Effects of age on activity patterns after coronary artery bypass surgery

OBJECTIVE: To examine the effect of age on activity patterns, including cir cadian 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, meso r), 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-re st subscales, and daily clinical activity milestones. RESULTS: Repeated measures ANOVA was used in the data analysis. Statistical ly 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 = .088). Significant age -by-time effects were found for circadian amplitude (P = .03) and percent r hythm (P =.02). There was a nonstatistically significant (P = .07) age by l ime interaction effect on daytime activity. Trends in amplitude, percent rh ythm, and daytime activity indicated that these activity parameters increas ed more slowly in older adults, compared with middle-aged adults, after ini tially similar levels on postoperative days 2 and 3. CONCLUSION: Both middle-aged and older adults increase daily activity and t he strength of circadian activity pattern over days 2 through 5. However, t here variables increase more rapidly in middle-aged adults after essentiall y identical levels on postoperative days 2 and 3.