Perception of Energy and Objective Measures of Physical Activity in Older Adults

To the Editor: Perceived energy predicts survival, physical function, and physical activity (PA).1-5 However, the evidence is among patient populations or young adults. Whether perceived energy plays a role in PA and health outcomes in older adults living in the community is unknown. We hypothesized that in older men and women, higher self-reported energy would be associated with higher levels of PA assessed objectively via the SenseWear Armband (SWA). Assessing perceived energy levels may offer a potential behavioral screening test for PA behaviors among community-dwelling older adults, who are likely to benefit from continued PA behaviors. We identified 96 participants from the Health, Aging and Body Composition Study with concurrent data on self-reported energy and SWA between 2011 and 2012. All participants provided written informed consent. The University of Pittsburgh institutional review board approved the protocol. Participants answered the question “What was your usual energy level during the past month?” on a 0 to 10 scale, with 0 indicating no energy and 10 indicating the most energy. We used the SWA to detect daily mean total energy expenditure (kcal), active energy expenditure (kcal), intensity (metabolic equivalents [METs]), duration (minutes) of PA (≥3 METs), and step counts. SWA measures were obtained via pattern detection algorithms,6 with good accuracy and reliability in a free-living environment, validated in older adults.7 Participants were instructed to wear the SWA on the left upper arm for 7 consecutive days (SenseWear Pro 7.0). Data with 3 days or longer of the on-body time were included. Values above 4 standard deviations (SDs) were excluded for analysis. Other measures of interest included physical function measured as usual pace gait speed while walking a 4-m-long walkway using the GaitMat II system (EQ Inc, Chalfont, PA). Depressive symptoms were measured using the Center for Epidemiologic Study Depression Scale short form (CES-D 10), a 10-item scale scored from 0 to 30.8 Dementia diagnosis was adjudicated using an extensive neuropsychological battery and medical records since 1997.6 Associations of self-reported energy with SWA measures and other variables were tested using the Spearman correlation and independent t tests as appropriate (SAS v.9.4; SAS Institute, Inc, Cary, NC). The association of self-reported energy with each SWA measure was adjusted for usual gait speed because physical function may limit PA participation in older adults. We did not adjust for age, sex, body weight, and height because these were accounted for in the calculation of SWA measures.6 The study participants (mean age = 86.6 years [SD = 2.4]; 52% women; 45% black) had a mean self-report energy of 6.0 (SD = 2.0) and usual gait speed of .81 m/second (SD = .20). A total of 11% had dementia. Self-reported energy was not associated with age, sex, race, education level, gait speed, or cognitive status (P > .05). There was a trend of higher self-reported energy associated with lower CES-D 10 (P = .08). Self-reported energy was positively associated with daily active energy expenditure, METs, minutes of PA, and step counts but not with total energy expenditure (Figure 1). After controlling for gait speed, results remained substantially unchanged. In this sample of older adults in their 80s, self-reported energy was positively associated with PA behaviors and the amount of energy expended while being active, independent of physical function. Associations were consistent across PA measures, albeit stronger for step counts and intensity (effect size toward moderate9). Perhaps step counts and intensity capture a wider spectrum of PA compared with active energy expenditure and duration that measure activities at or above 3 METs. Self-reported energy was not associated with total energy expenditure, perhaps because total energy expenditure also includes energy spent for food thermogenesis and for homeostasis including resting metabolic rate.10 The trend of perceived energy with depressive symptoms suggests a role in psychological factors or motivation. However, we did not find an association with cognitive status. Limitations include modest sample size, somewhat healthier than the general population due to their voluntary participation and eligibility for brain magnetic resonance imaging.6 This study is cross sectional, and causation or direction of association cannot be established. It is possible that physically active individuals feel more energy. The relationship may also be bidirectional or explained by a common cause. The use of SWA is a strength because it provided a wealth of validated energy expenditure and PA measures.7 The study sample is well-characterized multiracial (45% black) community-dwelling older adults including both men and women. In sum, assessing energy levels on a simple 0 to 10 scale may offer a potential behavioral screening test to identify older individuals who lead a sedentary lifestyle. These individuals may be targeted for tailored counseling and/or coaching to reduce the risks of being sedentary. Longitudinal studies of self-reported energy predicting changes in PA are warranted. This research was supported in part by the Intramural Research Program of the National Institute on Aging (NIA). This research was supported by NIA Contracts N01-AG-6-2101, N01-AG-6-2103, and N01-AG-6-2106; NIA Grants R01-AG028050, P30-AG024827, T32AG055381, and U01AG061393; and a National Institute of Nursing Research (Grant R01-NR012459). It was also supported by the 8th Annual Department of Epidemiology Small Grant Program, University of Pittsburgh. The authors have declared no conflicts of interest for this article. Study concept and design, data collection, analysis and interpretation of data, and preparation of the manuscript: Tian. Interpretation of data and critical evaluation of the manuscript: Glynn. Critical evaluation of the manuscript: Ehrenkranz, Sprague, and Rosso. Study concept and design, data collection, interpretation of data, and critical evaluation of the manuscript: Rosano. None.