Physical Resilience: Not Simply the Opposite of Frailty

Closing the care gap: combining enhanced recovery with minimally invasive valve surgery

PURPOSE OF REVIEW

Patients with advanced age and frailty require interventions for structural heart disease at an increasing rate. These patients typically experience higher rates of postoperative morbidity, mortality and prolonged hospital length of stay, loss of independence as well as associated increased costs to the healthcare system. Therefore, it is becoming critically important to raise awareness and develop strategies to improve clinical outcomes in the contemporary, high-risk patient population undergoing cardiacprocedures.

RECENT FINDINGS

Percutaneous options for structural heart disease have dramatically improved the therapeutic options for some older, frail, high-risk patients; however, others may still require cardiac surgery. Minimally invasive techniques can reduce some of the physiologic burden experienced by patients undergoing surgery and improve recovery. Enhanced Recovery After Cardiac Surgery (ERAS Cardiac) is a comprehensive, interdisciplinary, evidence-based approach to perioperative care. It has been shown to improve recovery and patient satisfaction while reducing complications and length of stay.

SUMMARY

Combining minimally invasive cardiac surgery with enhanced recovery protocols may result in improved patient outcomes for a patient population at high risk of morbidity and mortality following cardiac surgery.

Frailty as an upstream target for intervention: A unifying approach to intervening in the trajectories of health, function, and disease in late life

This editorial comments on the article by Deiner et al. in this issue.

Effect of Frailty on Depression among Patients with Late-life Depression: A Test of Anger, Anxiety, and Resilience as Mediators

Objective

While the association between depression and frailty in the elderly population has been investigated, the psychological factors that mediate such a relationship remain unknown. The identification of psychological factors in interventions for depression treatment in the elderly may assist in the treatment and care. We aimed to explore the mediating effects of anger, anxiety, and resilience on the link between frailty and depression symptoms in patients with late-life depression.

Methods

A sample of 203 older adults completed questionnaires that assessed depression, anger, resilience, and anxiety. To measure frailty, participants were evaluated using a self-rated health questionnaire, weight-adjusted waist index related to sarcopenia, and weight-adjusted handgrip strength to evaluate weakness. A mediation model was tested, hypothesizing that anger, anxiety, and resilience would partially mediate the strength of the frailty-depression link in the elderly.

Results

Only self-rated health showed a significant association with depressive symptoms in late-life depression. Our study demonstrated that frailty has both direct and indirect associations with depression, mediated by anger, resilience, and anxiety.

Conclusion

Given that anger, resilience, and anxiety influence the link between self-rated health and depression, interventions that lead to increased resilience and decreased anger and anxiety may be promising to reduce depressive symptoms in older adults with depression.

The Evolution of Risk Assessment in Spine Surgery: A Narrative Review

BACKGROUND

Risk assessment is critically important in elective and high-risk interventions, particularly spine surgery. This narrative review describes the evolution of risk assessment from the earliest instruments focused on general surgical risk stratification, to more accurate and spine-specific risk calculators that quantified risk, to the current era of big data.

METHODS

The PubMed and SCOPUS databases were queried on October 11, 2023 using search terms to identify risk assessment tools (RATs) in spine surgery. A total of 108 manuscripts were included after screening with full-text review using the following inclusion criteria: 1) study population of adult spine surgical patients, 2) studies describing validation and subsequent performance of preoperative RATs, and 3) studies published in English.

RESULTS

Early RATs provided stratified patients into broad categories and allowed for improved communication between physicians. Subsequent risk calculators attempted to quantify risk by estimating general outcomes such as mortality, but then evolved to estimate spine-specific surgical complications. The integration of novel concepts such as invasiveness, frailty, genetic biomarkers, and sarcopenia led to the development of more sophisticated predictive models that estimate the risk of spine-specific complications and long-term outcomes.

CONCLUSIONS

RATs have undergone a transformative shift from generalized risk stratification to quantitative predictive models. The next generation of tools will likely involve integration of radiographic and genetic biomarkers, machine learning, and artificial intelligence to improve the accuracy of these models and better inform patients, surgeons, and payers.

Assessing dynamical resilience indicators in older adults: a prospective feasibility cohort study

PURPOSE

Measuring dynamical resilience indicators based on time series data may improve the prediction of health deterioration in older adults after hospital discharge. We examined the feasibility of an intensive prospective cohort study examining dynamical resilience indicators based on time series data of symptoms and physical activity in acutely ill older adults who visited the Emergency Department (ED).

METHODS

This is a prospective cohort study with time series data from symptom questionnaires and activity trackers. Thirty older adults (aged 75.9 ± 5.5 years, 37% female) who were discharged from the ED of a tertiary hospital in the Netherlands were included in the study. We monitored self-reported symptoms using a daily online questionnaire, and physical activity using an activity tracker for 30 days. Descriptive data on participant eligibility and adherence to and acceptability of the assessments were collected.

RESULTS

Of 134 older patients visiting the ED, 109/134 (81%) were eligible for inclusion and 30/109 (28%) were included. Twenty-eight (93%) of the included participants completed follow-up. Regarding the adherence rate, 78% of participants filled in the questionnaire and 80% wore the activity tracker. Three (10%) participants completed fewer than three questionnaires. Most participants rated the measurements as acceptable and seven (23%) participants experienced an adverse outcome in the 30 days after discharge.

CONCLUSION

Such an intensive prospective cohort study examining dynamical resilience indicators in older adults was feasible. The quality of the collected data was sufficient, some adjustments to the measurement protocol are recommended. This study is an important first step to study resilience in older adults.

Occupational Health Challenges for Aviation Workers Amid the Changing Climate: A Narrative Review

Although there are many forecasts regarding the impact of climate change on the aviation sector, a critical but frequently neglected dimension is the occupational safety risks faced by aviation professionals. This narrative review explores the potential impacts of the changing climate on the health and safety of aviation personnel. Furthermore, we examine the significance of resilience in helping these workers adapt and effectively manage climate-related challenges in their professional lives. Climate change poses increasing threats to the well-being of flight personnel through elevated temperatures, heightened ultraviolet radiation exposure, increased mental workload from extreme weather events, and other psychological stressors. Building resilience through workforce training, planning, and adaptation can reduce vulnerability. In future research, the iterative process of selecting measurement components to gauge the impact of climate change should balance feasibility, relevance for stakeholders, and accurately capturing exposure effects. For instance, while salivary cortisol measures stress biologically, assessments of depression or burnout may provide more nuanced insights on pilot health for industry decision-makers managing climate impacts. In conclusion, a strategic emphasis on enhancing the physical and psychological well-being of the aviation workforce is imperative for facilitating a more efficient adaptation within the sector. This is of paramount importance, considering the critical function that aviation serves in fostering human connectivity. Consequently, it is essential for regulatory bodies and policymakers to prioritize the safeguarding of employee health in the face of climate change challenges.

