Dual cognitive and mobility impairments and future dementia - Setting a research agenda

Dual cognitive and mobility impairments are associated with an increased risk of dementia. Recent studies examining temporal trajectories of mobility and cognitive function in aging found that dual decline is associated with higher dementia risk than memory decline or gait decline only. Although initial data show that individuals with dual decline or impairment have excessive cardiovascular and metabolic risk factors, the causes of dual decline or what underlies dual decline with a high risk of dementia remain largely unknown. In December 2021, the National Institute on Aging Intramural and Extramural Programs jointly organized a workshop on Biology Underlying Moving and Thinking to explore the hypothesis that older persons with dual decline may develop dementia through a specific pathophysiological pathway. The working group discussed assessment methods for dual decline and possible mechanisms connecting dual decline with dementia risk and pinpointed the most critical questions to be addressed from a translational perspective.

Concurrent Validity Between Potential Screening Tests for Early Mobility Decline in Independent Community Dwellers

BACKGROUND AND PURPOSE

Standardized screening tests that detect early mobility decline, regardless of etiology, are needed for healthy aging. The locomotive syndrome (LS) tests are designed to identify stages of mobility decline and inform appropriate levels of intervention. The long-term goal of this research is to develop standardized mobility screening tests that can be used across health care settings and throughout a patient's lifespan to guide appropriate medical care. As the first step in this process, this study examines the concurrent validity between the reference and the LS tests.

METHODS

This cross-sectional study examined correlations between the LS functional tests and a set of reference tests and the ability to differentiate the 3 stages of mobility decline. The reference tests included the stair-climbing test, the 30-second chair rise test, the 6-minute walk test, the Global Physical Health (GPH) portion of the PROMIS, and the Lower Extremity Functional Scale (LEFS). The LS tests included the Stand-Up Test, the 2-Step Test, and the 25-question Geriatric Locomotive Function Scale (25-GLFS). A total of 115 community dwellers of 61.2 years old on average (±10.0 years), with n = 71 (61%) older than 60 years, voluntary participated in this prospective study. Nonparametric analyses of variance and correlations were used to examine the concurrent validity.

RESULTS AND DISCUSSION

Performance-based tests were significantly correlated (| r | = 0.38-0.61, P < .001) with LS tests. The LEFS was correlated with all LS tests, but the GPH was only correlated with the 25-GLFS. Also, significant differences were found in reference test scores between the 3 LS stages ( P < .05).

CONCLUSIONS

The LS tests and reference tests demonstrated significant correlations, and participants performed significantly worse on reference tests as LS severity increased. Given these results, it is possible that the LS standardized tests may play an important role in mobility screening. Future research should investigate feasibility, sensitivity, and specificity of these tests.

Muscle mitochondrial energetics predicts mobility decline in well-functioning older adults: The baltimore longitudinal study of aging

Background

Muscle mitochondrial dysfunction is associated with poor mobility in aging. Whether mitochondrial dysfunction predicts subsequent mobility decline is unknown.

Methods

We examined 380 cognitively normal participants aged 60 and older (53%women, 22%Black) who were well‐functioning (gait speed ≥ 1.0 m/s) and free of Parkinson's disease and stroke at baseline and had data on baseline skeletal muscle oxidative capacity and one or more mobility assessments during an average 2.5 years. Muscle oxidative capacity was measured by phosphorus magnetic resonance spectroscopy as the post‐exercise recovery rate of phosphocreatine (k_PCr). Mobility was measured by four walking tests. Associations of baseline k_PCr with mobility changes were examined using linear mixed‐effects models, adjusted for covariates. In a subset, we examined whether changes in muscle strength and mass affected these associations by adjusting for longitudinal muscle strength, lean mass, and fat mass.

Results

Lower baseline k_PCr was associated with greater decline in all four mobility measures (β, p‐value: (0.036, 0.020) 6‐m usual gait speed; (0.029, 0.038) 2.5‐min usual gait speed; (0.034, 0.011) 6‐m rapid gait speed; (−0.042, <0.001) 400‐m time). In the subset, further adjustment for longitudinal muscle strength, lean mass, and fat mass attenuated longitudinal associations with changes in mobility (Δβ reduced 26–63%).

