Comparing the performance of health status measures for healthy older adults.

OBJECTIVES

The specific goals of the study were to compare three health status measures among older adults for their correlations with similar scales and to examine whether extreme (positive) health states might lead to measurement problems. We also report on practical administration and response problems among older adults.

DESIGN

Eligible and randomly selected health plan enrollees aged 65 and older were sent a baseline survey about their health. A random sample of persons who returned this survey was recruited to participate in the comparative study. Additional questionnaires were completed by mail and telephone interviews. Measures were repeated at a 1-year follow-up mailing.

SETTING

This study was conducted at Group Health Co-operative (GHC) of Puget Sound, a large prepaid health maintenance organization.

PARTICIPANTS

Subjects were 200 of the 283 older adults selected (68.2% response). Mean age was 72.5 years.

MEASUREMENTS

The primary measures were the Sickness Impact Profile (SIP), the Quality of Well-being Scale (QWB), and three scales of the Medical Outcomes Study Short-Form 36 (SF-36). Also included were a stress scale, the Positive Affect Scale, and the Chronic Disease Score (CDS) computed from the automated pharmacy data.

RESULTS

SIP scores showed a very strong skew toward low (good health) scores with a mean of 3.4% (+/- SD 4.4). The QWB scores ranged from .50 to .90 (mean .73 +/- .09). For the MOS SF-36 scales, scores of 100 (good health) were common for both of the physical health scales but not for general health. Analyses showed the SIP, QWB, and MOS SF-36 scales were moderately to strongly correlated with similar measurement scales and with the independent measure of chronic disease and psychosocial health. Scales repeated at 1 year were highly correlated: intraclass correlation coefficients between baseline and 1 year ranged from an r = .51 to .73.

CONCLUSIONS

Our results suggest that the SIP is not a useful tool for rating healthy, community-dwelling older adults. Two MOS SF-36 measures used in this study showed some tendency for "ceiling" measurement effects. The QWB demonstrated an acceptable distribution of scale scores; however, it is the most complex of the three measures to administer. Among the broad range of older adults, no one tool appears to apply to every situation.