Measuring higher level physical function in well-functioning older adults:Expanding familiar approaches in the health ABC study

Background. To evaluate development and progression of functional limitatio n and retain comparability with established approaches, we raised the measu rement ceiling of commonly used self-report and performance-based measures of function. This study evaluated the utility and concurrent validity of th ese expanded measures. Methods. The study population consisted of 3075 black and white men and wom en aged 70 to 79 years, with no reported mobility limitations or disability , participating in the Health, Aging, and Body Composition, or Health ABC s tudy. Self-report measures were expanded by ascertaining case of performanc e and including more demanding levels of some tasks. A single foot stand an d narrow walk supplemented an established performance battery. For walking endurance, we developed the Long Distance Corridor Walk (LDCW), which inclu des distance covered in 2 minutes and the time to walk 400 m. Results. The expanded self-report items identified one half of the men and one third of the women as exceptionally well functioning and 10% to 13% of men and 21% to 36% of women with lower capacity. The supplemented and re-sc ored performance battery discriminated function over the full range. The LD CW further differentiated walking capacity at the high end and also identif ied a subgroup with limitations. The self-report and performance measures w ere significantly, but weakly, correlated (0.13-0.35) and were independent predictors of walking endurance. Conclusions. Well-functioning persons in their 70s exhibit a broad range of functional capacity readily ascertained by expanded self-report and perfor mance tests, Significant associations among these measures support their co ncurrent validity, but generally weak correlations indicate they tap differ ent, but important, dimensions of physical function.