The HWE (Hardy Weinberg equilibrium) test and linkage disequilibrium test were performed using Genepop 3.4 software (Raymond and Rousset, 1995) and Haploview software (Barrett et al., 2005). Several studies have been conducted on the association between these three SNPs and cancers. In 2006, a study showed that homozygosity of the minor allele of 1246C/T (rs35767) was associated with a reduction in the risk of breast cancer and a significant decrease in circulating IGFBP3 levels in elderly Caucasian women (Canzian et al., 2006). Another study suggested that there was a 30% reduction in the risk of colorectal cancer associated with possession of one or two copies of the C allele compared with TT genotype of 541T/C (rs5742612) in a Singapore Chinese population (Wong et al., 2005). Meanwhile, Iona Cheng et al. found that a haplotype block, which embraced the promoter area, was associated with prostate cancer and that the SNP 439T/A (rs2288377) was associated with prostate cancer, mainly due to linkage disequilibrium (Cheng et al., 2006). Although longevity people are generally free of lethal age-related cancers (Bonafe et al., 2002), we could not find any association between the three SNPs and longevity in our study. The primary reason might be the complicated relationship between cancers and longevity (Campisi, 2003), which can abate the effect of genetic association studies. Different ethnic populations, sample sizes, and living circumstances for people in these studies can also be another reason. The last but not least, the intricate Insulin/IGF-1 signal pathway in the aging process cannot be excluded. It has been reported that a composite score of selective variants in several Insulin/IGF-1 signal pathway genes was associated with height and longevity (van Heemst et al., 2005). That is to say, the variants in IGF-1 promoter region may work in tandem with variants in other genes in this pathway, which cannot be shown in an association study that only includes this region.

Our study does not support the association between SNPs in the promoter region of the IGF-1 gene and longevity in the Han Chinese population. It is just a primary and explorative step to explore the possible function of this region in human longevity. Studies based on a larger subject group and longer potential sequence segments in this region and other genes are required to test our results.

We are grateful to the individuals who participated in this research. Additionally, we thank Dr. Hui Li, Dr. Chengye Wang, and Kristen Choffe for their help in preparing the paper. This work was supported by National Basic Research Program of China (No. 2007CB507405), Light in Western China of the Chinese Academy of Sciences, the National Natural Science Foundation of China (No. 30621092), and Bureau of Science and Technology of Yunnan Province.

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