Development and Validation of the Mobility in Middle-Age Questionnaire (MMQ).

BACKGROUND Mobility decline often begins in midlife and early identification of individuals at risk of accelerated deterioration can enable timely prevention. However, there is no validated self-report instrument that specifically assesses mobility in the middle-aged population. METHODS The Mobility in Middle-Age Questionnaire (MMQ) was developed through a seven-step Delphi process, consisting of 10 experts, involving item selection and content validation in both English and Hebrew, comprising two factors: (1) Current Mobility Ability and (2) One-Year Mobility Change. Psychometric properties were assessed in 610 U.S. and 594 Israeli middle-aged adults. Analyses included internal consistency, test-retest reliability, structural and construct validity (using the 10-item Physical Functioning scale (PF-10) from SF-36), and floor/ceiling effect assessments. A 'Potential Mobility Risk Zone' was defined as the lowest 20% of MMQ scores. RESULTS The MMQ showed excellent internal consistency (Cronbach's α  =  0.94 English; 0.92 Hebrew) and strong test-retest reliability (ICC = 0.89-0.90). Exploratory factor analysis explained 66% of variance; confirmatory factor analysis showed good fit (CFI = 0.99, TLI = 0.99, SRMR = 0.05). Construct validity was supported, with all pre-defined hypotheses confirmed. MMQ showed significantly lower ceiling effects than PF-10 (3.9% vs. 34.5% in U.S.; 0.17% vs. 25.25% in Israel, p < .001, large effect sizes). A score of 50 (20th percentile) was proposed as a preliminary "Potential Mobility Risk" Threshold. CONCLUSIONS The MMQ is a reliable and valid tool for detecting early mobility decline in midlife. Longitudinal studies are needed to confirm its predictive value and responsiveness to change.