Isolated systolic hypertension in Evans county--I. Prevalence and screening considerations

Studies suggest that isolated hypertension involves pathophysiological change different from essential hypertension; while clinical trials of drug treatment of isolated systolic hypertension are underway, little is known of its descriptive epidemiology. This paper reports characteristics of isolated systolic hypertension in biracial Evans County, Georgia, 1967-69. Isolated systolic hypertension was rare below age 40, but the percent prevalence increased greatly at older ages. Defining isolated systolic hypertension as diastole blood pressure (DBP) less than 95 and systolic blood pressure (SBP) greater than 160, age-adjusted percent prevalence at ages 40 and above were 9.6, 10.6, 15.1, and 18.3 for white males, black males, white females, and black females respectively. Percent prevalence declined to 4.8, 6.3, 9.7, and 12.7 in the four race/sex groups when a DBP cutoff of 90 was used. Unlike essential hypertension, percent prevalence of isolated systolic hypertension varied more by sex than by race: it was 60-100% higher in females than in males and only 10--30% higher in blacks than in whites. Percent prevalence of isolated systolic hypertension for the second and third of three BP readings (one clinic visit) increased compared to the first reading, the reverse of what is usually found for essential hypertension. DBP variability was relatively greater than SBP variability and probably accounted for the changes in percent prevalence. These data support clinical studies indicating isolated systolic hypertension is a distinct syndrome. This condition, shown to be a risk factor for death and disease in other studies, was common at older ages and may increasingly become health problem as the population ages.