The metabolic syndrome comprises a constellation of risk factors associated with atherosclerotic cardiovascular disease, type 2 diabetes and their complications. The major causes of the metabolic syndrome are intra-abdominal adiposity and insulin resistance.
Differences in body-fat distribution associated with an altered metabolic profile were documented in the medical literature 50 years ago and it was dubbed Syndrome X in 1988 (Grundy et al, 2004). The World Health Organization (WHO) published the first clinical definition of the metabolic syndrome in 1998 (Alberti and Zimmet, 1998), which was revised the following year (WHO, 1999). The National Cholesterol Education Programme published a revised definition in 2002 (Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults). This was followed in 2005 by the International Diabetes Federation’s (IDF’s) definition (Alberti et al, 2005), which was most recently revised in 2006 (IDF, 2006). The IDF definition stresses the presence of central obesity in diagnosing the metabolic syndrome.
As a result of current lifestyle choices and increasing obesity, the metabolic syndrome is becoming a major global health problem. Studies in the US have shown that more than one half of adults are obese or overweight (Centers for Disease Control and Prevention, 2008). It has been estimated that the metabolic syndrome will soon overtake cigarette smoking as the primary risk factor for cardiovascular disease (Eckel and Krauss, 1998). Grundy et al (2004) reported that the metabolic syndrome is an even stronger predictor of type 2 diabetes than traditional risk factors. However, there are very limited data published that examine the metabolic syndrome among the young British population.
Methods
We conducted an observational study over a 15-month period from September 2003 to December 2004. All young people (<45 years of age) presenting to University Hospital Aintree, Liverpool with an acute myocardial infarction, both ST segment elevation and non-ST segment elevation, were examined. Our study consisted of 68 consecutive people who fell into this category.
The IDF definition (2006) was used to determine the presence of the metabolic syndrome. Central obesity was used as the primary criterion. Where two or more of the four factors listed in Table 1 were found in addition to central obesity, the person was defined as having the metabolic syndrome. A BMI >28kg/m2 was substituted for a waist circumference ≥94cm for Europid men and ≥80cm for Europid women in the definition of obesity. This substitution is one most observers would accept as satisfactory and was previously used by Ridker et al (2003) in their analysis of the metabolic syndrome in the Women’s Health Study.
Results and statistical analysis
Of the 68 people included in the study, 53 had all the necessary data to determine the presence or absence of the metabolic syndrome. Of these, a significant number of people (n=39, 73.6%) met the IDF criteria for having the metabolic syndrome.
Differences were found in the mean blood pressure, BMI, and fasting glucose, total cholesterol and triglyceride levels between those with and without the metabolic syndrome (Table 2). Among those with the metabolic syndrome (n=39), three (7.7%) had a history of diabetes and a further nine (23.1%) were diagnosed with diabetes at the time of presentation. Among those without the metabolic syndrome (n=14), one (7.1%) had a history of diabetes and one (7.1%) was diagnosed with diabetes at the time of presentation (Figure 1). In total, the prevalence of diabetes was more than double in those with the metabolic syndrome (30.8%) as compared to those without the metabolic syndrome (14.3%). Analysing the between group difference yielded a chi-squared value of 0.48 with a 95% confidence interval of 0.31–0.65. As the confidence interval does not contain zero, the difference between the groups is statistically significant (Table 3).
Discussion
This pilot observational study in our institution demonstrates that a significant proportion of young people with the metabolic syndrome are at high risk of acute myocardial infarction and type 2 diabetes. In the UK healthcare system, this association will have particular relevance in the primary care setting; these high-risk individuals need to be identified and treated to avoid increased risk for the associated complications. Grundy et al (2004), in their report for the American Heart Association and the National Heart, Lung and Blood Institute, state that “because of a documented high relative risk for atherosclerotic coronary vascular disease events and type 2 diabetes, the metabolic syndrome undoubtedly carries a relatively high lifetime risk for these disorders even when short term (10 years) risk is in the low to moderate range.”
Grundy et al (2005) reported that the risk for atherosclerotic coronary vascular disease associated with the metabolic syndrome is greater than the sum of its risk factors and the risk rises geometrically, not linearly. Further, they suggested that management of the metabolic syndrome is a secondary target for reducing cardiovascular events, while smoking cessation, lowering LDL-cholesterol levels and blood-pressure management are the primary targets for risk reduction. Lifestyle interventions to mitigate the modifiable risk factors, such as obesity, physical inactivity and atherogenic diet, are the initial therapies recommended for treatment of the metabolic syndrome (Grundy et al, 2005). The current available evidence suggests that individuals with the metabolic syndrome may benefit from behavioural therapy targeted towards weight loss and exercise. Knowler et al (2002) and Tuomilehto et al (2001) have both demonstrated that such lifestyle measures can reduce the risk of diabetes by up to 58%.
If lifestyle changes are not sufficient to manage the risks associated with the metabolic syndrome, drug therapies for abnormalities of the individual risk factors may be necessary. Promisingly, more recent therapies have been developed that target the possible underlying cause of the metabolic syndrome (intra-abdominal adiposity).
Our study is limited by the small number of people involved. All of the people studied were British Caucasians, and lived in the same geographical area. Reproducing this study with a larger sample size, and the involvement of a number of geographical regions, would provide valuable data on the metabolic syndrome as a risk factor for myocardial infarction and diabetes in the wider population of people aged <45 years.
Identifying young people at high risk of the metabolic syndrome in our communities is becoming increasingly important. Identifying these young people will allow healthcare professionals to initiate lifestyle interventions and therapies with the aim of decreasing long-term morbidity and mortality.
Acknowledgements
We are thankful to Mr. Steven Lane, University of Liverpool for his kind assistance with statistical analysis.
What can we do in practice to reduce the risk of this common yet underdiagnosed microvascular complication of diabetes?
12 Dec 2024