This is a brief review of:
Eyman RK, Grossman HJ, Chaney RH, Call TL. The life expectancy of profoundly handicapped people with mental retardation. N Engl J Med. 1990 Aug 30;323(9):584-9.
Note: This review was revised on 25 May 2018 to correct an outdated url for the book Damages by Barry Werth.
This study was groundbreaking in many ways, and cemented the notion that survival of children with neurological disabilities, including children with cerebral palsy, is strongly associated with level of independent gross and fine motor functioning, feeding skills, and cognitive abilities. More mobile and functional children have longer life expectancies, and the most severely disabled children have dramatically shorter life expectancies.
Unfortunately, a serious arithmetical error in this study falsely inflated the reported estimates of mortality rates, and the reported life expectancies were consequently lower than they should have been. This unfortunate error made its way into a number of court cases, where Dr Grossman himself periodically testified as to the life expectancy of children with cerebral palsy based on results reported in this study. One notable case was documented in the book Damages by Barry Werth.
In a later study by some of the same authors, the arithmetic error was corrected, but a methodological error was introduced. Groups were formed according to levels of functional ability, but children who improved (or declined) from a given level of functioning were removed from the analyses of survival going forward. As children who lived longer were more likely to change levels, this methodological error (or choice, if error is too strong a word) likely introduced a bias toward shorter survival.
In spite of the errors in these early studies by Eyman and Grossman and others, the main message was consistent and correct, as has been demonstrated in a number of more methodologically sound studies since: levels of independent gross and fine motor skills, feeding skills, and (to a lesser degree) cognitive abilities are strongly associated with mortality rates and life expectancies of children with cerebral palsy and other neurological or developmental disabilities.