The Development of the de Morton Mobility Index (DEMMI) in an independent sample of older acute medical patients:...

Area of Science:

• Gerontology and Geriatric Medicine
• Rehabilitation Science
• Health Measurement and Psychometrics

Background:

• Accurate assessment of mobility is crucial for older adults in acute care settings.
• Existing mobility instruments may lack robust psychometric properties for this population.
• The Delftse Measure of the Mobility of the Elderly (DEMMI) was previously developed but required further validation.

Purpose of the Study:

• To refine and validate the 17-item DEMMI in an independent sample of older acute medical patients.
• To confirm the psychometric properties of the DEMMI using Rasch analysis.
• To establish a reliable and valid instrument for measuring mobility in hospitalized older adults.

Main Methods:

• Instrument refinement using Rasch analysis and expert input.
• Validation in a sample of 106 older general medical patients, with 312 mobility assessments.
• Evaluation of measurement properties, including unidimensionality and differential item functioning.

Main Results:

• The 17-item DEMMI was further refined by removing 2 items, resulting in a 15-item instrument.
• The refined 15-item DEMMI demonstrated consistent Rasch measurement properties.
• An interval-level scoring system was established, with no differential item functioning identified.

Conclusions:

• The 15-item DEMMI is a unidimensional, valid, and reliable instrument for measuring mobility in hospitalized older acute medical patients.
• This study confirms the DEMMI's suitability for monitoring mobility changes in this population.
• The DEMMI is the first mobility instrument for older people developed, refined, and validated using the Rasch model.