Development and validation of the mobility in middle-age questionnaire

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 7-step Delphi process, consisting of 10 experts, involving item selection and content validation in both English and Hebrew, comprising 2 factors: (1) Current Mobility Ability and (2) 1-Year Mobility Change. Psychometric properties were assessed in 610 US 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 = .94 English; .92 Hebrew) and strong test-retest reliability (intraclass correlation coefficient = 0.89-0.90). Exploratory factor analysis explained 66% of variance; confirmatory factor analysis showed good fit (Comparative Fit Index = 0.99, Tucker-Lewis Index = 0.99, Standardized Root Mean Square Residual = 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 United States; 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.