Is the recent decline in coronary heart disease mortality in the United States attributable to lower rates of influenza and pneumonia

A downturn in coronary heart disease (CHD) mortality in the United States has been observed since 1968, and an acceleration in the long-term decline in stroke deaths began in the early 1970s. In considering the causes of this secular trend, attention has been drawn to the parallel downturn in deaths from influenza and pneumonia. The slope of the downward trend for the cardiovascular causes in the summer equals that of the winter, when the potential impact of a decrease in respiratory infection would be greatest. In addition, trends in the death rate from influenza and pneumonia tended to lag behind that of CHD and stroke, in relation to each of the four sex-race groups, the magnitude of the slope of the mortality curve, and the month-by-month variation. Although cause and effect relationships cannot be defined from vital statistics alone, it would appear that the decline in cardiovascular diseases has been the primary phenomenon, reducing the number of persons in the population susceptible to respiratory infection.