Our SNPs were chosen using information from HapMap, but one study which re-sequenced longevity candidates (including FRAP1) in healthy old adults showed that only 19% of variants in their sequencing set were observed in HapMap [39]. It is possible, then, that we are missing important uncommon variants that do have effects on the longevity-related traits of personality and psychological distress. While it is possible that other genes or other factors may influences the relationship between personality and longevity, we can fairly confidently rule out common variants in the AFG3L2, FRAP1, MAT1A, MAT2A, and SYNJ1 genes. Follow-up of further variants in SYNJ2, and especially in older cohorts, is needed before we can dismiss it as a candidate gene for personality and psychological distress in old-age. Genome-wide association studies of both of longevity and personality [40, 29] will serve as important repositories of gene associations that can be interrogated systematically for longevity candidate genes, such as SYNJ2. Furthermore, strategies focussed on rare variants in longevity candidate genes could prove a fruitful approach.
