The correlation of epidemiological variables

Data from a sizable hospital-based, case-control study from 1985 to 1990 permitted us to examine the correlation of variables by degree of interrelationship. The variables examined relative to their confounding interrelationships include smoking; consumption of alcohol, coffee, meat, vegetables, and fruits; body mass index; education, and age. The variables with the broadest impact on others are age and education. While the association among these variables is generally known, the degree of association made possible by our large database is generally not fully appreciated and is of obvious significance when data are adjusted for one other variable. In some instances, the intercorrelation among different variables is relatively complicated. For instance, cigarette smoking correlates positively with meat consumption and negatively with intake of fruits and vegetables, which, in turn, correlates with alcohol intake. These interrelationships need to be clearly understood before interpreting epidemiologic data for causation. In general, the correlations are similar for men and women. This study of correlation of variables, some expected and some unexpected, should be of value as a source to epidemiologists and provide a useful base.