Fatigability disrupts cognitive processes' regulation of inflammatory reactivity in old age

Fatigue in community-dwelling older adults: A review of definitions, measures, and related factors

Fatigue is a common age-related symptom among community-dwelling adults aged 65 years and older. Yet, a systematic approach has rarely been applied to review definitions, measures, related factors, and consequences of fatigue in this population. A scoping review was conducted in December 2020 to fill the gap, and 36 articles met the inclusion criteria. Definitions, albeit diverse, included at least one of the following attributes: an early indicator of disablement, subjective, a lack of energy, multidimensional, impaired daily activities, and temporal. A summary of fatigue measures used in this population was provided, including a brief overview, number of items, reliability, and validity. In general, different measures were used with considerable variability in the content. Additionally, most measures had limited information on test-retest reliability and validity. Fatigue-related factors mapped into biological, psychological, social, and behavioral factors. Fatigue consequences were primarily declines in physical and cognitive functions. (100-150 words).

Validation of Perceived Mental Fatigability Using the Pittsburgh Fatigability Scale

OBJECTIVES

Establish reliability, concurrent and convergent validity of the Pittsburgh Fatigability Scale (PFS) Mental subscale.

DESIGN

Cross-sectional.

SETTING

Older adults from two University of Pittsburgh registries, Baltimore Longitudinal Study of Aging (BLSA), and Long Life Family Study (LLFS).

PARTICIPANTS

PFS Mental subscale validation was conducted using three cohorts: (1) Development Sample (N = 664, 59.1% women, age 74.8 ± 6.4 years, PFS Mental scores 10.3 ± 9.1), (2) Validation Sample I-BLSA (N = 430, 51.9% women, age 74.5 ± 8.2 years, PFS Mental scores 9.4 ± 7.9), and (3) Validation Sample II-LLFS (N = 1,917, 54.5% women, age 72.2 ± 9.3 years, PFS Mental scores 7.5 ± 8.2).

MEASUREMENTS

Development Sample, Validation Sample I-BLSA, and Validation Sample II-LLFS participants self-administered the 10-item Pittsburgh Fatigability Scale. Validation Sample II-LLFS completed cognition measures (Trail Making Tests A and B), depressive symptomatology (Center for Epidemiologic Studies-Depression Scale, CES-D), and global fatigue from two CES-D items.

RESULTS

In the Development Sample and Validation Sample I-BLSA, confirmatory factor analysis showed all 10 items loaded on two factors: social and physical activities (fit indices: SRMSR = 0.064, RMSEA = 0.095, CFI = 0.91). PFS Mental scores had strong internal consistency (Cronbach's α = 0.85) and good test-retest reliability (ICC = 0.78). Validation Sample II-LLFS PFS Mental scores demonstrated moderate concurrent and construct validity using Pearson (r) or Spearman (ρ) correlations against measures of cognition (Trail Making Tests A (r = 0.14) and B (r = 0.17) time), depressive symptoms (r = 0.31), and global fatigue (ρ = 0.21). Additionally, the PFS Mental subscale had strong convergent validity, discriminating according to established clinical or cognitive testing cut points, with differences in PFS Mental scores ranging from 3.9 to 7.6 points (all P < .001). All analyses were adjusted for family relatedness, field center, age, sex, and education.

CONCLUSIONS

The validated PFS Mental subscale may be used in clinical and research settings as a sensitive, one-page self-administered tool of perceived mental fatigability in older adults.

Slower information processing speed is associated with persistent burnout symptoms but not depression symptoms in nursing workers

Introduction: Burnout and depression both occur with chronic work-related stress, and cognitive deficits have been found when symptom severity results in work disability. Less is known about cognitive deficits associated with milder symptoms among active workers, and few studies have examined whether cognitive deficits predict persistent burnout and depression symptoms. The goal of this study was to examine the association of information processing speed and executive function performance to burnout and depression symptoms at baseline and 12-month follow-up in a sample of actively working individuals (N = 372).Method: The design was prospective with laboratory cognitive data at baseline, and burnout and depressive symptoms assessed at baseline and monthly follow-ups. Information processing speed and executive functions were assessed in a task-switching paradigm, including single-task reaction time (RT), switching costs, and mixing costs. Burnout was assessed with the Exhaustion subscale of the Oldenburg Burnout Inventory and depression with the Patient Health Questionnaire-9.Results: Slower RT was modestly associated with higher levels of burnout symptoms both cross-sectionally and prospectively, but switching costs and mixing costs were not associated with burnout symptoms. None of the cognitive measures were associated with depression symptoms cross-sectionally or prospectively.Conclusions: Despite statistically significant findings of slowed RT in acute exhaustion-related burnout, the proportion of variance accounted for in the models was small and did not predict clinically significant levels of distress. The absence of statistically significant findings for depression symptoms suggests the cognitive profile associated with the exhaustion dimension of burnout may be distinct from that of depression, which reflects a more heterogeneous symptomatology. Our data suggest the clinical impact of burnout symptoms on actively working individuals is marginal; nonetheless, it is important to screen and intervene on burnout and depression symptoms in the workplace because they can lead to other forms of work impairment.

