm Hg or greater, or current treatment with antihypertensive medication; triglycerides 150 mg/dL or greater; and fasting blood glucose of 110-126 mg/dL (the definition of impaired fasting glucose). Participants were considered to have the metabolic syndrome if they met at least three of the five criteria.

Najarian found that 27.6 per cent of the men and 21.5 per cent of the women met the criteria for a diagnosis of metabolic syndrome without including diabetes. When the additional 216 participants with diabetes were included in the analysis, 30.3 per cent of men and 24.7 per cent of women met diagnosis criteria.

During a maximum follow up of 14 years, 5.6 per cent of the men in the study and 4.3 per cent of the women had a stroke or TIA.

Diabetic patients had a significantly higher 10-year risk of stroke compared to people with metabolic syndrome: 14 per cent vs 8 per cent in men and 10 per cent vs. 6 per cent in women.

Although metabolic syndrome is a less potent risk factor for stroke than diabetes, the condition occurs more often than diabetes, making it a major consideration for stroke risk and prevention, Najarian said. Interventions aimed at preventing or treating metabolic syndrome could have a major impact on overall stroke risk.

"Metabolic syndrome looks like the precursor for a number of health problems," Najarian said. "Because the prevalence of the syndrome is so high, we need to start thinking about how to prevent the condition, particularly since it appears to be a factor in the continuum that leads to outright diabetes and cardiovascular disease. The end result is a higher death rate from all causes, a higher death rate from vascular causes, and higher rates of cardiovascular disease."