Self-reported Fatigue: Relationships with Physical Function and Oxygen Uptake in Leg Osteoarthritis and Type 2 Diabetes

Mobility Research Center (MRC)1; Department of Physical Medicine and Rehabilitation, University of Michigan2 ; Geriatrics Center and Division of Geriatric Medicine3 University of Michigan Hospitals;

VA Ann Arbor Health Care System Geriatric Research Education and Clinical Center (GRECC)4

Acknowledgments: National Institute on Aging; National Center for Medical Rehabilitation Research; American College of Rheumatology Research and Education

Foundation; VA Office of Research and Development (Rehab R&D and Medical Research Services)

Susan Murphy ScD, OTR1,2,4

Neil Alexander MD1,2,3,4

Presentation

Part I: Older women with leg osteoarthritisA. Daily pain and fatigue, in relation to

physical activityB. Behavioral intervention to reduce barriers

to PA and increase symptom controlPart II: Task-specific oxygen uptake and self-

reported fatigue in older adultsA. As predictors of mobility performanceB. In Type 2 diabetes mellitus

Symptoms and Physical Activity in Women with OA

• 60 women (40 with knee or hip OA, 20 controls)

• Mean age 64 + 8 years• 5 day home assessment

– Watch measured physical activity; recorded symptoms 6 times/day

– Pain/fatigue measured on scale of (0- none to 4-extremely severe)

– Fatigue defined as “tiredness or weariness”

Part I A: Clinical Research Questions

• How do pain and fatigue symptoms manifest in daily routines?

• How do pain and fatigue symptoms impact physical activity?

Pain in Women with OA and Controls (data depicted as means + SE)

0

0.5

1

1.5

2

2.5

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

All Timepoints over 5 days

Pain

0-4

controlOA

Day 1 Day 2 Day 3 Day 4 Day 5

Fatigue in Women with OA and Controls (data depicted as means + SE)

0

0.5

1

1.5

2

2.5

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29

All Timepoints over 5 days

Fatig

ue 0

-4

controlOA

Day 1 Day 2 Day 3 Day 4 Day 5

Momentary Within-Day Symptoms by WOMAC Physical Disability

0

0.5

1

1.5

2

2.5

Low WOMAC Physical Disability High WOMAC Physical Disability

Sym

ptom

Sev

erity

PainFatigue

Dependent Variable: Physical Activityβ

estimateStandard

Error P valueFatigue -30.08 6.21 <.0001

Pain -16.86 8.36 .04

Age -2.43 1.79 .18

Geriatric Depression Scale -7.52 5.40 .17

Daily Medication Use -2.07 14.50 .89

Timed Up and Go Test -14.30 6.00 .02

Summary and Conclusions • For women with mildly painful OA, momentary

fatigue may increase more disproportionately through the day than pain, particularly in those with higher disability (more pain)

• In addition to pain, increased momentary fatigue is associated with decreased physical activity

• Interventions to increase physical activity and manage symptoms in leg osteoarthritis may need a better emphasis on fatigue

Murphy SL et al. Arthritis Rheum 2008

Part 1 B: Behavioral Intervention• Current exercise programs for OA limited in their

link to activity or environmental context, nor are they designed to reduce individual barriers to PA and improve symptom control

• Hypothesis: Compared to those randomized to group exercise

and health education, can group exercise plus activity strategy training (AST, an OT approach) more effectively improve pain, fatigue, and physical activity?