Brain structural connectomes indicate shared neural circuitry involved in subjective experience of cognitive and physical fatigue in older adults

Cumulative evidence suggests the existence of common processes underlying subjective experience of cognitive and physical fatigue. However, mechanistic understanding of the brain structural connections underlying the experience of fatigue in general, without the influence of clinical conditions, is limited. The purpose of the study was to examine the relationship between structural connectivity and perceived state fatigue in older adults. We enrolled cognitively and physically healthy older individuals (n = 52) and categorized them into three groups (low cognitive/low physical fatigue; low cognitive/high physical fatigue; high cognitive/low physical fatigue; no subjects had high cognitive/high physical fatigue) based on perceived fatigue from cognitive and physical fatigue manipulation tasks. Using sophisticated diffusion tensor imaging processing techniques, we extracted connectome matrices for six different characteristics of whole-brain structural connections for each subject. Tensor network principal component analysis was used to examine group differences in these connectome matrices, and extract principal brain networks for each group. Connected surface area of principal brain networks differentiated the two high fatigue groups from the low cognitive/physical fatigue group (high vs. low physical fatigue, p = 0.046; high vs. low cognitive fatigue, p = 0.036). Greater connected surface area within striatal-frontal-parietal networks was correlated with lower cognitive and physical fatigue, and was predictive of perceived physical and cognitive fatigue measures not used for group categorization (Pittsburgh fatigability physical subscale, R2 = 0.70, p < 0.0001; difference in self-report fatigue before and after gambling tasks, R2 = 0.54, p < 0.0001). There are potentially structural connectomes resilient to both cognitive and physical fatigue in older adults.

Insula and putamen centered functional connectivity networks reflect healthy agers' subjective experience of cognitive fatigue in multiple tasks

Cognitive fatigue (CF) impairs ability to perform daily activities, is a common complaint of aging and a symptom of multiple neurological conditions. However, knowledge of the neural basis of CF is limited. This is partially because CF is difficult to systematically modulate in brain imaging experiments. The most common approach has been to scan brain activity during effortful cognitive tasks. Consequently, neural correlates of CF tend to be task-specific and may vary across tasks. This makes it difficult to know how results generalize across studies and is outside the subjective experience of CF which tends to be similar in different tasks. It has been hypothesized that the subjective experience of CF might arise from domain general systems monitoring and acting on energy depletion in task specific circuits. Direct supporting neural evidence is lacking. By repeatedly scanning aging individuals undertaking four different tasks using functional Magnetic Resonance Imaging and referencing scans to detailed CF self-ratings taken before and after scanning, we sought task-general correlates of CF. We ran a data-driven representational similarity analysis, treating each brain region as a candidate CF functional connectivity hub, and correlating inter-participant differences in hub-based connectivity patterns with inter-participant differences in self-rated CF-profiles (a pattern of ratings across 18 questions). Both right insula and right putamen-based network connectivity patterns reflected CF across all tasks and could underpin subjective experience of CF.

Evaluation of fatigability measurement: Integrative review

Fatigability is defined as the extent of fatigue in the context of activity and differs from the term used in exercise literature to describe muscle endurance characteristics. Many fatigability measures are available, but no studies have thoroughly evaluated them for adequate incorporation of fatigability concepts. This integrative review provides an overall assessment of existing fatigability measures and then evaluates each in depth. A database search and hand search produced 14 studies for review. Fatigability measurement took three forms: self-reported fatigability, perceived fatigability (self-reported fatigue following a defined performance test), and performance fatigability (performance deterioration). Of 17 measures identified, validity and/or reliability was reported for six (35.3%), and no measure was used in more than one study. Fatigability measures have been correlated with clinical measures, indicating that fatigability should be measured during routine clinical health screening. Refinement of measures and additional fatigability data collection will improve understanding and treatment of fatigue.

Mental Fatigability and Heart Rate Variability in Mild Cognitive Impairment

OBJECTIVES

Adaptive physiological stress regulation is rarely studied in mild cognitive impairment (MCI). Here we targeted mental fatigability (MF) as a determinant of altered high frequency heart rate variability (HF-HRV) reactivity in individuals with MCI, and examined frontobasal ganglia circuitry as a neural basis supporting the link between MF and HF-HRV reactivity.

METHODS

We measured mental fatigability and HF-HRV during a 60-minute cognitive stress protocol in 19 individuals with MCI. HF-HRV responses were modeled using a quadratic equation. Resting state functional connectivity of intra- and inter-network frontobasal ganglia circuitry was assessed using blood-oxygen-level-dependent magnetic resonance imaging among seven of the participants.

RESULTS

Lower MF was associated with faster and greater rebound in U-shape HF-HRV reactivity, which linked to a stronger connectivity between right middle frontal gyrus and left putamen.

CONCLUSIONS

Results suggest that MF may contribute to abnormal physiological stress regulation in MCI, and fronto basal ganglia circuitry may support the link.