Construct and predictive validity of a self-reported measure of preclinical mobility limitation

Objectives: To validate self-reported preclinical mobility limitation concept and self-report assessment method against muscle power and walking speed, and to study the predictive validity of preclinical mobility limitation with respect to future risk of manifest mobility limitation. Design: Observational prospective cohort study and crosssectional analysis. Setting: Research laboratory and community. Participants: A total of 632 community-living (age range, 75-81y) women and men took part in the baseline assessments and 302 persons in the semi-annual interviews on mobility limitation over 2 years. Interventions: Not applicable. Main Outcome Measures: Walking speed, muscle power, and self-reported preclinical and manifest mobility limitation. Preclinical mobility limitation was defined as self-reported tiredness or modification of task performance without task difficulty. At baseline, 4 subgroups were created according to self-reported preclinical mobility limitation in any of 3 mobility tasks (walking 2km, walking 0.5km, climbing up stairs): no limitation, preclinical limitation, and minor and major manifest limitation. Results: At baseline, participants with preclinical mobility limitation showed intermediate levels of walking speed and muscle power, compared with those with no limitation or manifest mobility limitation. Participants reporting baseline preclinical mobility limitation had 3- to 6-fold higher age- and sex-adjusted risk of progressing to major manifest mobility limitation during the 2-year follow-up compared with participants with no limitation at baseline, whereas the risk among those with minor limitation at baseline was 14- to 18-fold higher compared with those with no limitation. Conclusions: The self-report assessment tool proved to be a valid measure to capture the early signs of disability and may serve as an inexpensive tool for identifying those nondisabled persons at high risk for future disability.