The effect of Alzheimer's disease-associated genetic variants on longevity

Abstract

The genetics underlying human longevity is influenced by the genetic risk to develop -or escape- age-related diseases. As Alzheimers disease (AD) represents one of the most common conditions at old age, an interplay between genetic factors for AD and longevity is expected. We explored this interplay by studying the prevalence of 38 AD-associated single-nucleotide-polymorphisms (SNPs) identified in AD-GWAS, in self-reported cognitively healthy centenarians, and we replicated findings in the largest GWAS on parental-longevity. We found that 28/38 SNPs identified to associate with increased AD-risk also associated with decreased odds of longevity. For each SNP, we express the imbalance between AD- and longevity-risk as an effect-size distribution. When grouping the SNPs based on these distributions, we found three groups: 17 variants increased AD-risk more than they decreased the risk of longevity (AD-group): these variants were functionally enriched for {beta}-amyloid metabolism and immune signaling, and they were enriched in microglia. 11 variants reported a larger effect on longevity as compared to their AD-effect (Longevity-group): these variants were enriched for endocytosis/immune signaling, and at the cell-type level were enriched in microglia and endothelial cells. Next to AD, these variants were previously associated with other aging-related diseases, including cardiovascular and autoimmune diseases, and cancer. Unexpectedly, 10 variants associated with an increased risk of both AD and longevity (Unexpected-group). The effect of the SNPs in AD- and Longevity-groups replicated in the largest GWAS on parental-longevity, while the effects on longevity of the SNPs in the Unexpected-group could not be replicated, suggesting that these effects may not be robust across different studies. Our study shows that some AD-associated variants negatively affect longevity primarily by their increased risk of AD, while other variants negatively affect longevity through an increased risk of multiple age-related diseases, including AD.