The impact of yoga on aging physiology: A review

Frailty represents diminished reserve across multiple physiologic systems, accompanied by increased vulnerability to stressors and increased morbidity and mortality. With population aging, strategies to prevent and manage frailty are priorities in clinical medicine and public health. Current evidence-based approaches to frailty management are multimodal in nature. Yoga, an increasingly popular and highly adaptable mind-body practice, is multi-component, incorporating physical postures, breathing practices, meditation, and other elements, and may be a strategy for frailty management. Here, we summarize the evidence linking yoga practice to mitigation of age-related degradation across multiple physiologic systems, including cardiovascular, pulmonary, musculoskeletal, and nervous systems. We discuss putative mechanisms of action including modulation of the hypothalamic-pituitary-adrenal axis. Finally, we consider implications for clinical practice and future research.

Physical Resilience as a Predictor of Lifespan and Late-Life Health in Genetically Heterogeneous Mice

Dynamic measures of resilience-the ability to resist and recover from a challenge-may be informative of the rate of aging before overt manifestations such as chronic disease, disability, and frailty. From this perspective mid-life resilience may predict longevity and late-life health. To test this hypothesis, we developed simple, reproducible, clinically relevant challenges, and outcome measures of physical resilience that revealed differences between and within age groups of genetically heterogeneous mice, and then examined associations between mid-life resilience and both lifespan and late-life measures of physiological function. We demonstrate that time to recovery from isoflurane anesthesia and weight change following a regimen of chemotherapy significantly differed among young, middle-aged, and older mice, and were more variable in older mice. Females that recovered faster than the median time from anesthesia (more resilient) at 12 months of age lived 8% longer than their counterparts, while more resilient males in mid-life exhibited better cardiac (fractional shortening and left ventricular volumes) and metabolic (glucose tolerance) function at 24 months of age. Moreover, female mice with less than the median weight loss at Day 3 of the cisplatin challenge lived 8% longer than those that lost more weight. In contrast, females who had more weight loss between Days 15 and 20 were relatively protected against early death. These data suggest that measures of physical resilience in mid-life may provide information about individual differences in aging, lifespan, and key parameters of late-life health.

Resilience, aging, and response to radiation exposure (RARRE) in nonhuman primates: a resource review

The Wake Forest nonhuman primate (NHP) Radiation Late Effects Cohort (RLEC) is a unique and irreplaceable population of aging NHP radiation survivors which serves the nation's need to understand the late effects of radiation exposure. Over the past 16 years, Wake Forest has evaluated > 250 previously irradiated rhesus macaques (Macaca mulatta) that were exposed to single total body irradiation (IR) doses of 1.14-8.5 Gy or to partial body exposures of up to 10 Gy (5% bone marrow sparing) or 10.75 Gy (whole thorax). Though primarily used to examine IR effects on disease-specific processes or to develop radiation countermeasures, this resource provides insights on resilience across physiologic systems and its relationship with biological aging. Exposure to IR has well documented deleterious effects on health, but the late effects of IR are highly variable. Some animals exhibit multimorbidity and accumulated health deficits, whereas others remain relatively resilient years after exposure to total body IR. This provides an opportunity to evaluate biological aging at the nexus of resilient/vulnerable responses to a stressor. Consideration of inter-individual differences in response to this stressor can inform individualized strategies to manage late effects of radiation exposure, and provide insight into mechanisms underlying systemic resilience and aging. The utility of this cohort for age-related research questions was summarized at the 2022 Trans-NIH Geroscience Interest Group's Workshop on Animal Models for Geroscience. We present a brief review of radiation injury and its relationship to aging and resilience in NHPs with a focus on the RLEC.

Assessment of Physical Resilience Using Residual Methods and Its Association With Adverse Outcomes in Older Adults

Background and Objectives

Physical resilience (PR) is recognized as the ability to recover from the adverse effects of a stressor. However, there is a lack of consensus on how to optimally measure PR in older adults in general. We aimed to measure PR using residuals from regression analyses and investigated its association with adverse outcomes in older adults.

Research Design and Methods

A total of 6 508 older adults were included from the National Health and Aging Trends Study, which was a population-based prospective cohort study. PR was assessed using residual methods from a linear model regressing the short physical performance battery on clinical diseases, age, sex, race/ethnicity, and health condition. Adverse outcomes included all-cause mortality, falls, and overnight hospitalization.

Results

The mean age was 77.48 (7.84) years. Increased PR was associated with a lower risk of all-cause mortality (hazard ratio [HR] = 0.85, 95% confidence interval [CI]: 0.83-0.87). Compared to participants with reduced PR, those with normal PR had a lower risk for mortality (HR = 0.51, 95% CI: 0.46-0.56). Specifically, restricted cubic spline regression revealed a dose-response relationship between PR and all-cause mortality (p-overall < .0001, p-nonlinear = .011). Additionally, we also found significant associations of increased PR with lower risks of falls (HR = 0.98, 95% CI: 0.96-0.99) and overnight hospitalization (HR = 0.98, 95% CI: 0.97-1.00).

Discussion and Implications

PR, measured by residual methods, was robustly and independently associated with all-cause mortality, falls, and overnight hospitalization. Our findings provide evidence that this approach may be a simple and feasible strategy to assess PR.

Frailty Resilience Score: A Novel Measure of Frailty Resilience Associated With Protection From Frailty and Survival

Frailty is characterized by increased vulnerability to disability and high risk for mortality in older adults. Identification of factors that contribute to frailty resilience is an important step in the development of effective therapies that protect against frailty. First, a reliable quantification of frailty resilience is needed. We developed a novel measure of frailty resilience, the Frailty Resilience Score (FRS), that integrates frailty genetic risk, age, and sex. Application of FRS to the LonGenity cohort (n = 467, mean age 74.4) demonstrated its validity compared to phenotypic frailty and its utility as a reliable predictor of overall survival. In a multivariable-adjusted analysis, 1-standard deviation increase in FRS predicted a 38% reduction in the hazard of mortality, independent of baseline frailty (p < .001). Additionally, FRS was used to identify a proteomic profile of frailty resilience. FRS was shown to be a reliable measure of frailty resilience that can be applied to biological studies of resilience.

