Prospective studies on coronary heart disease in the elderly : the role of classical and new risk factors

In this thesis associations between biological risk factors and the occurrence of coronary heart disease in elderly persons are described. The focus is on classical (i.e. total and high density lipoprotein cholesterol and blood pressure) and some new (i.e. homocysteine, white blood cell count and serum albumin) biological risk factors. The studies are based on two Dutch cohorts. One is a cohort of 292 men and women, aged 64 to 87 years in 1971, from a general practice in Rotterdam, with a mortality follow-up of 17 years. The other is the Dutch cohort of the Seven Countries Study which consists of 939 men aged 64 to 84 years in 1985 from the town of Zutphen. The morbidity and mortality follow- up embraced five years.In general, the classical risk factors were important predictors of coronary heart disease occurrence in elderly people. Systolic blood pressure was a strong independent long-term predictor of coronary heart disease mortality in elderly women, but the long-term association was less clear in elderly men. Total cholesterol was also significantly associated with long-term mortality from coronary heart disease in elderly women, but in men the association tended to be inverted <em>U</em> -shaped, i.e. men with cholesterol levels in the median tertile of the cholesterol distribution had a higher risk than those with levels in the first and third tertile. Regarding the Zutphen study, the short-term associations with incidence of coronary heart disease were usually weaker than with mortality from the disease. Elevated systolic and diastolic blood pressure, and especially isolated systolic hypertension, were important short-term predictors of sudden cardiac death in elderly men. For mortality from coronary heart disease, which was not additionally recorded as sudden, <em>U</em> -shaped associations with systolic and diastolic blood pressure levels were observed, i.e. men with the lowest blood pressure levels and those with the highest blood pressure levels and using antihypertensive medication had the highest risk. Serum total cholesterol was related to short-term coronary heart disease mortality in elderly men. For incidence of the disease, an association was only observed in a subgroup of the population with serum albumin levels below the median. High density lipoprotein cholesterol was not predictive of mortality from coronary heart disease, but there appeared to be an association with the incidence of the disease.Concerning the new risk factors, serum homocysteine appeared to be associated with mortality from coronary heart disease in elderly men in the first one-and-a-half years of follow-up only. A strong association with mortality from cerebrovascular disease was observed in normotensive men. In addition, an association with an increased risk of cognitive impairment was suggested. Both white blood cell count and serum albumin were important predictors of coronary heart disease independent of the classical risk factors for coronary heart disease. The association with serum albumin could only partly be explained by baseline health status indicators.The experience obtained from the studies described in this thesis has made clear that elderly people are a heterogenous group with respect to risk factor levels as well as coronary heart disease risk. It would therefore be desirable to have a measure of susceptibility for coronary heart disease to identify elderly people who are at increased risk of the disease. Our studies suggest that white blood cell count and serum albumin, routine clinical blood chemistry values, may be useful in this respect in addition to the classical risk factors. Future studies should aim at assessing the effectiveness of a multifactorial approach of risk factor management on coronary heart disease and all-cause mortality as well as on quality of life in older men and women.