Changing patterns of acute myocardial infarction: decline in period prevalence and delay in onset.

The rural Pee Dee area of South Carolina has had the highest mortality rate in the nation for coronary heart disease. Community surveillance shows a 22.7% (p = 0.0008) decline in fatal and nonfatal acute myocardial infarction (AMI) rates during the period 1978 to 1985 in the Pee Dee area. Rates for white men decreased 32% (p = 0.001), whereas in other race-sex groups changes were not significant, although there was a downward trend (p = 0.18) among black men. Among white men decreases in the AMI rates occurred in each of the decades of age 35 to 64 years. In all race-sex groups there was a sharp increase in rates between 1978 and 1985 for those 65 to 74 years of age, suggesting that the incidence of AMI was delayed to a later age. Out-of-hospital AMI death rates declined markedly in all race-sex groups: 63% for white men, 62% for white women, 49% for black men, and 39% for black women. Overall case fatality rates declined from 14% (27 of 193) to 10% (23 of 232), but the decrease was not statistically significant.