Ageing and physical resilience after health stressors

The objectives of this article are to introduce a conceptual framework for physical resilience in the context of ageing and to discuss key elements and challenges in the design of studies of physical resilience after health stressors. Advancing age is associated with increasing exposure to multiple stressors and declining capacity to respond to health stressors. Resilience is defined broadly as the ability to resist or recover well from the adverse effects of a health stressor. In ageing-related study designs of physical resilience after a health stressor, this dynamic resilience response can be observed as changes in repeated measures of function or health status in various domains important to older adults. Methodologic issues in selecting the study population, defining the stressor, covariates, outcomes, and analytic strategies are highlighted in the context of an ongoing prospective cohort study of physical resilience after total knee replacement surgery. The article concludes with approaches to intervention development to optimize resilience.

Identifying predictors of resilience to stressors in single-arm studies of pre-post change

Many older adults experience a major stressor at some point in their lives. The ability to recover well after a major stressor is known as resilience. An important goal of geriatric research is to identify factors that influence resilience to stressors. Studies of resilience in older adults are typically conducted with a single-arm where everyone experiences the stressor. The simplistic approach of regressing change versus baseline yields biased estimates due to mathematical coupling and regression to the mean (RTM). We develop a method to correct the bias. We extend the method to include covariates. Our approach considers a counterfactual control group and involves sensitivity analyses to evaluate different settings of control group parameters. Only minimal distributional assumptions are required. Simulation studies demonstrate the validity of the method. We illustrate the method using a large, registry of older adults (N  =7239) who underwent total knee replacement (TKR). We demonstrate how external data can be utilized to constrain the sensitivity analysis. Naive analyses implicated several treatment effect modifiers including baseline function, age, body-mass index (BMI), gender, number of comorbidities, income, and race. Corrected analysis revealed that baseline (pre-stressor) function was not strongly linked to recovery after TKR and among the covariates, only age and number of comorbidities were consistently and negatively associated with post-stressor recovery in all functional domains. Correction of mathematical coupling and RTM is necessary for drawing valid inferences regarding the effect of covariates and baseline status on pre-post change. Our method provides a simple estimator to this end.

Mediating role of resilience in the relationships of physical activity and mindful self-awareness with peace of mind among college students

Peace of mind (PoM) is an index of mental health in Asian culture and emphasizes low arousal, happiness, harmony, and an internal state of peacefulness. While previous studies have found that mindful self-awareness can contribute to PoM, regular physical activity (PA) is also an important factor contributing to one's PoM due to its function in promoting one's resilience. The study aims to investigate a hypothetical model that assumes PA is associated with resilience while controlling for mindful self-awareness, contributing to PoM. The PoM scale, Connor-Davidson Resilience Scale, Chinese translation of Mindful Attention Awareness Scale, and PA self-report questionnaire were used. A path analysis was applied to test the association between these variables and the mediating role of resilience. A total of 436 students from a university in Taiwan were recruited; the mean age was 20.87, with 46.3% female and 73.6% engaging in over 150 min/week of moderate PA. Gender and age negatively correlated with PA. After controlling for age and gender, there was no direct effect of physical activity on PoM; both mindful self-awareness and PA predict resilience, which in turn predicts PoM, suggesting that both cognitive (i.e., mindful self-awareness) and PA are important to cultivate resilience and thus PoM.

Post-discharge light physical activity indicates recovery in acutely hospitalized older adults - the Hospital-ADL study

BACKGROUND

Physical activity (PA) levels might be a simple overall physical function indicator of recovery in acutely hospitalized older adults; however it is unknown which amount and level of PA is associated with recovery. Our objective was to evaluate the amount and level of post discharge PA and its optimum cut-off values associated with recovery among acutely hospitalized older adults and stratified for frailty.

METHODS

We performed a prospective observational cohort study including acutely hospitalized older adults (≥ 70 years). Frailty was assessed using Fried's criteria. PA was assessed using Fitbit up to one week post discharge and quantified in steps and minutes light, moderate or higher intensity. The primary outcome was recovery at 3-months post discharge. ROC-curve analyses were used to determine cut-off values and area under the curve (AUC), and logistic regression analyses to calculate odds ratios (ORs).

RESULTS

The analytic sample included 174 participants with a mean (standard deviation) age of 79.2 (6.7) years of whom 84/174 (48%) were frail. At 3-months, 109/174 participants (63%) had recovered of whom 48 were frail. In all participants, determined cut-off values were 1369 steps/day (OR: 2.7, 95% confidence interval [CI]: 1.3-5.9, AUC 0.7) and 76 min/day of light intensity PA (OR: 3.9, 95% CI: 1.8-8.5, AUC 0.73). In frail participants, cut-off values were 1043 steps/day (OR: 5.0, 95% CI: 1.7-14.8, AUC 0.72) and 72 min/day of light intensity PA (OR: 7.2, 95% CI: 2.2-23.1, AUC 0,74). Determined cut-off values were not significantly associated with recovery in non-frail participants.

CONCLUSIONS

Post-discharge PA cut-offs indicate the odds of recovery in older adults, especially in frail individuals, however are not equipped for use as a diagnostic test in daily practice. This is a first step in providing a direction for setting rehabilitation goals in older adults after hospitalization.

Social determinants of health and disease in companion dogs: a cohort study from the Dog Aging Project

Exposure to social environmental adversity is associated with health and survival across many social species, including humans. However, little is known about how these health and mortality effects vary across the lifespan and may be differentially impacted by various components of the environment. Here, we leveraged a relatively new and powerful model for human aging, the companion dog, to investigate which components of the social environment are associated with dog health and how these associations vary across the lifespan. We drew on comprehensive survey data collected on 21,410 dogs from the Dog Aging Project and identified five factors that together explained 33.7% of the variation in a dog's social environment. Factors capturing financial and household adversity were associated with poorer health and lower physical mobility in companion dogs, while factors that captured social support, such as living with other dogs, were associated with better health when controlling for dog age and weight. Notably, the effects of each environmental component were not equal: the effect of social support was 5× stronger than financial factors. The strength of these associations depended on the age of the dog, including a stronger relationship between the owner's age and the dog's health in younger as compared to older dogs. Taken together, these findings suggest the importance of income, stability and owner's age on owner-reported health outcomes in companion dogs and point to potential behavioral and/or environmental modifiers that can be used to promote healthy aging across species.

Re-examination of successful agers with lower biological than chronological age still after a 20-year follow-up period

BACKGROUND

Successful ageing is the term often used for depicting exceptional ageing but a uniform definition is lacking. The aim was to re-examine and describe the successful agers living at home at the age of 84 years or over after a 20-year follow-up. The purpose was also to identify possible factors leading to their successful ageing.

