HOW MEASUREMENT TECHNIQUES INFLUENCE ESTIMATES OF DISABILITY IN OLDERPOPULATIONS

Measures of disability in activities of daily living (ADL) have become important indicators of the health of older persons. One fundamental decision in disability research is constructing or choosing a rating s cale to measure ADL disability. Although there is growing consensus in the field on what ADLs to measure, there is little agreement on how t o measure ADL disability. This study compares the effect of scales tha t rate the presence of difficulty, use or human assistance and use of any type of assistance to perform seven different ADLs on prevalence e stimates of disability in a probability sample of 1818 adults 70 years of age and older living in the six New England states. Results reveal that different disability rating scales can have a dramatic impact on prevalence estimates of disability in older populations. Measures tha t used the 'difficulty' scale produced disability estimates from 1.2 t o 5 times greater than estimates from the 'human assistance' scale. Th e effect of rating scales was associated with respondents' age, social factors, and health status. Effects also varied substantially across different ADLs. Researchers need to make careful choices of the disabi lity ratings scales and use caution in drawing inter-study comparisons where different scaling methods were employed.