Conclusion

Among initially well‐functioning older adults, worse muscle mitochondrial function predicts mobility decline, and part of this longitudinal association is explained by decline in muscle strength and mass. Our findings suggest that worse mitochondrial function contributes to mobility decline with aging. These findings need to be verified in studies correlating longitudinal changes in mitochondrial function, muscle, and mobility performance.

Depression and Functional Mobility Decline in Long Term Care Home Residents with Dementia: a Prospective Cohort Study

Objective

Assess the association between depression among new long-term care residents (<3 months stay) with dementia and functional mobility decline.

Methods

A multi-site prospective cohort study was carried out among 26 participants diagnosed with dementia. Functional mobility was measured by Timed-Up-and-Go (TUG) and 2-Minute walk test (2MWT) at baseline, and 60-day post-baseline while participants received usual care. Linear mixed models were applied to examine the association between depression and functional mobility decline.

Results

Residents experienced a statistically significant decline in functional mobility in as soon as 60 days. Each additional year of age was associated with a 2% increase in TUG. The interaction between depression and time spent in LTC was statistically significant. Age and time living in LTC were significantly associated with functional mobility decline in new residents with dementia.

Discussion

Further work determining why residents with dementia experience decline in functional mobility at an accelerated rate is needed.

SART and Individual Trial Mistake Thresholds: Predictive Model for Mobility Decline

The Sustained Attention to Response Task (SART) has been used to measure neurocognitive functions in older adults. However, simplified average features of this complex dataset may result in loss of primary information and fail to express associations between test performance and clinically meaningful outcomes. Here, we describe a new method to visualise individual trial (raw) information obtained from the SART test, vis-à-vis age, and groups based on mobility status in a large population-based study of ageing in Ireland. A thresholding method, based on the individual trial number of mistakes, was employed to better visualise poorer SART performances, and was statistically validated with binary logistic regression models to predict mobility and cognitive decline after 4 years. Raw SART data were available for 4864 participants aged 50 years and over at baseline. The novel visualisation-derived feature bad performance, indicating the number of SART trials with at least 4 mistakes, was the most significant predictor of mobility decline expressed by the transition from Timed Up-and-Go (TUG) < 12 to TUG ≥ 12 s (OR = 1.29; 95% CI 1.14–1.46; p < 0.001), and the only significant predictor of new falls (OR = 1.11; 95% CI 1.03–1.21; p = 0.011), in models adjusted for multiple covariates. However, no SART-related variables resulted significant for the risk of cognitive decline, expressed by a decrease of ≥2 points in the Mini-Mental State Examination (MMSE) score. This novel multimodal visualisation could help clinicians easily develop clinical hypotheses. A threshold approach to the evaluation of SART performance in older adults may better identify subjects at higher risk of future mobility decline.

Pittsburgh Fatigability Scale: One-Page Predictor of Mobility Decline in Mobility-Intact Older Adults

OBJECTIVES

To evaluate the Pittsburgh Fatigability Scale (PFS) as a predictor of performance and functional decline in mobility-intact older adults.

DESIGN

Longitudinal analysis of Baltimore Longitudinal Study of Aging data.

SETTING

National Institute on Aging, Clinical Research Unit, Baltimore, Maryland.

PARTICIPANTS

Mobility-intact men (46.8%) and women aged 60 to 89 with concurrent PFS administration and performance and functional assessment and follow-up assessment within 1 to 4 years (N=579).

MEASUREMENTS

The PFS is a self-administered, 1-page assessment of expected physical and mental fatigue with a score ranging from 0 (no) to 5 (extreme) associated with performing 10 activities. Analyses examined associations between each dimension scored continuously (0-50), categorically (0-5), and dichotomously and change in and likelihood of clinically meaningful decline in usual and fast gait speed, chair stand pace, and reported walking ability. Covariates included age, age² , sex, race, visit status, baseline function, and follow-up time. We defined meaningful decline as 0.05 m/s per year for usual gait speed, 0.07 m/s per year for fast gait speed, 0.02 chair stands/s per year and 1 point or more for walking ability index.