METHODS

Successful ageing was defined as the ability to live at home without daily care. Data on the participants' functional ability, objective health, self-rated health and satisfaction with life were gathered at baseline and after a 20-year follow-up period. A measurement of personal biological age (PBA) was established and the difference between the PBA and the chronological age (CA) was counted.

RESULTS

The participants' mean age was 87.6 years (Standard deviation 2.5, range 84-96). All analyzed variables depicted poorer physical ability and subjective health at re-examination than at baseline. Still, 99% of the participants were at least moderately satisfied with their lives. The PBA at baseline was 6.5 years younger than CA, and at re-examination, the difference was even more pronounced at 10.5 years.

DISCUSSION

Even though the participants were chronologically older, had poorer physical ability and subjective health, they were still satisfied with their lives indicating possible psychological resilience. The difference between the PBA and CA was greater at re-examination than at baseline indicating that they were also biologically successful agers.

CONCLUSIONS

Successful agers were satisfied with life despite hardships and had a lower biological than chronological age. Further research is needed to evaluate causality.

Intrinsic capacity and resilience: Taking frailty to the next level

In addition to frailty, two novel concepts have been introduced in the field of geriatrics to capture the heterogeneous ageing process: the first is intrinsic capacity, which uses a community-based, holistic approach and is propagated by the World Health Organization (WHO); and the second is resilience, which provides a more dynamic perspective on the individual's reserves, injury and recovery. While both concepts are linked to frailty, with all three focusing on reserves in relation to ageing, each approaches this issue from a different point of view. In this paper, we will compare and contrast these three concepts - frailty, intrinsic capacity and resilience - and assess their relevance to future geriatric oncology research as well as daily clinical practice.

Physical reserve: construct development and predictive utility

BACKGROUND

Physical reserve (PR) refers to one's ability to maintain physical functioning despite age, illness, or injury. The measurement and predictive utility of PR, however, are not well established.

AIMS

We quantified PR using a residual measurement approach by extracting standardized residuals from gait speed, while accounting for demographic and clinical/disease variables, and used it to predict fall-risk.

METHODS

Participants (n = 510; age ≥ 70ys) were enrolled in a longitudinal study. Falls were assessed annually (in-person) and bimonthly (via structured telephone interview).

RESULTS

General Estimating Equations (GEE) revealed that higher baseline PR was associated with reduced odds of reporting falls over repeated assessments in the total sample, and incident falls among those without fall's history. The protective effect of PR against fall risk remained significant when adjusting for multiple demographic and medical confounders.

DISCUSSION/CONCLUSION

We propose a novel framework to assessing PR and demonstrate that higher PR is protective against fall-risk in older adults.

New horizons in understanding oral health and swallowing function within the context of frailty

Frailty is a complex and multidimensional condition wherein declines in physiologic reserve and function place individuals in a state of heightened vulnerability and decreased resiliency. There has been growing interest in both research and clinical settings to understand how to best define, assess and characterise frailty in older adults. To this end, various models and clinical assessment tools have been used to define and measure frailty. While differences exist among these models and tools, a common unifying theme is a focus on physical function and activity. Notably absent across many available conceptual models and clinical tools are items directly related to oral and swallowing function. This is an important oversight as widespread changes to both oral and swallowing function are evident in older adults. Indeed, emerging evidence suggests many of the functional domains affected in frail older adults, such as nutrition and sarcopenia, have cyclical relationships with impairments in oral (oral hypofunction) and swallowing function (dysphagia) as well. The increasing appreciation for the interrelationships among oral hypofunction, dysphagia and frailty provides an opportunity for refinement of frailty assessment and characterisation in older adults to incorporate metrics specific to oral and swallowing function.

Physical activity is a potential measure of physical resilience in older adults receiving hemodialysis

Background

Physical resilience, or the ability to recover after a physical stressor, declines with aging. Efforts to preserve physical resilience in the older dialysis population are critically needed; however, validated, patient-centered measures that are sensitive to change are also needed. Our objective was to assess accelerometer-derived step count variability, or a measure of intra-individual variation in physical activity, as a potential measure of physical resilience among older adults receiving hemodialysis.

Methods

Community-dwelling ambulatory older adults receiving in-center hemodialysis were prospectively enrolled. Participants wore wrist accelerometers during daytime hours on both dialysis and non-dialysis days up to 14 days, and the feasibility of accelerometer use was assessed from wear time. We used accelerometer data to compute step counts in 4-hour blocks and step count variability. Physical function was assessed with the Short Physical Performance Battery (SPPB which includes gait speed test), grip strength, activities of daily living (ADLs) instruments, and life space mobility. We assessed interval fatigue (subjective rating from 0 to 10) on dialysis and non-dialysis days and self-reported recovery time. We assessed the correlations of step count variability with measures of physical function and step count and interval fatigue.

Results

Of 37 enrolled participants, 29 had sufficient accelerometer data for analyses. Among the 29 participants, mean (SD) age was 70.6(4.8) years, and 55% (n=16) were male and 72% (n=21) were Black race. Participants were largely sedentary with median (Q1-Q3) self-reported total kilocalories per week of 200 (36-552). Step count variability was positively correlated with measures of physical function: SPPB (r=0.50, p<0.05), gait speed (r=0.59, p<0.05), handgrip strength (r=0.71, p<0.05), Instrumental ADLs (r=0.44, p<0.05) and life space mobility (r=0.54, p<0.05).There was a weak inverse correlation between post-dialysis step counts (4-hour blocks after a dialysis session) and post-dialysis interval fatigue [r=-0.19 (n=102, p=0.06).

Conclusions

Physical activity assessment via accelerometer is feasible for older adults receiving hemodialysis. Step count variability correlated with physical function, so it may be a novel measure of physical resilience. Further studies are needed to validate this measure.

Reserve and resilience in CKD: concept introduction and baseline results from the Physical REsilience Prediction in Advanced REnal Disease (PREPARED) study

BACKGROUND

The purpose of this manuscript is to introduce reserve and resilience as novel concepts in chronic kidney disease (CKD) research and present baseline data from a unique prospective cohort study designed to characterize recovery from functional decline after a health event.

METHODS

The Physical REsilience Prediction in Advanced REnal Disease (PREPARED) study recruited a national, prospective cohort of Veterans ≥70 years old with an estimated glomerular filtration rate (eGFR) < 30 ml/min/1.73 m², prior nephrology care, and at high risk for hospitalization. Electronic health record data were paired with telephone surveys. Self-reported measures of reserve included physical, psychological, and cognitive capacity and environmental resources. We calculated counts (frequencies) and medians (25th, 75th percentiles) for baseline measures of reserve. The study's longitudinal follow-up of physical function every 8 weeks or following an acute care encounter, which will be used to define resilience, is ongoing.

