Metabolic syndrome

So far risk factors for cardiovascular disease (CVD) have been discussed individually in relation to the effects of physical activity (see Chapter 4). However, some risk factors tend to cluster together. These include dyslipidaemia (specifically, high triglycerides and low high-density lipoprotein (HDL)-cholesterol), impaired glucose regulation or diabetes, obesity (particularly visceral obesity) and hypertension. The phrase ‘cluster together’ means that these risk factors coexist more commonly than would be expected by chance. For example, diabetes and obesity are twice as common among people with hypertension as among those with normal blood pressure. As a combination, risk

Introduction 148 ❚

Causal factors 151 ❚

Prevention 161 ❚

Summary 162 ❚

Study tasks 163 ❚

Note 163 ❚

Further reading 163 ❚

factors become much more powerful predictors of disease. Data from the Framingham Offspring Study1 shows that clusters of three or more factors increased the risk of coronary heart disease (CHD) more than two-fold in men and nearly six-fold in women (Figure 7.1). This clustering of risk factors is important for at least three reasons: first, it suggests the existence of a common aetiology; second, it makes it difficult to treat people because drugs are designed to target one pathology, not several; and third, (as the reader will realize) physical activity may be an especially attractive preventive and/or therapeutic intervention if it is beneficial for more than one component of the cluster. A group of symptoms or abnormalities that occur together, making a pattern, are called a syndrome. The name most commonly given to the constellation of disturbances identified above and associated with elevated risk for CVD and type 2 diabetes is ‘metabolic syndrome’.