Risk Factors for Cardiovascular Illness and Their Prevalence in Patients With Schizophrenia

As with many chronic disorders, prevention is the key, and patients with schizophrenia possess numerous modifiable cardiovascular risk factors that may be the focus of intervention. As Osby et al. (2000) concluded, "The number of excess deaths, rather than increased SMRs, may be the target for preventive programs since the aim of prevention should be to reduce this excess mortality" (p. 25). The literature on cardiovascular risk factors is rapidly evolving, but a core group of modifiable risk factors have emerged as targets for treatment (Table 4-1). Individuals at risk present with a constellation of modifiable and nonmodifiable risk factors, with the latter including age, gender, family history, personal history, and genetic predisposition toward high CHD risk by various mechanisms inducing

Table 4-1. Modifiable risk factors for cardiovascular disease and their prevalence in patients with schizophrenia

Risk factor

Prevalence in schizophrenia (%)

Elevated total cholesterol

>18

Hypertension

13.7-19.7

Smoking

70

Overweight or obesity

42-55

Sedentary lifestyle

72

obesity, dyslipidemias, and diabetes mellitus. Although the prevalence of most modifiable CHD risk factors in schizophrenia is higher than in the general population, there is no evidence that patients with schizophrenia are genetically predisposed to cardiovascular disease in a manner not explicable by traditional risk factor analysis. There are two lines of evidence to support this conclusion. Postmortem evaluation of schizophrenic patients earlier this century demonstrated findings of hypoplasia of the heart and great vessels, but recent necropsy studies, such as that by Coffman et al., that exclude patients with known cardiovascular diseases have not found statistically significant differences in measures of left atrial, aortic root, or end-diastolic left ventricular diameter (Coffman et al. 1985). Moreover, reviews of sudden-death cases involving patients with schizophrenia reveal that typical natural causes such as atherosclerotic cardiovascular disease constitute the majority of etiologies once suicide and accidents are excluded (Chute et al. 1999; Ruschena et al. 1998).

The current understanding of cardiovascular risk factors comes from large, longitudinal epidemiological studies such as the Framingham Heart Study (Wilson et al. 1988) and the Multiple Risk Factor Intervention Trial (MRFIT; Stamler et al. 1986). These studies have helped elucidate the contributions of age, family history of CHD, gender, smoking, overweight and obesity, diabetes, hypertension, diet, lifestyle, and serum cholesterol to overall cardiovascular risk. In particular, MRFIT, a longitudinal 6-year study of 356,222 individuals, demonstrated the linear relationship between serum cholesterol and CHD deaths. Biological effects independent of lifestyle variables (e.g., smoking, activity, diet) thus contribute on average approximately 40%-60% to overall CHD risk (Engstrom et al. 2000). Those in the highest risk group are persons with established CHD or equivalent disorders, defined as those pathologies that, along with established CHD, exhibit a >20% 10-year risk for major coronary events such as fatal or nonfatal MI, unstable angina, or sudden death. These CHD equivalent disorders include diabetes mellitus and other clinical forms of atherosclerotic disease (peripheral arterial disease, abdominal aortic aneurysm, and symptomatic carotid artery disease). The National Cholesterol Education Program (NCEP) published its third series of revised guidelines for management of cholesterol and cardiovascular risk in 2001, and included diabetes as a CHD equivalent for the following reason: "Diabetes counts as a CHD risk equivalent because it confers a high risk of new CHD within 10 years, in part because of its frequent association with multiple risk factors. Furthermore, because persons with diabetes who experience MI have unusually high death rates either immediately or in the long term, a more intensive prevention strategy is warranted" (Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults 2001, p. 2487).

For those without established CHD or CHD equivalent disorders, 10-year cardiovascular risk estimates can be performed quite simply with a risk chart such as that created by the NCEP on the basis of data from the Framingham study and trials of lipid-lowering agents (Table 4-2). These charts are gender specific and use data on age, smoking status, systolic blood pressure, and both total serum cholesterol and high-density lipopro-tein (HDL) cholesterol to generate the risk estimate for a major coronary event over the next decade. Points are assigned to each risk factor, and total points are converted to risk estimates expressed in percentages.

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