RESULTS

Participants had a median (25th, 75th percentile) age of 76.3 (72.8, 81.4) years and eGFR of 23.4 (18.2, 28.8) ml/min/1.73 m²; 23.3% were Black, and 97.4% were male, 91.6% had hypertension, 67.4% had diabetes mellitus, 46.0% had coronary heart disease, and 39.8% had heart failure. Baseline measures of physical, psychological, and cognitive domains showed low reserve on average, but with wide ranges.

CONCLUSIONS

Despite similar levels of kidney function, older adults participating in PREPARED had a wide range of measures of reserve in other health domains. Non-renal measures of reserve may be important indicators of capacity of CKD patients to recover after acute care encounters.

Frailty does not cause all frail symptoms: United States Health and Retirement Study

BACKGROUND

Frailty is associated with major health outcomes. However, the relationships between frailty and frailty symptoms haven't been well studied. This study aims to show the associations between frailty and frailty symptoms.

METHODS

The Health and Retirement Study (HRS) is an ongoing longitudinal biannual survey in the United States. Three of the most used frailty diagnoses, defined by the Functional Domains Model, the Burden Model, and the Biologic Syndrome Model, were reproduced according to previous studies. The associations between frailty statuses and input symptoms were assessed using odds ratios and correlation coefficients.

RESULTS

The sample sizes, mean ages, and frailty prevalence matched those reported in previous studies. Frailty statuses were weakly correlated with each other (coefficients = 0.19 to 0.38, p < 0.001 for all). There were 49 input symptoms identified by these three models. Frailty statuses defined by the three models were not significantly correlated with one or two symptoms defined by the same models (p > 0.05 for all). One to six symptoms defined by the other two models were not significantly correlated with each of the three frailty statuses (p > 0.05 for all). Frailty statuses were significantly correlated with their own bias variables (p < 0.05 for all).

CONCLUSION

Frailty diagnoses lack significant correlations with some of their own frailty symptoms and some of the frailty symptoms defined by the other two models. This finding raises questions like whether the frailty symptoms lacking significant correlations with frailty statuses could be included to diagnose frailty and whether frailty exists and causes frailty symptoms.

Physical resilience in older adults: Potential use in promoting healthy aging

Physical resilience is a dynamic concept referring to the physiological response when the body is exposed to stressors. The level of physical resilience is the sum of underlying physiological reserves. Moreover, it may not only be determined by age, genetics, or exposure to a variety of diseases, but is also closely related to the psychological, social, and environmental factors of an individual. This paper summarizes our present understanding of the relationship between physical resilience and other concepts closely related to it. Furthermore, we illustrate the current research progress on physical resilience models and clinical resilience assessment. Besides, this paper intends to present a better understanding of physical resilience and its use in treatment decision-making, personalized diagnosis and disease management, and prevention and rehabilitation strategies.

Physical Resilience Phenotype Trajectories in Incident Hemodialysis: Characterization and Mortality Risk Assessment

Introduction

Methods

Results

Conclusion

Can the ECG be used to estimate age-related survival?

BACKGROUND

There are few reports of the relationship between electrocardiogram (ECG) findings and the age-related survival of acutely ill patients.

AIM

This study compared the 1-year survival curves of patients attending two Danish emergency departments (EDs) with normal and abnormal ECGs. Patients were divided into age groups from 20 to 90 years of age, and an abnormal ECG was defined as low QRS voltage (i.e. lead I + II <1.4 mV) or QTc interval prolongation >434 ms.

METHODS

A retrospective register-based observational study on 35 496 patients attending two Danish EDs, with 100% follow-up for 1 year.

RESULTS

ECG abnormality increases linearly with age, and between 30 and 70 years of age. Patients aged 20-29 years with ECG abnormalities are more than four times more likely to die within a year than patients of the same age with a normal ECG. An individual with an abnormal ECG has the same risk of dying within a year as an individual with a normal ECG who is 10 years older. After 70 years of age this tight relationship ends, but for younger individuals with an abnormal ECG the increase in mortality is even higher.

CONCLUSION

An ECG may be a simple practical estimate of age-related survival. For a patient under 70 years, an abnormal QRS voltage or a prolonged QTc interval may increase 1-year mortality to that of a patient ∼10 years older.

Physiological Systems in Promoting Frailty

Frailty is a complex syndrome affecting a growing sector of the global population as medical developments have advanced human mortality rates across the world. Our current understanding of frailty is derived from studies conducted in the laboratory as well as the clinic, which have generated largely phenotypic information. Far fewer studies have uncovered biological underpinnings driving the onset and progression of frailty, but the stage is set to advance the field with preclinical and clinical assessment tools, multiomics approaches together with physiological and biochemical methodologies. In this article, we provide comprehensive coverage of topics regarding frailty assessment, preclinical models, interventions, and challenges as well as clinical frameworks and prevalence. We also identify central biological mechanisms that may be at play including mitochondrial dysfunction, epigenetic alterations, and oxidative stress that in turn, affect metabolism, stress responses, and endocrine and neuromuscular systems. We review the role of metabolic syndrome, insulin resistance and visceral obesity, focusing on glucose homeostasis, adenosine monophosphate-activated protein kinase (AMPK), mammalian target of rapamycin (mTOR), and nicotinamide adenine dinucleotide (NAD⁺ ) as critical players influencing the age-related loss of health. We further focus on how immunometabolic dysfunction associates with oxidative stress in promoting sarcopenia, a key contributor to slowness, weakness, and fatigue. We explore the biological mechanisms involved in stem cell exhaustion that affect regeneration and may contribute to the frailty-associated decline in resilience and adaptation to stress. Together, an overview of the interplay of aging biology with genetic, lifestyle, and environmental factors that contribute to frailty, as well as potential therapeutic targets to lower risk and slow the progression of ongoing disease is covered. © 2022 American Physiological Society. Compr Physiol 12:1-46, 2022.

Development and psychometric evaluation of the Physical Resilience Instrument for Older Adults (PRIFOR)

Background

Physical resilience is known to minimize the adverse outcomes of health stressors for older people. However, validated instruments that assess physical resilience in older adults are rare. Therefore, we aimed to validate the Physical Resilience Instrument for Older Adults (PRIFOR) to fill the literature gap.

Methods

Content analysis with content validity was first carried out to generate relevant items assessing physical resilience for older adults, and 19 items were developed. Psychometric evaluation of the 19 items was then tested on 200 older adults (mean [SD] age = 76.4 [6.6] years; 51.0% women) for item properties, factor structure, item fit, internal consistency, criterion-related validity, and known-group validity.

