Since GWAS-identified SNPs have a relatively low predictive value for disease risk (24-26), we expected that these risk alleles would only marginally affect population-wide survival. However, the cumulative effect of cardiovascular disease, cancer, and type 2 diabetes risk alleles did not affect population survival, despite being expected to be more pronounced (9,10). Whether disease risk attributable to the cumulative effects of susceptibility alleles is associated with population-based mortality risk should be tested in patient-based studies. Alternatively, other genetic and environmental factors present in individuals surviving into old age may counteract the detrimental effects of disease susceptibility alleles.

Genotyping of the selected SNPs was performed using the Sequenom MassARRAY iPLEXGold platform. The average genotype call rate for genotyped SNPs was 96.3%, and the average concordance rate was 99.7% among 4% duplicated control samples. All 30 SNPs were in Hardy-Weinberg equilibrium (P < 0.002) among the controls.

We applied a variance-modified Cochrane-Armitage test in single-SNP analysis meta-analysis to take into account the relatedness between highly aged sibling cases when computing the variances of the scores (29). In the meta-analysis of both the LLS and Leiden 85 Plus Study/NTR controls, the score statistics of the two studies were combined using a fixed-effects approach. For each individual who was genotyped for all 30 SNPs, we counted the total number of disease risk alleles in cumulative SNP analysis. The difference in the number of disease risk alleles between long-lived subjects and population controls was assessed by linear regression.

All participants of the LLS, Leiden 85 Plus Study, and NTR provided written informed consent after receiving an explanation of the nature and consequences of the study. Nonagenarian siblings of European descent were recruited for the LLS, together with their offspring and partners of their offspring, who served as population controls. Families were recruited if at least two long-lived siblings were alive and fulfilled age criteria: 89 years or older for men and 91 years or older for women, representing less than 0.5% of the Dutch population in 2001 (1). In total, 944 long-lived proband siblings with a mean age of 94 years (range: 89-104 years), 1,671 offspring with a mean age of 60 years (range: 39-81 years), and 744 partners with a mean age of 60 years (range: 36-79 years) were included.

We used polychotomous regression (31) and logic regression (32) to identify subsets of SNPs that might have a joint effect on longevity in the datasets of the LLS and Leiden 85 Plus/NTR controls. Cross-validation was used for selecting the best subset of SNPs and the best functional forms of those subsets. The polychotomous regression is flexible in terms of inheritance modes of the SNPs, although only pairwise interactions are considered, whereas the logic regression is used to identify multiple interacting dominant and recessive effects of SNPs.

We thank all participants of the Leiden Longevity Study, Leiden 85 Plus Study, and Netherlands Twin Register. This study was supported by a grant from the Innovation Oriented Research Program on Genomics (SenterNovem IGE05007), the Centre for Medical Systems Biology, and the National Institute for Healthy Ageing (Grant 05060810), all in the framework of the Netherlands Genomics Initiative/Netherlands Organization for Scientific Research. The data collection of the Netherlands Twin