Dawn C. Mackey

Validation of an Armband to Measure Daily Energy Expenditure in Older Adults

BACKGROUND Objective methods to measure daily energy expenditure in studies of aging are needed. We sought to determine the accuracy of total energy expenditure (TEE) and activity energy expenditure (AEE) estimates from the SenseWear Pro armband (SWA) using software versions 6.1 (SWA 6.1) and 5.1 (SWA 5.1) relative to criterion methods in free-living older adults. METHODS Participants (n = 19, mean age 82.0 years) wore a SWA for a mean ± SD 12.5 ± 1.1 days, including while sleeping. During this same period, criterion values for TEE were assessed with doubly labeled water and for resting metabolic rate (RMR) with indirect calorimetry. AEE was calculated as 0.9 TEE - RMR. RESULTS For TEE, there was no difference in mean ± SD values from doubly labeled water (2,040 ± 472 kcal/day) versus SWA 6.1 (2,012 ± 497 kcal/day, p = .593) or SWA 5.1 (2,066 ± 474 kcal/day, p = .606); individual values were highly correlated between methods (SWA 6.1 r = .893, p < .001; SWA 5.1 r = .901, p < .001) and demonstrated strong agreement (SWA 6.1 intraclass correlation coefficient = .896; SWA 5.1 intraclass correlation coefficient = .904). For AEE, mean values from SWA 6.1 (427 ± 304 kcal/day) were lower by 26.8% than criterion values (583 ± 242 kcal/day, p = .003), and mean values from SWA 5.1 (475 ± 299 kcal/day) were lower by 18.5% than criterion values (p = .021); however, individual values were highly correlated between methods (SWA 6.1 r = .760, p < .001; SWA 5.1 r = .786, p < .001) and demonstrated moderate agreement (SWA 6.1 intraclass correlation coefficient = .645; SWA 5.1 intraclass correlation coefficient = .720). Bland-Altman plots identified no systematic bias for TEE or AEE. CONCLUSIONS Acceptable levels of agreement were observed between SWA and criterion measurements of TEE and AEE in older adults.

Skeletal Muscle Mitochondrial Energetics Are Associated With Maximal Aerobic Capacity and Walking Speed in Older Adults

BACKGROUND Lower ambulatory performance with aging may be related to a reduced oxidative capacity within skeletal muscle. This study examined the associations between skeletal muscle mitochondrial capacity and efficiency with walking performance in a group of older adults. METHODS Thirty-seven older adults (mean age 78 years; 21 men and 16 women) completed an aerobic capacity (VO2 peak) test and measurement of preferred walking speed over 400 m. Maximal coupled (State 3; St3) mitochondrial respiration was determined by high-resolution respirometry in saponin-permeabilized myofibers obtained from percutanous biopsies of vastus lateralis (n = 22). Maximal phosphorylation capacity (ATPmax) of vastus lateralis was determined in vivo by (31)P magnetic resonance spectroscopy (n = 30). Quadriceps contractile volume was determined by magnetic resonance imaging. Mitochondrial efficiency (max ATP production/max O2 consumption) was characterized using ATPmax per St3 respiration (ATPmax/St3). RESULTS In vitro St3 respiration was significantly correlated with in vivo ATPmax (r (2) = .47, p = .004). Total oxidative capacity of the quadriceps (St3*quadriceps contractile volume) was a determinant of VO2 peak (r (2) = .33, p = .006). ATPmax (r (2) = .158, p = .03) and VO2 peak (r (2) = .475, p < .0001) were correlated with preferred walking speed. Inclusion of both ATPmax/St3 and VO2 peak in a multiple linear regression model improved the prediction of preferred walking speed (r (2) = .647, p < .0001), suggesting that mitochondrial efficiency is an important determinant for preferred walking speed. CONCLUSIONS Lower mitochondrial capacity and efficiency were both associated with slower walking speed within a group of older participants with a wide range of function. In addition to aerobic capacity, lower mitochondrial capacity and efficiency likely play roles in slowing gait speed with age.

