Indexed on: 23 Mar '17Published on: 23 Mar '17Published in: The journals of gerontology. Series A, Biological sciences and medical sciences
By including categories for accommodations and reduced frequency, to supplement earlier classifications of difficulty and dependence, a new 5-category functional scale has the potential to distinguish finer gradations in disability but the hierarchical nature and advantages of this scale over alternative scales are uncertain.Using data from the National Health and Aging Trends Study (N = 7,609), we conducted a series of: cross-sectional analyses that focused on the hierarchical consistency of responses in the 5-category scale; and longitudinal analyses that focused on predictive accuracy for mortality and functional dependence, comparing the 5-category scale with three simpler scales, having only three or four categories.Although there was considerable variability across the seven functional activities, the prevalence of inconsistencies in the hierarchy of the 5-category scale (eg, reports difficulty but no accommodations) was relatively high. In addition, the predictive accuracy of the 5-category scale for mortality and functional dependence was only modestly better than that of the two 3-category scales and was comparable to that of the 4-category scale. Finally, when evaluated as summative disability scores, there was little difference in predictive accuracy between the 5-category scale and three alternative scales.Despite inconsistencies in its hierarchy, the 5-category scale is more effective in stratifying risk for mortality and functional dependence than the two 3-category scales but not the 4-category scale. When assessing changes over time, however, the addition of questions on accommodations and reduced frequency to those on difficulty and dependence, to form a summative disability score, offers little benefit and increases the burden of the assessment.