Down Syndrome

Down syndrome or trisomy 21 is a chromosomal disorder caused by the presence of all or part of an extra 21^st chromosome. It is usually associated with some impairment of cognitive ability. Physical growth is often affected, as is facial appearance.

The majority of individuals with DS have mild or moderate learning disabilities. A smaller number have severe to profound mental disability. As is the case in most conditions, life expectancy is most affected in those with the most severe disabilities.

A special feature of DS is the development of Alzheimer-like plaques in the brain that generally manifests from about age 40 onwards.⁴ This brain degeneration has been observed in the autopsies of virtually all persons of this age.⁴ It leads to gradual decline in mental and physical function, and the great majority of persons with DS do not survive beyond age 70.

It has been widely reported that life expectancy in DS has increased dramatically over recent decades. This is so, but is due primarily to a dramatic decline in infant and child mortality, especially in children with congenital heart disease. The life expectancy of persons with DS of age 10, say, has only improved by a few years over this period.

Life expectancy in DS depends to some extent on the severity of the cognitive and physical impairment, and more markedly on the presence of congenital heart disease and leukemia (both of which are much more common in DS than in the general population). The most recent research¹ indicates a life expectancy at age 10, say, to age 56. This does not appear to differ significantly for males and females.

The cited study by our group¹ is based on a large population of persons with DS, addresses a wide range of research questions, and reviews a number of previous mortality-related studies. The reader interested in life expectancy in DS may find this article a useful starting point.

References

1. Day SM, Strauss DJ, Shavelle RM, Reynolds RJ (2005). Mortality and causes of death in persons with Down syndrome in California. Developmental Medicine & Child Neurology, 47:171-176.

2. Singer RB, Strauss DJ (1997). Comparative mortality in mentally retarded patients in California, with and without Down's syndrome, 1986-1991. Journal of Insurance Medicine, 29:172-184.

3. Strauss DJ, Eyman RK (1996). Mortality of people with mental retardation in California with and without Down syndrome, 1986-1991. American Journal of Mental Retardation, 100:643-653.

4. Strauss DJ, Zigman WB (1996). Behavioral capabilities and mortality risk in adults with and without Down syndrome. American Journal of Mental Retardation, 101:269-281.

The studies referenced above are available on the articles page.