Effects of age on activity patterns after coronary artery bypass surgery

Objective: To examine the effect of age on activity patterns, including circadian rhythms and levels, after coronary artery bypass surgery (CABS). Design: Repeated measures, correlational. Setting: Northeastern university-affiliated tertiary coronary care center. Subjects: Eight middle-aged (mean age = 57 years) and 14 older (mean age = 72 years) adults who had undergone first, isolated CABS. Outcome Measures: Wrist actigraph measures of levels (daytime activity) and circadian patterns of activity (acrophase, amplitude, percent rhythm, mesor), self-reported postoperative clinical activity milestones, and Sickness Impact Profile subscales of ambulation dysfunction and sleep-rest. Intervention: Measurement of activity over postoperative days 2 through 5, including wrist actigraphy, Sickness Impact Profile ambulation and sleep-rest subscales, and daily clinical activity milestones. Results: Repeated measures ANOVA was used in the data analysis. Statistically significant increases were found in percent rhythm (P < .001), amplitude (P < .001), activity level (P < .001), and clinical activity milestones (P < .001) over postoperative days 2 through 5. Significant effects of age were found on amplitude (P = .02) and percent rhythm (P = .008). Significant age-by-time effects were found for circadian amplitude (P = .03) and percent rhythm (P = .02). There was a nonstatistically significant (P = .07) age by time interaction effect on daytime activity. Trends in amplitude, percent rhythm, and daytime activity indicated that these activity parameters increased more slowly in older adults, compared with middle-aged adults, after initially similar levels on postoperative days 2 and 3. Conclusion: Both middle-aged and older adults increase daily activity and the strength of circadian activity pattern over days 2 through 5. However, these variables increase more rapidly in middle-aged adults after essentially identical levels on postoperative days 2 and 3. (Heart Lung® 1999;28:5-14)