Yang, Rasmussen, and Friedman (2002) extracted information from the death certificates of 17,897 individuals with Down syndrome who died in the United States between 1983 and 1997. The median age at death increased dramatically, from 25 years in 1983 to 49 years in 1997, or an average of 1.7 years per year studied. In contrast, the median age of the population in general increased only .2 years per year during this same period of time.
While life expectancy for adults with Down syndrome is approaching normal lifespan they typically experience accelerated aging with an increased prevalence of cognitive and functional impairment after the age of 40. Many of these aging conditions are similar to those experienced by geriatric populations including: acquired sensory deficit, impairment in the activities of daily living, cognitive impairment, mood disorders, behavioral symptoms, epilepsy, thyroid problems, osteoporosis and cardiac problems e.g. atrial fibrillation, mitral valve prolapse.
A study by Hithersay R., Startin CM., Hamburg S., Mok KY., et al. (2018) found dementia was associated with mortality in 70% of persons with Down syndrome over 35 years of age. A specific Apolipoprotein E (APOE ε4) gene variant was associated with increased risk for late-onset Alzheimer's disease. Carriers of APOE ε4 had a 7-fold increase risk of death.
CDC. (2001) Racial Disparities in Median Age at Death of Persons With Down Syndrome --- United States, 1968--1997. MMWR 2001. 50(22);463-5.
Hithersay R, Startin CM, Hamburg S, Mok KY, Hardy J, Fisher EMC, Tybulewicz VLJ, Nizetic D, Strydom A. (2018 ) Association of Dementia With Mortality Among Adults With Down Syndrome Older Than 35 Years. Journal of the American Medical Association. 2018 Nov. 19
National Association for Down Syndrome (NADS). Facts About Down Syndrome. Retrieved 9/15/2010. http://www.nads.org/resources/facts-about-down-syndrome/
Yang, Q., Rasmussen, S.A. & Friedman, J.M. (2002) Mortality associated with Downs syndrome in the USA from 1983 to 1997: a population-based study. The Lancet 359: 1019-1025.