Prevalence of Plasma Lipoprotein Abnormalities in a Free-Living Population of the Central Valley, California

Abstract

In an epidemiologic study of 1,118 free-living volunteers, aged 25 to 79 (552 male, 566 female) drawn from eight counties of the Central Valley, California, the following determinations were included: a medical history, blood pressure, resting electrocardiogram, plasma total cholesterol and glycerides (following a light, fat-free breakfast), and (when lipids were considered to be elevated) plasma lipoproteins determined by electrophoresis. A subgroup of the entire study population (494 male, 503 female) free of overt diabetes and electrocardiographic abnormalities, and with diastolic blood pressure not above 100 mm Hg, that was considered to be clinically "normal," forms the basis of this report. Significant sex differences for mean levels of total cholesterol were absent or of small magnitude at all age decades up to and including the seventh. In contrast, glyceride levels for men were significantly higher than for women aged 25-59, and differences were substantial. Beyond the seventh decade, females had higher mean levels of both plasma total cholesterol and glycerides. The type IV lipoprotein pattern was the most common abnormality (8.6%) within the entire normal population and was 2.7 times as common in men (13%) as in women (4.8%). Type II pattern was less common overall (3.7%) and was more frequent in women than in men. Types III (0.2 to 0.4%) and V (0.2%) were both very uncommon, and type I was not encountered. Results were similar when the entire population (normal and abnormal) was considered. These findings suggest that sex differences in plasma total-cholesterol level cannot account for the known male preponderance in coronary heart disease within the population studied. Prolonged elevation of plasma glycerides (usually expressed as the type IV pattern) in males during the years when atherogenesis is occurring might account for the sex difference.