Introduction: Between 1960 and 2006, stroke mortality in the U.S. has declined a remarkable 65% for white men (123.4 ◊ 42.8 per 100,000), 61% for white women (108.6 ◊42.3 per 100,000), 67% for non-white men (178.4 ◊ 59.5 per 100,000) and 70% for non-white women (175.2 ◊ 52.0 per 100,000). With hypertension being the predominant risk factor for stroke, we examined the population shift in systolic blood pressure (SBP) levels over this period.
Methods: The Charleston Heart Study (CHS) and Evan County Study (EC) were population-based cohorts recruiting black and white participants in the early 1960’s, conducted in the coastal plain regions of SC and GA respectively. REasons for Geographic And Racial Differences in Stroke (REGARDS) is a population-based study recruiting black and white participants in the contiguous U.S. For purposes of this report, CHS/EC participants were limited to those over 45 years, and REGARDS participants were restricted to residents of the coastal plain of NC/SC/GA.
Results: SBP data are available on 1,988 whites and 1,172 blacks from CHS/EC, and from 4,057 whites and 2,237 blacks from REGARDS. Dramatic changes in the distribution of SBP have occurred over these 40+ years, with the 25th percentile of CHS/EC being consistently above the 75th percentile for REGARDS (see figure). For example, for whites aged 65-74, the 25th, 50th, and 75th percentile of SBP in CHS/EC was 144-162-184 mmHg, compared to 118-126-137 mmHg in REGARDS. For blacks, the corresponding percentiles were 158-180-204 mmHg in CHS/EC, and 119-129-140 mmHg in REGARDS. In CHS/EC, 125 of 1988 (6%) whites, and 245 of 1172 (20%) blacks had a SBP of 200+ mmHg; compared to only 4 of 4057 (0.1%) whites and 3 of 2235 (0.1%) blacks in REGARDS.
Discussion: A dramatic shift in the distribution of systolic blood pressure, likely related to both population shifts in blood pressure and the advent of antihypertensive therapy, is likely a major contributor to the steep decline in stroke mortality.