Covariates:

• Minimally adjusted model: age, height, sex, race, length of follow up (longitudinal only), baseline physical performance (longitudinal only) • Fully adjusted model: adds weight, physical activity level, diabetes status

METHODS

SUMMARY & CONCLUSION

INTRODUCTION

• It was hypothesized that, since the neurological and muscular systems are closely intertwined, neurological function would predict poorer mobility and accelerated decline. • If this is true, neurological testing could be used to assess risk for impaired mobility and allow for earlier intervention and delayed decline. • The objective was to identify which, if any, aspects of neurological function indicate the presence of or predict future impaired mobility in older adults.

• This study used data from the Baltimore Longitudinal Study of Aging (BLSA). • Started in 1958, the BLSA is the longest running scientific research study on aging in the country. • The research conducted is longitudinal and purely observational. • The participants analyzed in this study were at least 60 years of age. Those from age 60 to 80 visit the BLSA biannually and those over age 80 visit annually.

• Finger tapping assessment and many basic neurological tests strongly predict mobility and therefore should be included in geriatric wellness exams. • EMG testing is likely an unnecessary expense, unless assessing for pathology (i.e. peripheral neuropathy). Though some aspects of nerve conduction predict physical performance, they have relatively weak significance and do not predict decline. • Subsequent research could analyze other neurological signs, such as irregularities in non-pathological reflexes, pronator drift, dysmetria, or disdiadochokinesia, to see if they predict physical performance or decline. • Additionally, since this study analyzed a wide range of neurological and performance variables, the future scope should be narrowed in order to match particular areas of neurological dysfunction with specific aspects of poor mobility.

Neurological Measures: • Electromyography (EMG)- nerve conduction velocity and amplitude • BLSA physical examination (conducted by nurses):

o Finger tapping assessment

o Tests for graphesthesia , cranial nerve abnormalities, Romberg sign, and pathological reflexes

Performance Measures: • Health ABC Physical Performance Battery:

o Repeat chair stands o Standing balances- up to 30 s each for semi- and full- tandem and single leg stands o Narrow gait speed - fastest of 3 trials over 6 m in a 20 cm wide path o Usual gait speed - faster of 2 trials over 6 m

• Rapid gait speed- faster of 2 trials over 6 m

Measures

Population Statistics

RESULTS

Men N= 411*

Women N= 407*

Mean Age 74.9 72.6

Percent Black Race 17.5 29.7

Mean Measured BMI 27.7 27.3

Percent Sedentary (report ≤ 30 minutes of physical activity per week)

37.7 44.7

Percent with Pathological Nerve Conduction

51.4 31.7

Percent that Show 1+ Neurological Sign(s)

51.1 41.8

*N ≈ 450 for the EMG data, N ≈ 590 longitudinal analysis

SAS Statistical Analysis • Cross-sectional analyses: general linear models (discrete predictors) or linear regression (continuous predictors). • Longitudinal analyses: logistic regression.

• Age associated changes to the neuromuscular system result in decreased muscular force, motor speed, coordination, and mobility. • There exists strong evidence that decline in neurological and physical realms are closely tied. • Decline in physical performance can cause inability to comfortably achieve everyday tasks and predict mortality.

HABCPPB (points)

R2= 0.417 p<0.001*

Rapid Gait (m/s)

R2= 0.410 p<0.001*

Usual Gait (m/s)

R2= 0.296 p<0.001*

0

5

10

15

20

25

30

35

40

45

Usual Gait Speed

Rapid Gait Speed

Physical Performance

Battery

Standing Balance Time

Pe

rce

nt

De

clin

ed

Number of Dominant Hand Finger Taps in 10 Seconds

Finger Tapping and Decline in Physical Performance

9-18

19-28

29-38

OR= 0.852 p< 0.001*

OR= 0.931 p= 0.041*

OR= 0.929 p= 0.029*

OR= 0.924 p= 0.021*

0

5

10

15

20

25

30

35

40

45

Usual Gait Speed

Rapid Gait Speed

Physical Performance

Battery

Standing Balance Time

Pe

rce

nt

De

clin

ed

Pathological Reflexes

Pathological Reflexes and Decline in Physical Performance

Present

Absent

OR= 0.411 p< 0.001*

OR= 0.664 p= 0.082

OR= 0.645 p= 0.059

OR= 0.737 p= 0.207

Cross-Sectional Longitudinal *β values are from minimally adjusted

model **∆µ= difference in

physical performance mean

between neurological groups

Performance Outcome

Not Significant

Minimally adjusted model, only

Minimally and fully adjusted models

Independent predictor

Neurological Predictor

HABC PPB

(points)

Chair Stands (#/s)

Balance Time

(s)

Narrow Gait

(m/s)

Usual Gait

(m/s)

Rapid Gait

(m/s)

Sensory NCV (m/s)

*β= 0.013

β= 0.002

β= 0.474

β= 0.009

β= 0.004

β= 0.004

Motor NCV (m/s)

β= 0.014

β= 0.002

β= 0.568

β= 0.007

β= 0.005

β= 0.011

Sensory NCA (mV)

β= 0.012

β= 0.003

β= 0.252

β= 0.009

β= 0.005

β= 0.006

Motor NCA (mV)

β= 0.057

β= 0.012

β= 1.374

β= 0.042

β= 0.021

β= 0.030

Finger Taps (#/10 s)

β= 0.034

β= 0.009

β= 0.627

β= 0.022

β= 0.012

β= 0.025

Graphesthesia (Able/Unable)

**∆µ= 0.218

∆µ= 0.042

∆µ= 8.046

∆µ= 0.125

∆µ= 0.051

∆µ= 0.105

Cranial Nerves (Norm/Abnorm)

∆µ= 0.178

∆µ= 0.014

∆µ= 7.647

∆µ= 0.140

∆µ= 0.042

∆µ= 0.056

Romberg Sign (Neg/Pos)

∆µ= 0.424

∆µ= 0.088

∆µ= 15.865

∆µ= 0.225

∆µ= 0.077

∆µ= 0.170

Path Reflexes (Abs/Pres)

∆µ= 0.130

∆µ= 0.028

∆µ= 4.763

∆µ= 0.068

∆µ= 0.039

∆µ= 0.059

Hypothesis

Note: Other neurological predictors did not have enough power to be analyzed or were not significant predictors of

decline in physical performance when using the fully adjusted model.

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Meaningful Decline (Longitudinal analyses):

• Usual gait speed decline ≥ 0.08 m/s/yr • Rapid gait speed decline ≥ 0.10 m/s/yr • HABCPPB score decline ≥ 0.14 points/yr • Standing balance time decline ≥ 6.00 s/yr