Physical performance and risk of hip fractures in older men

The aim of these analyses was to describe the association between physical performance and risk of hip fractures in older men. Performance on five physical function exams (leg power, grip strength, usual walking pace, narrow walk balance test, and five repeated chair stands) was assessed in 5902 men ≥65 yr of age. Performance (time to complete or strength) was analyzed as quartiles, with an additional category for unable to complete the measure, in proportional hazards models. Follow‐up averaged 5.3 yr; 77 incident hip fractures were confirmed by physician review of radiology reports. Poor physical performance was associated with an increased risk of hip fracture. In particular, repeated chair stand performance was strongly related to hip fracture risk. Men unable to complete this exam were much more likely to experience a hip fracture than men in the fastest quartile of this test (multivariate hazard ratio [MHR]: 8.15; 95% CI: 2.65, 25.03). Men with the worst performance (weakest/slowest quartile or unable) on at least three exams had an increased risk of hip fracture compared with men with higher functioning (MHR: 3.14, 95% CI: 1.46, 6.73). Nearly two thirds of the hip fractures (N = 49, 64%) occurred in men with poor performance on at least three exams. Poor physical function is independently associated with an increased risk of hip fracture in older men. The repeated chair stands exam should be considered in clinical settings for evaluation of hip fracture risk. Concurrent poor performance on multiple physical function exams is associated with an increased risk of hip fractures.

Statins and Physical Activity in Older Men: The Osteoporotic Fractures in Men Study

IMPORTANCE Muscle pain, fatigue, and weakness are common adverse effects of statin medications and may decrease physical activity in older men. OBJECTIVE To determine whether statin use is associated with physical activity, longitudinally and cross-sectionally. DESIGN, SETTING, AND PARTICIPANTS Men participating in the Osteoporotic Fractures in Men Study (N = 5994), a multicenter prospective cohort study of community-living men 65 years and older, enrolled between March 2000 and April 2002. Follow-up was conducted through 2009. EXPOSURES Statin use as determined by an inventory of medications (taken within the last 30 days). In cross-sectional analyses (n = 4137), statin use categories were users and nonusers. In longitudinal analyses (n = 3039), categories were prevalent users (baseline use and throughout the study), new users (initiated use during the study), and nonusers (never used). MAIN OUTCOMES AND MEASURES Self-reported physical activity at baseline and 2 follow-up visits using the Physical Activity Scale for the Elderly (PASE). At the third visit, an accelerometer measured metabolic equivalents (METs [kilocalories per kilogram per hour]) and minutes of moderate activity (METs ≥3.0), vigorous activity (METs ≥6.0), and sedentary behavior (METs ≤1.5). RESULTS At baseline, 989 men (24%) were users and 3148 (76%) were nonusers. The adjusted difference in baseline PASE between users and nonusers was -5.8 points (95% CI, -10.9 to -0.7 points). A total of 3039 men met the inclusion criteria for longitudinal analysis: 727 (24%) prevalent users, 845 (28%) new users, and 1467 (48%) nonusers. PASE score declined by a mean (95% CI) of 2.5 (2.0 to 3.0) points per year for nonusers and 2.8 (2.1 to 3.5) points per year for prevalent users, a nonstatistical difference (0.3 [-0.5 to 1.0] points). For new users, annual PASE score declined at a faster rate than nonusers (difference of 0.9 [95% CI, 0.1 to 1.7] points). A total of 3071 men had adequate accelerometry data, 1542 (50%) were statin users. Statin users expended less METs (0.03 [95% CI, 0.02-0.04] METs less) and engaged in less moderate physical activity (5.4 [95% CI, 1.9-8.8] fewer minutes per day), less vigorous activity (0.6 [95% CI, 0.1-1.1] fewer minutes per day), and more sedentary behavior (7.6 [95% CI, 2.6-12.4] greater minutes per day). CONCLUSIONS AND RELEVANCE Statin use was associated with modestly lower physical activity among community-living men, even after accounting for medical history and other potentially confounding factors. The clinical significance of these findings deserves further investigation.

