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Introduction: Low physical activity is a criterion of phenotypic frailty defined as an increased state of vulnerability to adverse health outcomes. Whether disengagement from daily all-purpose physical activity is prospectively associated with frailty and possibly modified by chronic inflammation—a pathway often underlying frailty—remains unexplored. Methods: Using the Study to Understand Fall Reduction and Vitamin D in You data from 477 robust/prefrail adults (mean age = 76 ± 5 yr; 42% women), we examined whether accelerometer patterns (activity counts per day, active minutes per day, and activity fragmentation [broken accumulation]) were associated with incident frailty using Cox proportional hazard regression. Baseline interactions between each accelerometer metric and markers of inflammation that include interleukin-6, C-reactive protein, and tumor necrosis factor-alpha receptor 1 were also examined. Results: Over an average of 1.3 yr, 42 participants (9%) developed frailty. In Cox regression models adjusted for demographics, medical conditions, and device wear days, every 30 min·d−1 higher baseline active time, 100,000 more activity counts per day, and 1% lower activity fragmentation was associated with a 16% (P = 0.003), 13% (P = 0.001), and 8% (P < 0.001) lower risk of frailty, respectively. No interactions between accelerometer metrics and baseline interleukin-6, C-reactive protein, or tumor necrosis factor-alpha receptor 1 were detected (interaction P > 0.06 for all). Conclusions: Among older adults who are either robust or prefrail, constricted patterns of daily physical activity (i.e., lower total activity minutes and counts, and higher activity fragmentation) were prospectively associated with higher risk of frailty but not modified by frailty-related chronic inflammation. Additional studies, particularly trials, are needed to understand if this association is causal. [ABSTRACT FROM AUTHOR]

Background: Gradual disengagement from daily physical activity (PA) could signal present or emerging mild cognitive impairment (MCI) or Alzheimer's disease (AD).Objective: This study examined whether accelerometry-derived patterns of everyday movement differ by cognitive diagnosis in participants of the Baltimore Longitudinal Study of Aging (BLSA).Methods: Activity patterns, overall and by time-of-day, were cross-sectionally compared between participants with adjudicated normal cognition (n = 549) and MCI/AD diagnoses (n = 36; 5 participants [14%] living with AD) using covariate-adjusted regression models.Results: Compared to those with normal cognition, those with MCI/AD had 2.1% higher activity fragmentation (SE = 1.0%, p = 0.036) but similar mean total activity counts/day (p = 0.075) and minutes/day spent active (p = 0.174). Time-of-day analyses show MCI/AD participants had lower activity counts and minutes spent active during waking hours (6:00 am-5:59 pm; p < 0.01 for all). Also, they had lower activity fragmentation from 12:00-5:59 am (p < 0.001), but higher fragmentation from 12:00-5:59 pm (p = 0.026).Conclusion: Differences in the timing and patterns of physical activity throughout the day linked to MCI/AD diagnoses warrant further investigation into potential clinical utility. [ABSTRACT FROM AUTHOR]

Background: Fatigability, defined as fatigue in relation to a standardized task, predicts functional decline in older adults independent of reported tiredness or energy level. Although the sensation of fatigue, tiredness, and energy level adversely affect physical activity (PA), the association between fatigability and objectively measured PA is unknown.Methods: Participants in the Baltimore Longitudinal Study of Aging (n = 557, 50% women, aged 50-97 years) were instructed to wear an Actiheart accelerometer for 7 consecutive days in the free-living environment. Perceived fatigability was assessed using the Borg rating of perceived exertion (RPE) after 5 minutes of treadmill walking at 1.5 mph (0.67 m/s) and categorized as low (6-7 RPE), intermediate (8-9 RPE), and high (10+ RPE) fatigability. Time-of-day PA differences between fatigability groups were assessed using mixed-effects modeling.Results: Total daily PA was 1.3% lower for every unit increment in perceived fatigability after adjusting for demographic, behavioral, and medical factors (p = .01). In time-of-day analyses, the high fatigability group was less active compared to the low fatigability group throughout the day (8:00 am to 8:00 pm) and the intermediate fatigability group in the morning (8:00 am to 12:00 pm). Patterns of PA within the high fatigability group differed from both the intermediate and low groups in the morning but mirrored the intermediate group in the afternoon and evening.Discussion: These results suggest that RPE is a bio-marker of fatigability associated with progressively lower PA with aging. Whether the effects of fatigability occurring at the end of the day reflect waning energy levels or a voluntary choice that could be modified remains to be evaluated. [ABSTRACT FROM AUTHOR]

