These odds ratios are not constant across human populations and even vary by ethnicity,or circumstances, so some caution is needed when extrapolating them to new data; but as AD GWASdata accumulate, over 20 common genetic variants have been found to affect AD risk — 3of them, in the genes CLU, PICALM, and CR1, appear to beassociated with a difference in disease risk of over 10% per allele. This evidence concerns the gene CLU and Alzheimer disease.