Hospitalization and Change in Body Composition and Strength in a Population-Based Cohort of Older Persons

OBJECTIVES: To examine the association between hospitalization and annual changes in body composition and strength in older adults.

Prediction of Clinical Non‐Spine Fractures in Older Black and White Men and Women With Volumetric BMD of the Spine and Areal BMD of the Hip: The Health, Aging, and Body Composition Study

In a prospective study of 1446 black and white adults 70–79 yr of age (average follow‐up, 6.4 yr), vertebral TrvBMD from QCT predicted non‐spine fracture in black and white women and black men, but it was not a stronger predictor than total hip aBMD from DXA. Hip aBMD predicted non‐spine fracture in black men.

Activity energy expenditure and change in body composition in late life

BACKGROUND Change in body composition, specifically loss of fat-free mass and gain in fat mass, in older adults is a major pathway leading to the onset of functional decline and physical disability. OBJECTIVE The objective was to determine the association of activity-related energy expenditure with change in body mass and composition among older men and women. DESIGN Total energy expenditure (TEE) was assessed over 2 wk by using the doubly labeled water method in 302 community-dwelling older adults aged 70-82 y. Resting metabolic rate (RMR) was measured by using indirect calorimetry, and the thermic effect of meals was estimated at 10% of TEE. Activity energy expenditure (AEE) was calculated as [TEE(0.9) - RMR]. Total body mass, fat-free mass (FFM), and fat mass (FM) were assessed by dual-energy X-ray absorptiometry annually over a mean (+/-SD) of 4.9 +/- 1.3 y. RESULTS In multivariate models adjusted for baseline age, smoking status, and race, men and women had a decline (in kg/y) in body mass (men: -0.34, 95% CI: -0.71, 0.02; women: -0.45, 95% CI: -0.71, -0.19) and FFM (men: -0.48, 95% CI: -0.67, -0.29; women: -0.14, 95% CI: -0.026, -0.03). No changes (in kg/y) were observed in FM (men: 0.14, 95% CI: -0.10, 0.38; women: -0.28, 95% CI: -0.49, -0.07). In men and women, higher AEE at baseline was associated with greater FFM. The average change in these outcomes (ie, slope), however, was similar across tertiles of AEE. CONCLUSIONS These data suggest that accumulated energy expenditure from all physical activities is associated with greater FFM, but the effect does not alter the trajectory of FFM change in late life.

Changes in proximal femoral mineral geometry precede the onset of radiographic hip osteoarthritis: The study of osteoporotic fractures

OBJECTIVE Radiographic hip osteoarthritis (RHOA) is associated with increased hip areal bone mineral density (aBMD). This study was undertaken to examine whether femoral geometry is associated with RHOA independent of aBMD. METHODS Participants in the Study of Osteoporotic Fractures in whom pelvic radiographs had been obtained at visits 1 and 5 (mean 8.3 years apart) and hip dual x-ray absorptiometry (DXA) had been performed (2 years after baseline) were included. Prevalent and incident RHOA phenotypes were defined as composite (osteophytes and joint space narrowing [JSN]), atrophic (JSN without osteophytes), or osteophytic (femoral osteophytes without JSN). Analogous definitions of progression were based on minimum joint space and total osteophyte score. Hip DXA scans were assessed using the Hip Structural Analysis program to derive geometric measures, including femoral neck length, width, and centroid position. Relative risks and 95% confidence intervals for prevalent, incident, and progressive RHOA per SD increase in geometric measure were estimated in a hip-based analysis using multinomial logistic regression with adjustment for age, body mass index, knee height, and total hip aBMD. RESULTS In 5,245 women (mean age 72.6 years), a wider femoral neck with a more medial centroid position was associated with prevalent and incident osteophytic and composite RHOA phenotypes (P < 0.05). Increased neck width and centroid position were associated with osteophyte progression (both P < 0.05). No significant geometric associations with atrophic RHOA were found. CONCLUSION Differences in proximal femoral bone geometry and spatial distribution of bone mass occur early in hip OA and predict prevalent, incident, and progressive osteophytic and composite phenotypes, but not the atrophic phenotype. These bone differences may reflect responses to loading occurring early in the natural history of RHOA.

