Maximum daily 6 minutes of activity: an index of functional capacity derived from actigraphy and its application to older adults with heart failure.

OBJECTIVES: To compare the correlation between the maximum 6 minutes of daily activity (M6min) and standard measures of functional capacity in older adults with heart failure (HF) with that in younger subjects and its prognostic utility. DESIGN: Prospective, cohort study. SETTING: Tertiary care, academic HF center. PARTICIPANTS: Sixty, ambulatory, adults, New York Heart Association (NYHA) Class I to III, stratified into young (50.9 +/- 9.4) and older cohorts (76.8 +/- 8.0). MEASUREMENTS: Correlation between M6min and measures of functional capacity (6-minute walk test; 6MWT) and peak oxygen consumption (VO(2)) according to cardiopulmonary exercise testing in a subset of subjects. Survival analysis was employed to evaluate the association between M6min and adverse events. RESULTS: Adherence to actigraphy was high (90%) and did not differ according to age. The correlation between M6min and 6MWT was higher in subjects aged 65 and older than in those younger than 65 (correlation coefficient (r=0.702, P<.001 vs r=0.490, P=.002). M6min was also significantly associated with peak VO(2) (r=0.612, P=.006). During the study, 26 events occurred (2 deaths, 10 hospitalizations, 8 emergency department visits, and 6 intercurrent illnesses). The M6min was significantly associated with subsequent events (hazard ratio=2.728, 95% confidence interval=1.10-6.77, P=.03), independent of age, sex, ejection fraction, NYHA class, brain natriuretic peptide, and 6MWT. CONCLUSION: The high adherence to actigraphy and association with standard measures of functional capacity and independent association with subsequent morbid events suggest that it may be useful for monitoring older adults with HF.

The prevalence and impact of anergia (lack of energy) in subjects with heart failure and its associations with actigraphy.

BACKGROUND: Anergia (lack of energy) is a newly delineated, criterion-based geriatric syndrome. Because heart failure (HF) is a common chronic condition among older adults and a because a cardinal symptom of HF is reduced energy, we characterized the degree of anergia in subjects with HF and evaluated its relevance to disease severity, functional performance, and quality of life. METHODS AND RESULTS: Prospective 3-month cohort study among a convenience sample of 61 subjects (61 +/- 15 years, 48% women, ejection fraction 41 +/- 16%) with New York Heart Association (NYHA) Class I-III HF were studied. The criterion for anergia was based on the major criterion "sits around for lack of energy" and any 2 of 6 minor criteria. Principal measures in addition to demographic and clinical characteristics included functional performance (NYHA class, 6-minute walk, cardiopulmonary exercise testing), plasma B-type natriuretic peptide, and quality of life (SF-12 and Minnesota Living with Heart Failure Questionnaire). To evaluate the relevance of anergia to daily function, each subject wore an Actigraph, a watch-like wrist device that continuously and automatically monitors patient activity levels and energy expenditure, for 3 months. Anergia was prevalent in 39% of this population. Anergia was associated with decrements in functional capacity (higher NYHA Class and lower 6-minute walk distance) as well as reduction in quality of life, but was not associated with ejection fraction. Actigraphy data demonstrated that HF subjects with anergia spent significantly less time performing moderate physical activity and the peak activity counts per day were significantly lower than HF subjects without anergia. Additionally, the amplitude of circadian rhythm was lower, suggesting altered sleep and activity patterns in HF subjects with anergia compared with those without anergia. Over the 3 months of follow-up, there was a significant association between anergia and intercurrent hospitalization. CONCLUSIONS: Anergia is significantly associated with several of the cardinal domains of HF. Its presence is associated with demonstrable differences in both physical activity and circadian rhythm as measured by actigraphy and an increased risk of hospitalizations. Accordingly, anergia may be a target for intervention among HF subjects.