RESULTS

Over a mean 2.2 years, 20.5% to 37.7% of participants experienced meaningful decline across assessments. Independent of covariates, higher PFS physical and mental scores were most consistently associated with greater decline in usual gait speed, chair stand pace, and reported walking ability regardless of scoring approach. For example, higher physical fatigability was associated with twice the likelihood of meaningful decline in gait speed as lower physical fatigability (p=.001). PFS scores were superior to fatigue symptoms such as tiredness and energy level in predicting performance decline, which showed no association.

CONCLUSION

Routine self-administered perceived fatigability assessment may help identify older persons vulnerable to accelerated mobility decline. J Am Geriatr Soc 66:2092-2096, 2018.

Fatigued, but Not Frail: Perceived Fatigability as a Marker of Impending Decline in Mobility-Intact Older Adults

OBJECTIVES

To evaluate perceived fatigability as a predictor of meaningful functional decline in non-mobility-limited older adults.

DESIGN

Longitudinal analysis of data from the Baltimore Longitudinal Study of Aging (BLSA).

SETTING

National Institute on Aging, Clinical Research Unit, Baltimore, Maryland.

PARTICIPANTS

Men and women aged 60 to 89 participating in the BLSA with concurrent perceived fatigability and functional assessments and follow-up functional assessment within 1 to 3 years (N = 540).

MEASUREMENTS

Perceived fatigability was ascertained using the Borg rating of perceived exertion (RPE) after 5 minutes of treadmill walking at 1.5 miles per hour. Functional assessments included usual and fast gait speed, the Health, Aging and Body Composition physical performance battery (HABC PPB) and reported walking ability. Reported tiredness and energy level were examined as complementary predictors. Covariates included age, age squared, race, follow-up time, and baseline function. Meaningful decline was defined as 0.05 m/s per year for usual gait speed, 0.07 m/s per year for fast gait speed, 0.12 points/year for HABC PPB, and 1 point for walking ability index.

RESULTS

Over a mean 2.1 years, 20-31% of participants declined across functional assessments. Fatigability was associated with a 13-19% greater likelihood of meaningful decline in all measures (P = .002- .02) per 1-unit RPE increase. After considering tiredness and energy level separately, findings were essentially unchanged, and neither was associated with gait speed or physical performance decline. In contrast, each separately predicted decline in reported walking ability independent of fatigability (P = .03 and P < .001, respectively).

CONCLUSION

Routine assessment of fatigability may help identify older persons vulnerable to greater-than-expected functional decline.

Absolute strength and loss of strength as predictors of mobility decline in older adults: the InCHIANTI study

BACKGROUND

Theoretical definitions of sarcopenia traditionally emphasize age-related loss of muscle strength; however, most analyses of the association between strength and mobility examine strength at a single time point. This study sought to identify sex-specific cutpoints for muscle strength and power (at one time point) and 3-year changes in strength and power that would maximize prediction of 3-year mobility decline.

METHODS

Longitudinal analysis of 934 adults aged ≥65 years enrolled in the Invecchiare in Chianti study was conducted. Grip strength, knee extension strength, and lower extremity power were measured at baseline and 3 years postenrollment. Mobility function (gait speed and self-reported mobility disability) was measured at 3 and 6 years postenrollment. Classification and regression tree analysis was used to predict mobility decline from Years 3 to 6.

RESULTS

Men with knee extension strength <19.2 kg and grip strength <39.0 kg had clinically meaningful declines in gait speed of .24 m/s. Furthermore, men with power <105 W were nearly nine times more likely to develop incident mobility disability (likelihood ratio = 8.68; 95% confidence interval = 3.91, 19.44). Among women, knee extension strength <18.0 kg was associated with a minimal gait speed decline of 0.06 m/s, and women with leg power <64 W were three times more likely to develop incident mobility disability (likelihood ratio = 3.01; 95% confidence interval = 1.79, 5.08). Three-year changes in strength and power did not predict mobility decline in either sex.

CONCLUSIONS

Findings suggest that strength and power measured at one time point are more predictive of mobility decline than 3-year changes and that low strength and power are particularly powerful risk factors in men.