Skeletal Muscle Mitochondrial Function and Fatigability in Older Adults.

BACKGROUND Fatigability increases while the capacity for mitochondrial energy production tends to decrease significantly with age. Thus, diminished mitochondrial function may contribute to higher levels of fatigability in older adults. METHODS The relationship between fatigability and skeletal muscle mitochondrial function was examined in 30 participants aged 78.5 ± 5.0 years (47% female, 93% white), with a body mass index of 25.9 ± 2.7 kg/m(2) and usual gait-speed of 1.2 ± 0.2 m/s. Fatigability was defined using rating of perceived exertion (6-20 point Borg scale) after a 5-minute treadmill walk at 0.72 m/s. Phosphocreatine recovery in the quadriceps was measured using (31)P magnetic resonance spectroscopy and images of the quadriceps were captured to calculate quadriceps volume. ATPmax (mM ATP/s) and oxidative capacity of the quadriceps (ATPmax·Quadriceps volume) were calculated. Peak aerobic capacity (VO2peak) was measured using a modified Balke protocol. RESULTS ATPmax·Quadriceps volume was associated with VO2peak and was 162.61mM ATP·mL/s lower (p = .03) in those with high (rating of perceived exertion ≥10) versus low (rating of perceived exertion ≤9) fatigability. Participants with high fatigability required a significantly higher proportion of VO2peak to walk at 0.72 m/s compared with those with low fatigability (58.7 ± 19.4% vs 44.9 ± 13.2%, p < .05). After adjustment for age and sex, higher ATPmax was associated with lower odds of having high fatigability (odds ratio: 0.34, 95% CI: 0.11-1.01, p = .05). CONCLUSIONS Lower capacity for oxidative phosphorylation in the quadriceps, perhaps by contributing to lower VO2peak, is associated with higher fatigability in older adults.

Change in hip bone mineral density and risk of subsequent fractures in older men

Low bone mineral density (BMD) increases fracture risk; how changes in BMD influence fracture risk in older men is uncertain. BMD was assessed at two to three time points over 4.6 years using dual‐energy X‐ray absorptiometry (DXA) for 4470 men aged ≥65 years in the Osteoporotic Fractures in Men (MrOS) Study. Change in femoral neck BMD was estimated using mixed effects linear regression models. BMD change was categorized as “accelerated” (≤−0.034 g/cm2), “expected” (between 0 and −0.034 g/cm2), or “maintained” (≥0 g/cm2). Fractures were adjudicated by central medical record review. Multivariate proportional hazards models estimated the risk of hip, nonspine/nonhip, and nonspine fracture over 4.5 years after the final BMD measure, during which time 371 (8.3%) men experienced at least one nonspine fracture, including 78 (1.7%) hip fractures. Men with accelerated femoral neck BMD loss had an increased risk of nonspine (hazard ratio [HR] = 2.0; 95% confidence interval [CI] 1.4–2.8); nonspine/nonhip (HR = 1.6; 95% CI 1.1–2.3); and hip fracture (HR = 6.3; 95% CI 2.7–14.8) compared with men who maintained BMD over time. No difference in risk was seen for men with expected loss. Adjustment for the initial BMD measure did not alter the results. Adjustment for the final BMD measure attenuated the change in BMD‐nonspine fracture and the change in BMD‐nonspine/nonhip relationships such that they were no longer significant, whereas the change in the BMD‐hip fracture relationship was attenuated (HR = 2.6; 95% CI 1.1–6.4). Total hip BMD change produced similar results. Accelerated decrease in BMD is a strong, independent risk factor for hip and other nonspine fractures in men.