The association of FOXO with diverse aging phenotypes, including insulin sensitivity, CHD, cancer, type 2 diabetes, and longevity is suggestive of a gatekeeper role in the IIS pathway. An important downstream mechanism whereby FOXO3A might influence humanRevealed no differences in education and occupation (data not shown) between cases and controls. Moreover, it was the participants who were older at baseline who were more likely to have lived to 95-plus years and thus obtain the longevity phenotype. Most cohort effects show health advantages for younger cohorts. However, it is interesting to note that in C. elegans, several genes that by themselves may have small effects on lifespan are influenced by the transcription regulating master gene DAF-16 (59). Small differences in FOXO3A that may be otherwise difficult to detect could theoretically modify several downstream genes related to DNA binding, protein-protein interactions, cell cycle progression, apoptosis, and metabolism. In this manner, a small modifying effect by FOXO3A potentially has larger additive downstream effects on aging phenotypes and longevity. In summary, we found that common, natural genetic variation within the FOXO3A gene was strongly associated with human longevity and was also associated with several phenotypes of healthy aging. Further study of FOXO genes and aging phenotypes is warranted in other populations. Supportive evidence is beginning to accumulate for a role of insulin-signaling in human aging and longevity, but the genes that might mediate these effects are not known. Prior studies have found over or under-representation of single nucleotide polymorphisms (SNPs) from the insulin-IGF-1 signaling pathway in long-lived humans of Italian (36), Japanese (37, 42), Dutch (60), and Ashkenazi Jewish (38) ethnicity, with links to several aging phenotypes. While some of these findings have been limited by small effect sizes and marginal statistical significance, the study by Suh et al. (38) also demonstrated that functionally significant mutations in the IGF-1 pathway confer longevity.
 
Subjects and Methods
 
Study Population:
 
This nested case-control study was conducted as part of the Hawaii Lifespan Study, an embedded cohort study of healthy aging drawn from the original population of the Honolulu Heart Program (HHP) and Honolulu Asia Aging Study (HAAS). The HHP is a population-based, prospective study of cardiovascular disease among 8006 Japanese-American men that began in 1965. The HHP participants were recruited from 9877 men with valid contact information who were born from 1900-1919 and living on the island of Oahu (61). Study participants had both parents from Japan, usually the west and southern parts of Japan (61, 62). Although most participants were born in Hawaii (88%), there is a theoretical possibility of confounding of case-control status with allele frequencies due to geographic origin. Therefore, for certain analyses, cases and controls were stratified by parental prefecture of origin using conditional logistic regression models. Analyses showed no evidence for population stratification in the dataset (data not shown). The HHP cohort has been described elsewhere (62). Briefly, surveillance of hospital records, obituaries, and national databases has resulted in extensive morbidity and mortality data (adjudicated by an expert committee) and near-complete follow-up (61-63).
 
To date, there has been little study of FOXO genes and phenotypes of aging in humans. Two recent studies suggest that FOXO genes deserve further scrutiny. First, a longitudinal study of elderly Dutch men and women found that a FOXO1A haplotype predicted 4-year survival and that a FOXO3A haplotype predicted stroke risk (39). Second, the Framingham Study, in a genome-wide association analysis, found that a FOXO3A SNP was strongly associated with age at natural menopause in women (P = 0.00003). However, the Dutch findings were not statistically significant when accounting for multiple comparisons and both studies need replication. The present study is supportive and extends the associations of FOXO3A to human longevity and insulin sensitivity.
 
All participants for the current study were drawn from records of study participants updated to August 2007. Archived phenotypic data and blood samples from Examination 4 of the HHP (1991-1993), which coincided with the commencement of the Honolulu Asia Aging Study (HAAS), were used as the baseline examination for this nested case-control study. The HAAS was begun as an expansion of the HHP for the study of neurodegenerative diseases, cognitive function, and other aging phenotypes in elderly persons (64). Participants included 3741 men aged 71 to 93 at Examination 4 (mean age 77.9 ± 4.7 years), approximately half the number of the original HHP (64).