Table 1 Polymorphisms from the IIS pathway selected on the basis of previously described functionality and their expected effect on IIS activity.

For the sex-stratified mortality analyses, we used left-censored Cox regression to calculate proportional hazard ratios, as subjects from the cohort ’87 entered the risk set at a different age (Kurtzke, 1989). For cohort ’87, the age of entry varied between 85 years and 103 years, whereas for cohort ’97, the age of entry was 85 years for all subjects. Because low variant allele frequencies resulted in a very small group size of homozygous variant allele carriers, we combined heterozygous and homozygous variant allele carriers to increase the power to detect dominant effects. The hazard ratio indicates the rela- tive mortality risk of variant allele carriers vs. the homozygous wild-type allele carriers, the latter being the reference group.

Table 2 Polymorphisms from the oxidative stress response selected on the basis of previously described functionality and their expected effect on the oxidative stress response pathway.

Acknowledgments

We are grateful to J. J. Houwing-Duistermaat for the use of multivariate analysis. We thank all other members the Long Life study group: A. Ayrinhac, E. A. Baldal, G. J. D. I. Boomsma, P. M. Brakefield, R. Bijlsma, J. C. van ingen, D. L. Knook, I. Meulenbelt, P. H. E. M. de Meijer, J. L. P. W. G. M. van de Zande. We thank C. de M. van Schie and M. van Kersbergen-van Oostrom for assistance. We are grateful to Gerrit van der Steege and Bruinenberg for use of their ABI7900 Taqman equipment Groningen. This work was funded by an IOP (Innovative Research) grant from the Dutch Ministry of Economic (grant number IGE01014).

To test for combined effects of the selected polymorphisms, a composite (sub)pathway score was calculated for each par- ticipant by assigning a score of +1 for carriership of a variant causing increased signalling and a score of −1 for carriership of each variant causing decreased signalling. Alternatively, the poly- morphisms belonging to the same (sub)pathway (IIS pathway or oxidative stress response) were tested simultaneously as inde- pendent covariates in the above-mentioned models. We used multivariate analyses to adjust for the effects of the other func- tional variants from the same pathway. SPSS and STATA were used for the statistical analyses and Thesias was used for cal- culation of linkage disequilibrium between the two polymor- phisms in IGF1 and the two polymorphisms in UCP2.

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