Mortality associated with Downʹs syndrome in the USA from 1983 to 1997: a population-based study

Background Downʹs syndrome is the most frequently identified cause of mental retardation, but information about mortality and comorbidity in people with Downʹs syndrome is limited. Methods We used data from US death certificates from 1983 to 1997 to calculate median age at death and standardised mortality odds ratios (SMORs) for common medical disorders in people with Downʹs syndrome. Findings Of 17 897 people reported to have Downʹs syndrome, median age at death increased from 25 years in 1983 to 49 years in 1997, an average increase of 1•7 years per year studied (p<0•0001). Median age at death was significantly lower in black people and people of other races than in white people with Downʹs syndrome. As expected, death certificates with a diagnosis of Downʹs syndrome were more likely to list congenital heart defects (SMOR 29•1, 95% CI 27•8–30•4), dementia (21•2, 19•6–22•7), hypothyroidism (20•3, 18•5–22•3), or leukaemia (1•6, 1•4–1•8) than were those that did not report Downʹs syndrome. By contrast, malignant neoplasms other than leukaemia were listed on death certificates of people with Downʹs syndrome less than one-tenth as often as expected (0•07, 0•06–0•08). A strikingly low SMOR for malignancy was associated with Downʹs syndrome at all ages, in both sexes, and for all common tumour types except leukaemia and testicular cancer. Interpretation Identification of factors responsible for the racial differences recorded could facilitate further improvement in survival of people with Downʹs syndrome. Reduced exposure to environmental factors that contribute to cancer risk, tumour-suppressor genes on chromosome 21, or a slower rate of replication or higher likelihood of apoptosis in Downʹs syndrome cells, could be possible reasons for paucity of cancer in people with Downʹs syndrome.