Mortality in adults with moderate to profound intellectual disability: a population-based study.

BACKGROUND: People with intellectual disability (ID) experience a variety of health inequalities compared with the general population including higher mortality rates. This is the first UK population-based study to measure the extent of excess mortality in people with ID compared with the general population.
METHOD: Indirectly standardized all-cause and disease mortality ratios (SMRs) and exact Poisson confidence intervals were calculated by age and sex for all adults, aged 20 years or over, with moderate to profound ID living in Leicestershire and Rutland, UK, between 1993 and 2005. The general population of Leicestershire and Rutland, which has a population of approximately 700,000 individuals in this age range, was used for comparison. To explore differences within the study population, overall SMRs were also calculated by presence of Down syndrome and last place of residence (city or county).
RESULTS: Of 2436 adults identified, 409 (17%) died during 23,000 person-years of follow-up. Both all-cause and disease-specific mortality were around three times higher than the general population but varied considerably with age. The largest differences were observed in people in their twenties, where all-cause mortality was almost nine times higher in men (SMR=883; 95% CI=560-1325) and more than 17 times higher in women (SMR=1722; 95% CI=964-2840). At a particular disadvantage were people with Down syndrome and women with ID living in the city.
CONCLUSIONS: The relatively high SMRs observed in young people and in women, particularly those living in inner city areas and with Down syndrome, deserve further investigation for possible explanations, including socio-economic factors.