Family history as a risk factor for coronary heart disease in South African families

This article presents data on, and applies a procedure for the statistical quantification of, family history as a risk factor for coronary heart disease (CHD) in three sub-samples (groups) of families: I--a healthy control group; II--families with familial hypercholesterolaemia (FH); and III--families identified by an index case with CHD. With regard to the average family history of CHD (calculated as an index for each family, and as a mean index for each group), group II differs significantly from group I and marginally significantly from group III; family groups I and III do not differ from each other statistically. By means of significance tests developed for this purpose, the groups of families are shown to be significantly heterogeneous, by being composed of families highly resistant against and susceptible to CHD. This is illustrated for example in group II, where some FH families can be shown to be highly resistant to CHD, compared with other FH families with a very strong history of CHD. The exact number and proportion of such families at different levels of significance is calculated and the actual families with the highest and lowest calculated family indices, respectively, are then identified (illustrated by examples). The practical significance of the statistical procedure of quantifying and applying family history as a risk factor for CHD, is discussed in terms of epidemiological and preventive health considerations.