Establishing a Hierarchy for the Two Components of Restricted Activity

Increasing evidence suggests that illnesses and injuries leading to restricted activity have adverse functional consequences, but whether the two components of restricted activity have comparable effects is unknown. We evaluated whether an illness/injury leading to bed rest represents a more potent exposure than one leading to cutting down on one's usual activities without bed rest.

We prospectively evaluated 754 community-living persons, 70+ years. Telephone interviews were completed monthly for >15 years to assess disability in four basic, five instrumental, and four mobility activities and to ascertain exposure to illnesses/injuries leading to cut down activities and bed rest, respectively. For each of the three functional domains, transitions between no disability, mild disability, and severe disability were evaluated each month.

For each domain, cut down activities and bed rest were significantly associated with at least one transition. The associations were consistently stronger, however, for bed rest than for cut down activities. Bed rest was a particularly potent exposure for transitions from no disability to severe disability, with hazard ratios as high as 8.94 (95% CI, 5.69-14.1) for the mobility activities, and for all transitions from severe disability (representing recovery), with hazard ratios as low as 0.25 (0.12-0.54) for the transition to no disability for the basic activities.

In the setting of an illness/injury, bed rest was more strongly associated with a set of clinically meaningful transitions in functional status than cut down activities. Prompt medical attention may be warranted when an older person takes to bed because of an illness/injury.