low score (n = 436). Very high or low N scores were defined as more than 1.5 s.d. from the mean score adjusted to age and sex (on average 2 s.d.), while high and low N scores were between 1 and 1.5 s.d. from the mean score (on average 1.3 s.d.). Data for relative allele score from the 452 574 SNPs from 100 and 500k Affymetrix arrays with minor allele frequencies above 5% were obtained from five replicate arrays used to assess each sample.