Results

All 19 items had satisfactory item properties, as they were normally distributed (skewness = -1.03 to 0.38; kurtosis = -1.05 to 0.32). However, two items were removed due to substantial ceiling effects. The retained 17 items were embedded in three factors as suggested by the exploratory factor analysis (EFA) results. All items except one had satisfactory item fit statistics in Rasch model; thus, the unidimensionality was supported for the three factors on 16 items. The retained 16 items showed promising properties in known-group validity, criterion-related validity, and internal consistency (α = 0.94).

Conclusions

The 16-item PRIFOR exhibits good psychometric properties. Using this instrument to measure physical resilience would be beneficial to identify factors that could protect older people from negative health consequence. With the use of the PRIFOR, intervention effects could also be evaluated. It is helpful to strengthen resilience and thereby facilitate successful aging.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12877-022-02918-7.

Bridging the Gap: A Geroscience Primer for Neuroscientists With Potential Collaborative Applications

While neurodegenerative diseases can strike at any age, the majority of afflicted individuals are diagnosed at older ages. Due to the important impact of age in disease diagnosis, the field of neuroscience could greatly benefit from the many of the theories and ideas from the biology of aging-now commonly referred as geroscience. As discussed in our complementary perspective on the topic, there is often a "silo-ing" between geroscientists who work on understanding the mechanisms underlying aging and neuroscientists who are studying neurodegenerative diseases. While there have been some strong collaborations between the biology of aging and neuroscientists, there is still great potential for enhanced collaborative effort between the 2 fields. To this end, here, we review the state of the geroscience field, discuss how neuroscience could benefit from thinking from a geroscience perspective, and close with a brief discussion on some of the "missing links" between geroscience and neuroscience and how to remedy them. Notably, we have a corresponding, concurrent review from the neuroscience perspective. Our overall goal is to "bridge the gap" between geroscience and neuroscience such that more efficient, reproducible research with translational potential can be conducted.

Frailty and In-Hospital Mortality Risk Using EHR Nursing Data

PurposeThe purpose of this study was to evaluate four definitions of a Frailty Risk Score (FRS) derived from EHR data that includes combinations of biopsychosocial risk factors using nursing flowsheet data or International Classification of Disease, 10th revision (ICD-10) codes and blood biomarkers and its predictive properties for in-hospital mortality in adults ≥50 years admitted to medical-surgical units. Methods In this retrospective observational study and secondary analysis of an EHR dataset, survival analysis and Cox regression models were performed with sociodemographic and clinical covariates. Integrated area under the ROC curve (iAUC) across follow-up time based on Cox modeling was estimated. Results The 46,645 patients averaged 1.5 hospitalizations (SD = 1.1) over the study period and 63.3% were emergent admissions. The average age was 70.4 years (SD = 11.4), 55.3% were female, 73.0% were non-Hispanic White (73.0%), mean comorbidity score was 3.9 (SD = 2.9), 80.5% were taking 1.5 high risk medications, and 42% recorded polypharmacy. The best performing FRS-NF-26-LABS included nursing flowsheet data and blood biomarkers (Adj. HR = 1.30, 95% CI [1.28, 1.33]), with good accuracy (iAUC = .794); the reduced model with age, sex, and FRS only demonstrated similar accuracy. The poorest performance was the ICD-10 code-based FRS. Conclusion The FRS captures information about the patient that increases risk for in-hospital mortality not accounted for by other factors. Identification of frailty enables providers to enhance various aspects of care, including increased monitoring, applying more intensive, individualized resources, and initiating more informed discussions about treatments and discharge planning.

Physical Resilience in Daily Functioning Among Acutely Ill Hospitalized Older Adults: The Hospital-ADL Study

OBJECTIVES

Insight into older adults' physical resilience is needed to predict functional recovery after hospitalization. We assessed functional trajectories in response to acute illness and subsequent hospitalization and investigated baseline variables and dynamic variables associated with these trajectories.

DESIGN

Prospective observational cohort study (Hospitalization-Associated Disability and impact on daily Life Study).

SETTING AND PARTICIPANTS

This study included 207 older adults (aged 79.8 ± 6.9 years, 49% female, 57% frail) acutely hospitalized in 6 Dutch hospitals.

METHODS

Functional disability was assessed using the 15-item modified activities of daily living index retrospectively 2 weeks before admission, and prospectively from admission up to 3 months after discharge. Baseline variables including frailty, somatic, physical, and psychosocial factors were assessed at admission. Dynamic variables (step count, pain, fatigue, and fear of falling) were continuously or repeatedly assessed during hospitalization. We performed individual spline modeling using random effects. Baseline variables and within-person mean levels and variability in the dynamic variables were assessed as predictors of functional trajectories.

RESULTS

Functional disability significantly increased before admission and decreased from admission to 3 months post discharge. Frail participants had a significantly higher increase in functional disability before admission compared with nonfrail participants. Lower step count, higher pain scores, and higher within-person variability in fear of falling were significantly associated with higher increase in functional disability before admission. Higher within-person variability in fear of falling was associated with more recovery.

CONCLUSIONS AND IMPLICATIONS

Older adults increase in functional disability before hospitalization and start to recover from admission onward. Frailty and dynamic variables are associated with a higher increase in functional disability after acute illness. Our findings give more insight into older adults' physical resilience, which may improve the prediction of functional recovery and may improve therapeutic decision-making and rehabilitation strategies to improve functional recovery after acute hospitalization.

Perceived Recovery Time from Common Cold as a Possible Indicator of Physical Resilience

Background

Resilience refers to the ability to recover function after encounter with stressors. While psychological resilience refers to the ability to cope with psychological stress, physical resilience refers to functional restoration after biomedical challenges. However, there is no gold standard to assess physical resilience. Accordingly, we explored whether the perceived recovery time from common cold could be used to represent physical resilience.

Methods

We analyzed data of individuals aged 72–86 years who had participated in the Korean Frailty and Aging Cohort Study in 2019. Among the 1,455 survey participants, 594 with asthma and chronic obstructive pulmonary disease and missing data were excluded. The remaining 861 participants were divided into three groups according to the number of days required for recovery from common cold (Group 1, 1–4 days; Group 2, 5–7 days; and Group 3, ≥8 days). The relationship between recovery time and psychological resilience scale (Brief Resilience Scale [BRS]) score, physical frailty (Fried’s physical frailty phenotype and the Korean Frailty Index for Primary Care [KFI-PC]), and frailty outcome was investigated.

