Bias in proxies' reports of disability: Data from the national health interview survey on disability

Objectives. These studies examined whether differences between self-reports and proxy reports of disabilities reflect proxy response biases or only re spondent selection factors. Methods. The data were from the National Health Interview Survey on Disabil ity (1994-1995, phases 1 and 2). In study 1, reports of disabilities were r egressed on respondent status, self vs proxy, and demographic factors. In s tudy 2, the ratios of the proportions of self-reports and proxy reports of disabilities were regressed on independent lay ratings of observability of these disabilities and their "interactional" nature. In study 3, the disabi lity reports for people who differed in respondent status in one phase but self-reported the same disability in the other phase were compared. Results. In study 1, proxies underreported disabilities for people aged 18 to 64 years but overreported for people 65 years or older. In study 2, the observability and interactional scores accounted for more than 60% of the v ariance of self and proxy differences in an inverse relationship. study 3 c onfirmed the basic findings of study 1. Conclusions. Use of proxies in representative surveys on disability introdu ces systematic biases, affecting national disability estimates.