Apparent heterogeneity of the risk of a disease in different groups ma
y be explained by subject-specific risk factors unequally distributed
in these groups. We propose a score test of homogeneity that allows ad
justment for known risk factors of the disease; The test is based on a
random-effect logistic regression model and requires only simple comp
utations in addition to a conventional logistic regression method. The
score test is applied to the study of geographical heterogeneity of c
ognitive impairment in elderly using a sample of 3,318 subjects scatte
red in 75 parishes. It is shown that an apparent heterogeneity disappe
ars when taking into account subject-specific risk factors. This test
may also be useful for studying familial aggregation of a disease.