Results

Group 3 comprised individuals more likely to be women, sleep less, be less physically less active, fall more often, and have a low EuroQol visual analogue scale score. BRS scores differed significantly among the three groups (Group 1, 13.29; Group 2, 14.32; Group 3, 15.22; p<0.001). In multivariate analysis, post-hoc analysis with the Bonferroni method revealed significant differences in BRS between Groups 1–2 and Groups 1–3. However, the KFI-PC and number of falls did not differ significantly.

Conclusions

Longer days of recovery from cold were associated with worse BRS scores. However, neither frailty nor the number of falls was related.

A template for physical resilience research in older adults: Methods of the PRIME-KNEE study

BACKGROUND

Older adults with similar health conditions often experience widely divergent outcomes following health stressors. Variable recovery after a health stressor may be due in part to differences in biological mechanisms at the molecular, cellular, or system level, that are elicited in response to stressors. We describe the PRIME-KNEE study as an example of ongoing research to validate provocative clinical tests and biomarkers that predict resilience to specific health stressors.

METHODS

PRIME-KNEE is an ongoing, prospective cohort study that will enroll 250 adults ≥60 years undergoing total knee arthroplasty. Data are collected at baseline (pre-surgery), during surgery, daily for 7 days after surgery, and at 1, 2, 4, and 6 months post-surgery. Provocative tests include a cognition-motor dual-task walking test, cerebrovascular reactivity assessed by functional near-infrared spectroscopy, peripheral blood mononuclear cell reactivity ex vivo to lipopolysaccharide toxin and influenza vaccine, and heart rate variability during surgery. Cognitive, psychological, and physical performance batteries are collected at baseline to estimate prestressor reserve. Demographics, medications, comorbidities, and stressor characteristics are abstracted from the electronic medical record and via participant interview. Blood-based biomarkers are collected at baseline and postoperative day 1. Repeated measures after surgery include items from a delirium assessment tool and pain scales administered daily by telephone for 7 days and cognitive change index (participant and informant), lower extremity activities of daily living, pain scales, and step counts assessed by Garmin actigraphy at 1, 2, 4, and 6 months after surgery. Statistical models use these measures to characterize resilience phenotypes and evaluate prestressor clinical indicators associated with poststressor resilience.

CONCLUSION

If PRIME-KNEE validates feasible clinical tests and biomarkers that predict recovery trajectories in older surgical patients, these tools may inform surgical decision-making, guide pre-habilitation efforts, and elucidate mechanisms underlying resilience. This study design could motivate future geriatric research on resilience.

Adherence to the Mediterranean Diet and Physical Resilience in Older Adults: The Seniors-ENRICA Cohort

BACKGROUND

No prior studies have studied the association between diet and physical resilience, thus our aim was to assess the association between the adherence to the Mediterranean diet and other healthy dietary patterns and physical resilience, assessed empirically as a trajectory through exposure to chronic and acute stressors, in older adults participating in the Seniors-ENRICA (The Study on Nutrition and Cardiovascular Risk in Spain) cohort.

METHODS

Data were assessed from 1301 individuals aged 60 and older, participating in the ENRICA prospective cohort study and recruited in 2008-2010 and followed up to 2012 (trial registration: NCT02804672). A Mediterranean Diet Adherence Screener score and the Alternate Healthy Eating Index 2010 were derived at baseline from a validated diet history. Health status was assessed at baseline and at the end of follow-up with a 52-item health Deficit Accumulation Index (DAI) including 4 domains (physical and cognitive function, mental health, self-rated health/vitality, and morbidity); higher DAI values indicate worse health. Physical resilience was defined as accumulating fewer health deficits than the expected age-related increase in DAI over follow-up, despite exposure to chronic and acute stressors.

RESULTS

Over a 3.2-year follow-up, 610 individuals showed physical resilience. In multivariate analyses, the odds ratio (95% confidence interval) of physical resilience for the highest versus lowest tertile (lowest adherence) of the Mediterranean Diet Adherence Screener score was 1.47 (1.10-1.98). The association held for those maintaining or improving the DAI over follow-up (over-resilience): 1.58 (1.10-2.26). Results were consistent in those with unintentional weight loss (2.21 [1.10-4.88]) or hospitalization (2.32 [1.18, 4.57]) as acute stressors.

CONCLUSION

In older adults, a higher adherence to the Mediterranean diet is associated with a greater likelihood of physical resilience.

Principles and Issues for Physical Frailty Measurement and Its Clinical Application

INTRODUCTION

"Frailty" has attracted attention for its promise of identifying vulnerable older adults, hence its potential use to better tailor geriatric health care. There remains substantial controversy, however, regarding its nature and ascertainment. Recent years have seen a proliferation of frailty assessment methods. We argue that the development of frailty assessments should be grounded in "validation"-the process of substantiating that a measurement accurately and precisely measures what it intends, identify unresolved measurement issues, and highlight measurement-related considerations for clinical practice.

METHODS

Principles for validating frailty measures are elucidated. We follow principles-articulated, for example, by Borsboom-in which a construct must be clearly defined and then analyses undertaken to substantiate that a measurement accurately and precisely measures what it intends. Key elements are content validity, criterion validity, and construct validity, with an emphasis on the latter.

RESULTS

We illustrate the principles for a physical frailty phenotype construct.

CONCLUSIONS

Unresolved conceptual issues include the roles of intersecting concepts such as cognition, disease severity, and disability in frailty measurement, conceptualization of frailty as a state versus a continuum, and the potential need for dynamic measures and systems concepts in furthering understanding of frailty. Clinical considerations include needs to distinguish interventions designed to address frailty "symptoms" versus underlying physiology, improve "prefrailty" measures intended to screen individuals early in their frailty progression, address feasibility demands, and further visioning followed by rigorous efficacy research to address the landscape of potential uses of frailty assessment in clinical practice.

Predictive Validity of the Physical Resilience Instrument for Older Adults (PRIFOR)

This study aimed at evaluating the predictive ability of the Physical Resilience Instrument for Older Adults (PRIFOR) for the recovery of frailty, activity of daily living (ADL), and quality of life in older adults suffering from acute health stressors. The longitudinal study was adopted and patients aged 65 and older with Clinical Frailty Scale (CFS) scores between 4 and 6 were included. The PRIFOR was used to assess physical resilience at baseline. Katz ADL, CFS and EuroQoL 5-dimension Questionnaire (EQ5D) scores were all assessed at baseline and one month after discharge. The mean age of the 192 participants was 76.29 ± 6.53 years, and 50.5% were female. After adjusting for the baseline condition, the PRIFOR was only significantly associated with the CFS (β=-0.183, p<0.001) at one month after discharge. Our study results provide evidence of the predictive capacity of the PRIFOR for recovery from frailty.