• Design:– 1 month intervention with 2 and 4 month boosters– 6 month follow-up

Baseline Characteristics

EX + ED(n=26)

EX + AST (n=28)

P value

Age (years) 74.8 (7.3) 75.8 (7.1) .65

No. of women (%) 22 (85) 26 (93) .33

BMI (kg/m2) 30.0 (4.8) 30.1 (6.5) .98

No. of chronic conditions 1 (1.2) 1.5 (1.4) .17

No. of painful joints 4.6 (2.1) 4.4 (2.1) .79

(Murphy SL et al, Arthritis Rheum, in press)

EX+ED EX+AST

Pain and Fatigue Symptoms in OA PatientsPre and Post Intervention

0

2

4

6

8

PRE POST

fatigue

pain

Fatigue - Brief Fatigue Inventory, severity subscale; Pain – WOMAC pain subscale

Pain (time) p<0.005

Fatigue (time x group) p<0.05

Trend for fatigue to decrease in AST and increase in ED

Daily Peak Activity

600

640

680

720

760

Pre-Intervention Post-Intervention

Activ

ity C

ount

s

EX+ED EX+AST

Activity counts – collected via wrist-worn accelerometry (Actiwatch, MiniMitter-Respironics)

Trend for peak activity to increase in AST and decrease in ED

(time x group) p<0.05

Summary and Conclusions

• Compared to controls. participants in a group exercise plus activity strategy training designed to reduce individual barriers to PA and improve symptom control had:– Reductions in pain– Reductions in fatigue– Improvements in peak physical activity

Part II: Task-specific oxygen uptake and self-reported fatigue in older adults

• Global question: How does aerobic function relate to: – mobility performance?– symptoms of exertion and fatigue?

• A: Analysis of peak V02 versus submaximal oxygen kinetics in predicting mobility performance.

• B: In Type 2 diabetics, analysis of VO2 during peak GXT, submax, and six minute walk (6MW) in predicting perceived exertion (RPE) and fatigue

Background and Significance

• Age- and disease-associated declines in aerobic capacity (VO2 Max) contribute to functional disability in older adults.

• Standard VO2 measures may be limited– Max VO2 (e.g. max treadmill) is difficult to

achieve in older adults– Peak VO2 is frequently reported

Background and Significance (2)

• The aerobic demands of many ADL’s are submaximal

• Measures of submaximal (vs maximal or peak) aerobic fitness might:– Be easier and safer to perform, especially

for frail older adults– Better predict functional ability

Oxygen Kinetics in Healthy and Mobility Impaired Older Women

0 180 360 540 720 900

Time (seconds)

Healthy Woman

RestWalking (1.0 mph) Recovery

(63.7 mL)

(944.1 mL)

0

200

400

600

800

1000

Oxy

gen

Upt

ake

(mL/

min

)

O2 Deficit

O2 Debt

0 180 360 540 720 900

Time (seconds)

Mobility Impaired Woman

RestWalking (1.0 mph) Recovery

(873.0 mL)

(1734.4 mL)

0

200

400

600

800

1000

Oxy

gen

Upt

ake

(mL/

min

)

O2 Deficit

O2 Debt

Mean (SEM) Comparisons: Aerobic Unimpaired (n=21) vs Impaired (n=20)

Unimpaired Impaired

Age (yrs) 76 (1) 82 (1)*

Peak VO2 (ml/kg/min) 24 (1) 14 (1)*

TCdeficit (s) 23 (3) 58 (9)*

TCepoc (s) 40 (7) 57 (7)

Get up + Go (s) 12 (1) 20 (2)*

6-min-walk (m) 415 (17) 286 (27)*

*p<0.05

(Alexander, J Gerontol, 2003)

Tcdeficit => Initial oxygen deficitTcepoc => Excess post-exercise oxygen

consumption

Peak VO2 and Oxygen Kinetics versus Functional Performance: Unimpaired Old

Task Peak VO2 tcdeficit tcEPOC Peak VO2 0.62** 0.29

GUG 0.48* 0.58* 0.06

GUG x 3 0.55* 0.60** 0.13

Bag Carry 0.29 0.22 0.59**

Six Min Wk 0.45* 0.31 0.15

** p<0.01; * p<0.05 (Alexander, J Gerontol, 2003)

Peak VO2 and Oxygen Kinetics versus Functional Performance: Impaired Old

Task Peak VO2 tcdeficit tcEPOC Peak VO2 0.11 0.49*

GUG 0.21 0.10 0.42

GUG x 3 0.41 0.02 0.33

Bag Carry 0.35 0.07 0.53*

Six Min Wk 0.62** 0.18 0.64**

** p<0.01; * p<0.05 (Alexander, J Gerontol, 2003)

Summary and Conclusions• Older adults with aerobic impairment have:

– Slowed submaximal oxygen kinetics– Poor functional mobility performance

• Measures of submaximal oxygen kinetics correlate as highly with functional mobility performance as Peak VO2 measures, particularly for impaired old during post-exercise recovery.

