Actigraphic assessment of the circadian rest-activity rhythm in elderly patients hospitalized in an acute care unit.

Hospitalization for acute illness is a major risk factor of rest-activity rhythm disturbance among elderly subjects. The rest-activity rhythm is disturbed by the acute illness, aging and hospital environment. The purpose of this study is to assess the rest-activity rhythm and light exposure (using a wrist worn actigraph) of 10 patients (mean age 81 years, seven females) admitted on an acute care unit, suffering from cardiac, respiratory or renal acute disease. A non-parametric method was used to analyze activity data. With an improvement of the underlying diseases, the mean relative amplitude of rhythm increased from 0.31 +/- 0.19 for the first 5-day period after admission to 0.54 +/- 0.21 for the second period before discharge (P < 0.05). The amount of time at night spent above a lighting threshold of 50 lux decreased from 31.4 to 12.3 min between the two periods. The rhythm of elderly subjects hospitalized in the acute care unit is severely altered during the initial period and is progressively resynchronized following clinical improvement. Under the acute underlying disease and/or aging, environmental conditions (light, noise) should be considered to maintain regular rest-activity rhythm.