Intrinsic Capacity as a Determinant of Physical Resilience in Older Adults

The traditional disease-oriented model of healthcare is inadequate to address the needs of the older population. Greater attention should be given to strategies that promote healthy aging. Recently proposed constructs of intrinsic capacity (IC) and physical resilience (PR) hold great potential to reshape geriatric medicine and aging research. These constructs accentuate the positive health attributes of older people in contrast to the popular frailty construct that is centered on functional deficits. IC was introduced by the World Health Organization (WHO) as a composite of all the physical and mental capacities. WHO has emphasized enhancement of IC throughout the life course so as to maintain functional ability in old age. PR, recently highlighted by the National Institute on Aging, is the ability to successfully cope with stressors. High levels of resilience can result in desirable clinical and functional outcomes after stressors. Therefore, it is important to understand the underlying physiology of PR and the risk factors contributing to diminished PR. The main goal of this article is to explore the potential relationship between IC and PR. Based on a classical theory of aging, we postulate that IC is a determinant of PR and is also a high-level integrative measure of physiologic reserve which is the fundamental factor underlying one's ability to withstand stressors. A major implication of our postulates is that even though IC is only one of the many determinants of PR, it could serve as an important intervenable target for enhancing resilience in older adults.

Plasma levels of corticosterone, tumor necrosis factor receptor 1 and interleukin 6 are influenced by age, sex and chronic inflammation in mice treated with acute temperature stress

Resiliency is the ability to respond to, adapt to and recover from stressors. Deterioration of resiliency in older adults has been hypothesized to be regulated by age-related changes in stress response systems, including the Hypothalamic Pituitary Adrenal (HPA) axis and the innate immune system response. Although age-related chronic inflammation is strongly related to lack of resiliency, the impact of chronic inflammation on acute stress response is unclear. Here we describe the impact of a five-hour exposure to cold temperature acute stressor, on immune and corticosterone response using older and younger IL-10^tm/tm mice, a mouse model with chronic inflammatory pathway activation, and age and gender matched C57/Bl6 background control (WT) mice. Overall, mice exposed to 4 °C for 5 h had significantly higher plasma corticosterone levels compared to those that remained at room temperature (25 °C), with the exception of the WT females. Cold stressed mice had lower plasma tumor necrosis factor receptor 1 (TNFR1) levels with varying significance, in all ages and phenotypes, with the exception of the old female WT mice. In contrast, the effects of cold stress on pro-inflammatory cytokine interleukin 6 (IL-6) levels were inconsistent and not significant, with the exception of the female IL-10^tm/tm mice. In conclusion, these findings demonstrate that sex, age and chronic inflammatory pathway activation all influence corticosterone secretion and inflammatory processes in the face of acute cold stress.

The geroscience agenda: Toxic stress, hormetic stress, and the rate of aging

Geroscience offers a counterpoint to the challenged pursuit of curing diseases of aging, by focusing on slowing the biological aging process for extended healthspan earlier in life. Remarkable progress has led this field toward animal trials and the next challenge lies with translation to humans. There is an emerging number of small human trials that can take advantage of new models integrating behavioral and social factors. Understanding dynamic aging mechanisms, given the powerful social determinants of aging (Crimmins, 2020) and human variability and environmental contexts (Moffitt, 2020), will be critical. Behavioral and social factors are intrinsic to aging. Toxic stressors broadly defined can lead to stress-acceleration of aging, either directly impacting aging processes or by shaping poor behavioral health, and underlie the socioeconomic disparities of aging. In contrast, hormetic stressors, acute intermittent stressors of moderate intensity, can produce stress resilience, the ability for quick recovery and possibly rejuvenation of cells and tissues. Although health research usually examines static biomarkers, aging is reflected in dynamic ability to recover from challenges pointing to new interventions and targets for examining mechanisms. A fuller model incorporating stress resilience provides innovative biobehavioral interventions, both for bolstering response to challenges, such as COVID-19, and for improving healthspan.

What Now for Rehabilitation Specialists? Coronavirus Disease 2019 Questions and Answers

Recognizing a need for more guidance on the coronavirus disease 2019 (COVID-19) pandemic, members of the Archives of Physical Medicine and Rehabilitation Editorial Board invited several clinicians with early experience managing the disease to collaborate on a document to help guide rehabilitation clinicians in the community. This consensus document is written in a “question and answer” format and contains information on the following items: common manifestations of the disease; rehabilitation recommendations in the acute hospital setting, recommendations for inpatient rehabilitation and special considerations. These suggestions are intended for use by rehabilitation clinicians in the inpatient setting caring for patients with confirmed or suspected COVID-19. The text represents the authors’ best judgment at the time it was written. However, our knowledge of COVID-19 is growing rapidly. The reader should take advantage of the most up-to-date information when making clinical decisions.

Biomarkers Associated with Physical Resilience After Hip Fracture

BACKGROUND

Clinically similar older adults demonstrate variable responses to health stressors, heterogeneity attributable to differences in physical resilience. However, molecular mechanisms underlying physical resilience are unknown. We previously derived a measure of physical resilience after hip fracture-the expected recovery differential (ERD)-that captures the difference between actual recovery and predicted recovery. Starting with biomarkers associated with physical performance, morbidity, mortality, and hip fracture, we evaluated associations with the ERD to identify biomarkers of physical resilience after hip fracture.

METHODS

In the Baltimore Hip Studies (N = 304) sera, we quantified biomarkers of inflammation (TNFR-I, TNFR-II, sVCAM-1, and IL-6), metabolic and mitochondrial function (non-esterified fatty acids, lactate, ketones, acylcarnitines, free amino acids, and IGF-1), and epigenetic dysregulation (circulating microRNAs). We used principal component analysis, canonical correlation, and least absolute shrinkage and selection operator regression (LASSO) to identify biomarker associations with better-than-expected recovery (greater ERD) after hip fracture.

RESULTS

Participants with greater ERD were more likely to be women and less disabled at baseline. The complete biomarker set explained 37% of the variance in ERD (p < .001) by canonical correlation. LASSO regression identified a biomarker subset that accounted for 27% of the total variance in the ERD and included a metabolic factor (aspartate/asparagine, C22, C5:1, lactate, glutamate/mine), TNFR-I, miR-376a-3p, and miR-16-5p.

CONCLUSIONS

We identified a set of biomarkers that explained 27% of the variance in ERD-a measure of physical resilience after hip fracture. These ERD-associated biomarkers may be useful in predicting physical resilience in older adults facing hip fracture and other acute health stressors.