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We analyzed long-term trends in the incidence of a first acute myocardial infarction and in case-fatality rates among employees of the Du Pont Company from 1957 through 1983. A steady decline in incidence was observed among male employees. The annual age-adjusted rate in the 1957-1959 period was 3.19 per 1000, as compared with 2.29 per 1000 in the 1981-1983 period--a decline of 28.2 per cent. The rate of decline was higher among salaried (white-collar) employees than among production workers receiving hourly wages. No trend was seen among female employees, but the number of cases may have been to small to detect a decline. Beginning in 1969, the 24-hour case-fatality rate showed a moderate decline, but after 1975, there was a sharp drop in the 30-day case-fatality rate among persons who survived 24 hours after the attack. These declines did not begin until several years after the decline in incidence had begun. This study and others suggest that improved medical care probably made some contribution to the decline in mortality associated with coronary heart disease, but the major source of the decline has been a reduction in the incidence of the disease.

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