The constitutional element in the etiology of pneumonia.

Abstract

A detailed genetic and biometric study has been made of a family of 13 brothers and sisters all of whom have had broncho or lobar pneumonia one or more times. One has had it twice, and one has had it three times. Seven of the 13 have died of it. One has tuberculosis of the lungs, and another presents clinical symptoms which make it probable that he also has. There have been in the sibship 87.2 person-years exposure to risk, counting the “infant” deaths to have occurred at 0.3 year, which is probably as fair as any other assumption, it having been shown that the deaths of the first year of life center at 0.3 year. In these 87.2 person-years of exposure occurred 16 cases of pneumonia, or 18 per 100, and 7 deaths, or 8 per 100 person-years exposure. Unfortunately, owing to lack of morbidity data, we cannot make any exact comparison of the case incidence rate of pneumonia in this family with that in the general population. But that it is enormously higher is obvious. Every day experience indicates that nothing like 100 per cent of all persons have pneumonia before reaching the age of 19.

In the case of mortality a more exact approach is possible. If the age-specific mortality rates for pneumonia in the U. S. Registration Area (exclusive of North Carolina) in 1910 are applied to a group of 13 children having the same age distribution as the sibship under discussion, the results shown in Table 1 are obtained.

It is thus seen that there had occurred in the particular sibship studied, up to the time of this investigation, more deaths from pneumonia than would be expected in twenty-five families of this size on the basis of the usual mortality from this cause.