Date Published: April 18, 2019
Publisher: Public Library of Science
Author(s): Li Zhang, Linwen Guo, Huitao Wu, Xiaowen Gong, Junqi Lv, Yanfang Yang, Bruno Pereira Nunes.
Functional disability is a common health burden in older adults and follows a hierarchical pattern. Physical performance measures are useful for the objective estimation of functional disability. This study primarily aimed to compare the validity of handgrip strength and gait speed, alone and in combination, for recognizing the functional disability among Chinese older adults. This study also aimed to stratify the functional disability according to the criterion-referenced values of handgrip strength and gait speed.
We selected 6127 respondents from the 2011 wave of the China Health and Retirement Longitudinal Study. Here, we defined functional disability as needing any help in any items of activities of daily living (ADL) and instrumental activities of daily living (IADL). To assess the validity of physical performance measures alone and in combination for the recognition of functional disability, we conducted the receiver operating characteristic analysis.
Compared with handgrip strength, the gait speed could better discriminate ADL disability and showed a satisfactory discriminant validity (area under the curve ≥ 0.7) in men. However, this finding was not found in the recognition of IADL disability. When combining these two measures, the parallel test showed a high sensitivity with a poor specificity, whereas the serial test showed a perfect specificity with a poor sensitivity.
We developed the hierarchical cut-off values of handgrip strength and gait speed for identifying and stratifying the functional disability among Chinese adults over 60 years old. The speed test was superior to handgrip strength in identifying ADL disability. The parallel tests of those with high sensitivity perhaps could help identify the functional disability. Further work on cost-utility analysis is warranted.
Functional disability, defined as a dependency in activities of daily living (ADL) and/or instrumental activities of daily living (IADL), is a significant and profound health outcome for older adults [1–4]. Functional disability is associated with future falls, cognitive decline, hospitalization, and mortality . IADL are related to functioning independently in a given environment, whereas ADL are essential for self-care in routine activities [4–6]. In most older adults, functional disability presents a hierarchical pattern. They first encounter difficulty in performing IADL, followed by ADL [7–8]. ADL disability represents a relative severity stage in the disablement process. Functional disability can indicate the intrinsic capacity of older adults . Many individuals experience periods of high and stable capacity, declining capacity (they may encounter IADL disability), and a significant loss of capacity (they may experience ADL disability). Interventions may have to be tailored depending on the presence and stage of intrinsic capacity. Therefore, stratifying older people according to the stage of intrinsic capacity trajectory (or functional disability) would likely facilitate the intervention programs to optimize the intrinsic capacity trajectory and achieve the goal of healthy aging. Thus, a valid, simple, and reliable tool for identifying high-risk disability population is critical, particularly in a health care program.
In this study, we developed the criterion-referenced values of handgrip strength and gait speed for functional disability. Additionally, we validated the significantly positive association between poor physical performances with ADL and IADL disabilities by logistic regression model. On these bases, we compared the validity of the combined tests of handgrip strength and gait speed. The parallel test showed a high sensitivity with a poor specificity, whereas the serial tests showed a perfect specificity with a poor sensitivity.
We developed the cut-off points of handgrip strength and gait speed for the stratification of functional disability in older adults. Furthermore, after comparing the validity of their cut-off points, we found that the gait speed was superior to handgrip strength for identifying ADL disability. Based on the goals of interventions for high-risk group, the performance of parallel tests with high sensitivity was more preferable than serial tests. Nonetheless, further cost-utility analysis is necessary. Overall, the physical performance measures could provide additional information about the physical function of older adults to help clinicians identify the high-risk groups with functional disability and guide the targeted interventions.