The Relationship between Disease and Function and Perceived Health in Very Frail Elders

OBJECTIVE: To study associations between disease and observed function and self-perceived health in very frail elders. DESIGN AND SETTING: Cross-sectional survey of nine nursing homes in San Antonio, TX. PARTICIPANTS: 194 elderly long-stay nursing home residents dependent in at least two ADLs and without severe cognitive impairment. MEASURES: Burden of disease (BOD) was chart abstracted using a standardized protocol that assessed types and severities of 59 categorizations of chronic and acute medical conditions. Observed function and self-perceived health status were assessed independently by the Katz Activities of Daily Living scale (ADL) and the Sickness Impact Profile (SIP), respectively. RESULTS: Summary BOD scores had a low, but statistically significant, univariate correlation with ADL scores (r = 0.21, P = 0.003) and no significant correlation with SIP scores (R = -0.008). Multiple linear regression analyses, including the 24 most frequent disease categories, showed that disease explained significant amounts of ADL (r2 = 0.25, P = 0.001) and borderline significant amounts of SIP (r2 = 0.16, P = 0.11). Models including both disease and sociodemographic, cognitive, and affective variables showed disease added significant incremental explantation beyond the other factors to ADL (incremental r2 = 0.14, P = 0.04), but not to SIP (incremental r2 = 0.08, P > 0.10). CONCLUSIONS: Disease, observed function, and self-perceived health status are separate, but interrelated entities, with disease having a stronger relationship to observed function than self-perceived health. Comprehensive assessment of frail elders may need to include all three areas, and studies that focus on one area should take into account the other two as potential important covariates.