b'CHAPTER 2 | THE AGING BRAINFIGURE 2-4Incidence of dementia subtype by age: 2001-2009 higher level of risk that is greater than simply the Source: Plassman et al. (2011). sum of these two separate risks. Another study leverages the longitudinal nature of ADAMS to Estimate of incidence/1,000Estimate of population Dementia Age person-years (SE) incident cases evaluate the contribution of the genetic marker 72-79 18.9 (4.3) 938,949 to progression of dementia. Interestingly, APOE 80-89 42.2 (7.9) 1,965,362 e 4 predicts cognitive decline over time but not 90+ 82.1 (20.5) 503,009 progression to AD (Brainerd et al. 2013). Another Total 33.3 (4.2) 3,407,320 study creates a genetic risk score for dementia Alzheimers disease (AD) 72-79 16.6 (4.2) 821,592 using other dementia genes and finds that more 80-89 24.2 (4.5) 1,127,323 genetic risk is associated with increased risk of 90+ 64.0 (15.7) 392,057 cognitive decline (Hayden et al. 2015).Cognitive impairmentTotal 22.9 (2.9) 2,340,972 Research using HRS data has actually iden-without dementia 72-79 39.3 (8.2) 1,653,503 tified a new gene that influences memory. Those (CIND) 80-89 73.1 (11.8) 2,538,220 with the gene FASTKD2 perform better on some 90+206.4 (56.1) 630,925 memory tests than those without it. This discovery Dementia Total 60.4 (7.2) 4,822,649 could point the way to new treatments for the (among CIND) 72-79 102.3 (21.8) 741,835 memory impairments caused by AD or other 80-89 123.8 (26.5) 1,474,533 age-related conditions. Although the influence of 90+ 124.6 (35.6) 341,135 FASTKD2 is modest, it is similar to research in Total 120.3 (16.9) 2,557,503 diabetes, cancer and hypertension that uncovered genes with similar effects that led to targets for Risk Factors for DementiaGenetic and Demographic Risk drugs that are now commonly used (Ramanan The HRS and ADAMS are used to identify riskWith a large database of genetic information onet al. 2015). HRS research also supports the idea factors for cognitive impairment and dementia.participants, the HRS is at the forefront of dis- that memory decline is influenced by multiple Studies identify risk factors that may be directlycovery of genetic and medical risks for dementia.genes. Marden et al. (2016) use HRS genetic data modified through intervention and risk groupsResearch using HRS data is beginning to shedto create a polygenic risk score based on the top who may be the focus of intervention. Numerouslight on how genes work to affect dementia.22 AD-associated genes as an alternative to exclu-studies use HRS and ADAMS data to contributeThere is likely no single memory gene, but thesively using APOEe 4. to our understanding of genetic and demographicAPOE gene, specifically thee 4 variant, has beenThe first study of prevalence in the ADAMS risk, including educational level. A range of studieswidely identified as a very significant risk factorpopulation shows, not surprisingly, that age is a investigate medical conditions that may put indi- for cognitive decline. Llewellyn et al. (2010) findpowerful predictor of AD and other dementias. viduals at risk for cognitive decline. A new area ofthat both APOEe 4 and having a stroke increaseAs other studies show, the APOEe 4 allele is also investigation is the impact of behavioral risks. the risk of dementia, but having both creates aassociated with an increased risk of dementia, and a higher level of education is significantly The HRS is at the forefront of discovery of genetic and medical risksprotective. In contrast to other studies, female gender is not a predictor of Alzheimers risk.for dementia. Research using HRS data is now learning more African Americans have an elevated risk, but about how genes work to affect dementia.41'