Refining the categorization of physical functional status: the added value of combining self-reported and performance-based measures.

BACKGROUND: When considered individually, self-reported functional status and performance-based functional status predict functional status decline and mortality. However, what additional prognostic information is gained by combining these approaches remains unknown.
METHODS: The authors used three waves of three sites (5138 participants) of the Established Populations for Epidemiologic Studies of the Elderly to determine the prognostic value of individual and combined approaches. Baseline self-reported (mobility and activities of daily living [ADL] items) and performance-based (Physical Performance Score) functional status information was classified into three and four hierarchical categories, respectively.
RESULTS: Based on self-reported information alone, at 1 year, 73% participants had not changed, 15% declined, 6% improved, and 6% died. At 4 years, 53% had not changed, 24% declined, 2% improved, and 22% died. Based on performance-based assessment alone, at 4 years, 33% of the sample remained stable, 37% declined, 6% improved, and 24% died. In the top two self-reported categories, functioning on the performance-based assessment varied widely. Among those who were independent in all self-reported functioning, approximately 40% scored in each of the top two performance-based categories. Among persons in the top two self-reported categories, poorer performance was associated with progressively higher 1-year and 4-year mortality rates. Among persons with impaired mobility and at least 1 ADL dependency, the mortality rate was high and was not influenced by performance-based score.
CONCLUSIONS: Combining self-reported and performance-based measurements can refine prognostic information, particularly among older persons with high self-reported functioning. However, if ADL dependency is present, performance-based measures do not add prognostic value regarding mortality.