Preclinical mobility disability predicts incident mobility disability in older women

Background, Physical disability and dependency are serious, and frequent, a dverse health outcomes associated with aging and resulting from chronic dis ease. Reasoning has suggested that there might be a preclinical, intermedia te phase of disablement which might develop in parallel with progression of underlying disease and precede and predict disability. Definition of this stage could provide a basis for screening and early intervention to prevent disability. The objective of this study was to de termine preclinical func tional predictors of incident mobility difficulty and provide evidence for a preclinical stage of disability. Methods, A prospective, population-based cohort study was carried out in Ba ltimore, Maryland, with two evaluations 18 months apart. The participants w ere 436 community-dwelling women, 70-80 years of age at baseline, not cogni tively impaired, and reporting difficulty in no areas, or only one area, of physical function (primarily mobility), who were participating in the Wome n's Health and Aging Study II. Participants were recruited from a populatio n-based, age-stratified random sample. Incident mobility disability was stu died in the subset without such disability at baseline. The main outcome me asure was self-reported incident difficulty walking 1/2 mile or climbing up 10 steps. Results. At baseline, 69.3% of the cohort reported no difficulty with mobil ity. After 18 months, 16.0 and 11.7% of this group reported incident diffic ulty walking 1/2 mile or climbing up 10 steps, respectively. Those reportin g baseline task modification due to underlying health problems, our measure of preclinical disability, were at three- to fourfold higher odds of progr essing to difficulty than were those without such modification. In multivar iate logistic regression analyses, this self-report measure, task modificat ion without difficulty and objective measures of performance were independe ntly and jointly predictive of incident mobility difficulty. Specifically, for incident difficulty walking 1/2 mile, self-reported task modification o dds ratio (OR) = 3.67, walking speed (.5 mis difference) OR = 2.16; for inc ident difficulty climbing up 10 stairs, OR for task modification = 3.84, fo r stair climb speed (1/3 step/s difference) = 2.08 (95% CI did not include 1 for any). Covariates, age, living alone, number of chronic diseases, depr ession score, knee strength, and balance by functional reach, were not sign ificant predictors in either model. Conclusions. Two indicators of functional changes in older women without mo bility difficulty, self-report of modification of method of doing a task in rile absence of difficulty and performance measures, are independent and s trong predictors of risk of incident mobility disability. The self-report m easure provides substantial strength in predicting risk of incident disabil ity across the full range of performance, and may identify a vulnerable poi nt at which other risk factors act to cause transitions to disability. Toge ther, the preclinical indicators identify a subset of high-functioning olde r women who are at high risk of mobility disability, and provide a potentia l basis for screening for disability risk and targeting interventions to pr event mobility disability.