Apoliprotein E, type epsilon 4 allele (ApoE-epsilon 4) is associated with late-onset sporadic Alzheimer's disease (AD). We have found that the cumulative probability of remaining unaffected over time decreases for each dose of ApoE-epsilon 4 in sporadic, late-onset French AD. The effect of genotypes on age at onset of AD was analyzed using the product limit method, to compare unaffected groups during aging.