Risk Factors for Cardiovascular Disease

Evidence has shown that lifestyles associated with a ‘western’ culture such as a diet rich in saturated fats and high in calories, smoking and physical inactivity, are some of the modifiable risk factors leading to an increase in the prevalence of CVD. Of these, three are considered to be of prime importance:¹

• Smoking is responsible for 50% of all avoidable deaths, of which half are due to CVD.
• Raised blood pressure has been found to be an important risk factor for the development of CVD, cardiac failure and cerebrovascular disease. The greater the increase in blood pressure, the higher the risk. Greatest benefit of blood pressure lowering is seen in those at higher risk. Even modest reductions produce substantial benefits in those with multiple risk factors.
• Dyslipidaemia, in particular, raised low-density lipoprotein (LDL) cholesterol and triglyceride levels, and low high-density lipoprotein (HDL) cholesterol are associated with increased risk of CVD.

Levels of Risk Associated with Smoking, Hypertension and Hypercholesterolaemia

Multiple risk factors for CVD are usually present in an individual; rarely do they occur in isolation. When risk factors co-exist the effect is often exponential; their combined effect is greater than the sum of their individual effects.²

Multiple risk factors are also associated with the metabolic syndrome which is characterised by dyslipidaemia, hypertension, insulin resistance, visceral distribution of body fat, and a prothrombotic state.³

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*Reproduced with permission from Radcliffe Medical Press.

The Metabolic Syndrome and Associated CVD Risk Factors

The metabolic syndrome is characterized by insulin resistance, visceral distribution of body fat, dyslipidaemia, hypertension, and a prothrombotic state. All the components of the metabolic syndrome are associated with endothelial injury and dysfunction, the primary event that results in atherosclerosis. In particular, it is characterised by the lipid triad of elevated triglycerides, low high-density lipoprotein (HDL), and small, dense low-density lipoprotein (LDL) particles.³

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*Adapted from Am J Med 1998;105(1A):1S–3S, with permission from Excerpta Medica.

Overweight and Obesity as a Risk Factor

Approximately 220,000 deaths in the US and Canada, and 320,000 deaths in Western Europe (20 countries) per year can be attributed to obesity.^4,5 The obesity epidemic has reached unprecedented proportions in Western society, and represents a growing threat to health in an increasing number of countries worldwide.^4,5

Obesity, especially abdominal obesity, represents a strong independent risk factor for CVD and is associated with the metabolic syndrome.

The metabolic syndrome is characterised by the presence of other multiple other risk factors for CVD including dyslipidaemia, hypertension and insulin resistance, all of which tend to cluster in abdominally obese individuals.^4,5

The Progression from CV Risk Factors to Endothelial Injury and Clinical Events

Well-recognised cardiovascular risk factors (hypertension, dyslipidaemia, diabetes, smoking, etc) are associated with changes in the vessel wall that lead to cardiovascular disease.

One of the earliest changes associated with these risk factors is an increase in oxidative stress in the vessel wall. This causes endothelial cells to decrease production of some compounds and increase production of others.⁶

Production of nitric oxide (NO), a powerful vasodilator, is decreased. Production of vasoconstrictors, notably endothelin and angiotensin II (Ang II), is increased. Greater production of local mediators (eg. vascular cell adhesion molecule [VCAM], and plasminogen activator inhibitor 1 [PAI-1]) promotes inflammation, disrupts fibrinolysis, increases vascular remodeling and plaque rupture. The vascular endothelium secretes numerous other substances that modulate blood vessel tone and participate in the development and progression of atherosclerosis. Thus, the presence of cardiovascular risk factors begins a progression that sets the stage for clinical events.

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References:
1. Pyörälä K et al. Eur Heart J 1994;15:1300–1331.
2. Poulter N. In Cardiovascular Disease: Risk Factors and Intervention. Eds: Poulter N, Sever P, Thom S. Radcliffe Medical Press, Oxford, 1993.
3. Deedwania PC. Am J Med 1998;105(1A);1S–3S.
4. World Health Organization. The World Health Report 2002.
5. International Cardiovascular Disease Statistics 2005; American Heart Association.
6. Gibbons GH, Dzau VJ. N Engl J Med 1994;330;1431–1438.

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