Psychometric Properties of a Scale to Assess the Severity of Bathing Disability

Gill TM, Gahbauer EA, Van Ness PH. Psychometric properties of a scale to assess the severity of bathing disability.

Objective

To develop and evaluate the psychometric properties of a new bathing disability scale.

Design

Reliability and validity study.

Setting

General community.

Participants

Two subsets of community-living older persons, selected from an ongoing longitudinal study, who had some degree of bathing disability or were at increased risk for bathing disability, as determined during a comprehensive assessment at 36 (N=199) and 54 (N=213) months, respectively.

Interventions

Not applicable.

Main Outcome Measures

The bathing disability scale was administered at 36, 54, and 72 months, and changes in scores were assessed between 36 and 54 months and 54 and 72 months, respectively, for the 2 subsets of participants. Convergent construct validity was evaluated by comparisons with changes in activity of daily living (ADL) disability, mobility disability, and the Short Physical Performance Battery (SPPB). Discriminative construct validity was determined by comparisons according to age and physical frailty. Responsiveness was evaluated by comparisons between participants who had and had not been hospitalized and, subsequently, by plotting correlations according to the timing of these hospitalizations.

Results

The test-retest reliability was high, with an intraclass correlation coefficient=0.76 (95% confidence interval=0.59−0.94). The internal consistency reliability was excellent with Cronbach α=0.91−0.97. Changes in scores on the bathing disability scale were positively correlated with changes in scores in ADL and mobility disability and inversely correlated with changes in scores on the SPPB. A greater decline in scores was observed among the oldest old and those who were physically frail, but these differences did not consistently achieve statistical significance. The scale was responsive to the occurrence and/or timing of intervening hospitalizations.

Conclusions

The bathing disability scale is reliable, valid, and responsive and may be suitable for use in clinical trials to evaluate the effectiveness of interventions to enhance independent bathing.