PURPOSE: To describe the epidemiology of objectively measured physical activity among older adults participating in the Baltimore Longitudinal Study of Aging (BLSA), America's longest running study of human aging, which switched to wrist-worn accelerometry collected since 2015. METHODS: Data were from 658 participants (mean age 70 years, 55% women) enrolled in the BLSA who were instructed to wear a wrist-worn accelerometer for 7 consecutive days and were seen in clinic between 2015-2019. Accelerometer data were processed into activity counts (unitless quantities of movement) and summarized into three continuous metrics: 1) total activity counts/d; 2) active minutes/d using a threshold of ≥1,853 counts/min; and 3) activity fragmentation defined as the reciprocal of the mean active bout length (consecutively occurring active minutes) x 100 (%). Since the BLSA visit schedule is age-dependent (i.e., older persons have more repeated visits), longitudinal analyses were conducted in a restricted sample aged ≥65 years old (n=225). Mixed effects models were constructed to estimate longitudinal changes (baseline age x years since baseline) in each accelerometer metric. Years since baseline was treated as a random effect. Covariates included sex, race, education, employment, body mass index, chronic conditions, usual gait speed, and wear days. RESULTS: Participants, aged 22-97 years, had a mean total 2,209,488 activity counts/d, 430 active minutes/d and 24% activity fragmentation at baseline. Mean wear time was high (1440 min/d) and mean wear days was 6 days. The longitudinal sample, aged 65-97 years, descriptively engaged in less physical activity at baseline, with a mean of 2,060,886 activity counts/d, 414 active minutes/d and activity fragmentation of 25%. Mixed effects modeling estimates showed that, per year, total activity counts decreased by 4894 (SE=1379, p<0.001) counts/d, activity minutes decreased by 1 (SE=0.28, p=0.001) min/d, and activity fragmentation increased by 0.06 (SE=0.02, p=0.0001) %. CONCLUSIONS: Findings update objectively measured physical activity patterns previously measured in the BLSA. With more studies switching to wrist accelerometry collection, these results help define and characterize physical activity patterns and longitudinal change, particularly later in life. [ABSTRACT FROM AUTHOR]

Introduction/Purpose: Fatigue is an established prognostic indicator of mortality risk. It remains unknown whether fatigability anchored to a physical task is a more sensitive prognostic indicator and whether sensitivity differs by prevalent chronic conditions. Methods: A total of 1076 physically well-functioning participants 50 yr or older in the Baltimore Longitudinal Study of Aging self-reported fatigue (unusual tiredness or low energy) and had perceived fatigability assessed after a standardized treadmill walk. All-cause mortality was ascertained by proxy contact and National Death Index linkage. Cox proportional hazards models estimated associations of perceived fatigability and fatigue with all-cause mortality, adjusting for demographic and clinical covariates. Interactions by chronic conditions were also examined. Results: Each 1 SD higher in perceived fatigability, unusual tiredness, or low energy was associated with a higher relative hazard of all-cause mortality after covariate adjustment (fatigability: hazard ratio (HR), 1.18 (95% confidence interval (CI), 1.03–1.36); unusual tiredness: HR, 1.25 (95% CI, 1.08–1.44); low energy: HR, 1.27 (95% CI, 1.10–1.46)). Models had similar discrimination (P > 0.14 for all). Perceived fatigability was associated with mortality risk among participants free of arthritis or osteoarthritis who otherwise appeared healthy (no arthritis: HR, 1.45 (95% CI, 1.15–1.84); arthritis: HR, 1.09 (95% CI, 0.92–1.30); P -interaction = 0.031). Unusual tiredness was associated with mortality among those with a history of diabetes (no diabetes: HR, 1.16 (95% CI, 0.97–1.38); diabetes: HR, 1.65 (95% CI, 1.22–2.23); P -interaction = 0.045) or pulmonary disease (no pulmonary disease: HR, 1.22 (95% CI, 1.05–1.43); pulmonary disease: HR, 2.15 (95% CI, 1.15–4.03); P -interaction = 0.034). Conclusions: Higher perceived fatigability and fatigue symptoms were similarly associated with higher all-cause mortality, but utility differed by chronic condition. Perceived fatigability might be useful for health screening and long-term mortality risk assessment for well-functioning adults. Alternatively, self-reported fatigue seems more disease-specific with regard to mortality risk. [ABSTRACT FROM AUTHOR]