The dynamic nature of mobility disability in older persons.

OBJECTIVES: To determine the rates of clinically meaningful transitions in mobility disability; evaluate how these transitions differ according to age, sex, and physical frailty; and depict the duration of the resulting episodes of mobility disability.
DESIGN: Prospective cohort study.
SETTING: General community in greater New Haven, Connecticut, from March 1998 to October 2004. PARTICIPANTS: Seven hundred fifty-four community-living older persons, aged 70 and older, who were nondisabled (i.e., required no personal assistance) in four activities of daily living. MEASUREMENTS: Mobility disability, defined as the inability to walk one quarter of a mile and to climb a flight of stairs, respectively without personal assistance, was assessed every month for up to 5 years.
RESULTS: For both mobility tasks, rates per 1,000 person-months were higher for transitions from no disability to intermittent disability (34.7 for walking one quarter of a mile and 17.4 for climbing a flight of stairs), intermittent to continuous disability (52.0 and 42.5), continuous to intermittent disability (35.4 and 31.5), and intermittent to no disability (68.6 and 85.4) than for other transitions. Older age, female sex, and physical frailty were associated with greater likelihood of transition to states of greater disability and lower likelihood of regaining independent mobility.
CONCLUSION: Mobility disability in older persons is a highly dynamic process, characterized by frequent transitions between states of independence and disability. Programs designed to enhance independent mobility should focus not only on the prevention of mobility disability but also on the restoration and maintenance of independent mobility in older persons who become disabled.