• Submaximal VO2 kinetics may be more useful than Peak VO2 in estimating the contribution of aerobic function to mobility impairment.

Type 2 Diabetics[Enrolled in RCT ex program, age >60, n=56 [27 female]

Mean (SD) Range

Age (years) 70.4 (5.7) 60-83

BMI 33.6 (5.9) 24-50

EPESE total 1.0 (1.2) 0-6.0

BFI (global) 2.0 (1.8) 0-7.3

BFI (severity) 2.9 (2.2) 0-8.3

6MW dist (feet) 1264.5 (229.6) 660-1960

Comf Gait Sp (m/s) 1.2 (0.2) 0.8-1.5

Oxygen Uptake (VO2) Measurements

Three tasks:Graduated treadmill

(traditional peak)Submaximal treadmill

(1 MPH)Six minute walk

Self Report Measurements

During exercise task:• Rated Perceived Exertion (RPE): How hard

you worked– Range 6-20; 11=fairly light; 13=somewhat

hard; 15=hard; 17=very hard• Fatigue: How much fatigue you had

– 0=No fatigue; 10=Fatigue as bad as could be

0

5

10

15

20

25

Peak VO2 During TaskSubmax6MWGXT

Mean(SD)

OxygenUptake

(ml/kg/min)

*

*

*

0

5

10

15

20

Post-Task Rate of Perceived Exertion (RPE) Submax6MWGXT

Mean(SD)RPE

Score

0

5

10

15

20

25

Peak VO2 During TaskSubmax6MWGXT

Mean(SD)

OxygenUptake

(ml/kg/min)

*

*

*

0

1

2

3

4

5

6

7

8

Fatigue Post-TaskSubmax6MWGXT

Mean(SD)

FatigueScore

*

*

*

Self-reported task-specific fatigue is not related to general fatigue

Fatigue during task GXT Submax 6MW BFI global 0.12 0.18 -0.04 BFI severity 0.12 0.07 -0.11 Submax fatigue 0.52* 0.50* 6MW fatigue 0.39* 0.50* GXT fatigue 0.52* 0.39*

Non-GXT task-related fatigue may better relate to usual mobility function

Fatigue during task GXT Submax 6MW BFI global 0.12 0.18 -0.04 BFI severity 0.12 0.07 -0.11 EPESE 0.14 0.32* 0.16 TUG 0.28* 0.31* 0.16 Comf Gait Sp -0.25 -0.32* -0.22 6MW dist -0.14 -0.47* -0.32*

Task specific self-reported fatigue relates more to VO2 kinetics than peak VO2

Fatigue during task GXT Submax 6MW Peak GXT VO2 -0.12 Peak Submax VO2 -0.04 Peak 6MW VO2 -0.05 Submax Tc deficit 0.15 Submax Tc EPOC 0.34* 6MW Tc deficit 0.33* 6MW EPOC 0.39*

Summary and ConclusionsIn this group of relatively functional older adult

Type 2 diabetics:• Peak VO2 and post-task fatigue increase with

task demand• Self-reported task-specific fatigue is not

related to general fatigue• Non-GXT task-related fatigue may better

relate to usual mobility function• Task specific self-reported fatigue relates

more to VO2 kinetics than peak VO2

Discussion• Measures acquired during submaximal exercise

tests, including 6MW, as opposed to peak GXT, are better indicators of physical function, and likely fatigue.

• Future studies should consider:– Whether these relationships hold true for

other models of disability and fatigue (such as in non-cardiac disease, high baseline fatigue)

– What the underlying physiological link is between subjective fatigue and objective measures of oxygen utilization