Fatigue and Fatigability

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Fatigue and Fatigability
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Fatigue and Fatigability

• Concept of fatigability
• How it could be used in assessment and in
  evaluating responses to interventions

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(No Transcript)
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Individuals Fatigue-Activity Relationship
(Fatigability Function) A Phenotype of
Interest
Fatigue Level
Activity Level (physical, mental, social) effort
x time.
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Fatigability Can Limit Activity
.
A
Fatigue Level
Tolerable Fatigue Ceiling
Activity Limit
Activity Level (physical, mental, social) effort
x time.
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Fatigue and Physical Function Scores by AgeWHI
Women ages 50-79
RAND-36 Energy/Fatigue subscale How much of the
time during the past 4 weeks did you feel full
of pep? have a lot of energy? feel worn out?
feel tired? RAND-36 Physical Function
subscale Does your health now limit you in
these activities? If so, how much?

• Vigorous activities, e.g., running, lifting,
  heavy objects, strenuous sports
• Moderate activities, e.g., moving a table,
  pushing a vacuum cleaner, bowling, golf
• Lifting or carrying groceries
• Climbing several flights of stairs
• Climbing one flight of stairs
• Bending, kneeling, or stooping

• Walking more than a mile
• Walking several blocks
• Walking one block
• Bathing or dressing myself

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Increased Fatigability Can Cause Disability
.
.
B
A
Fatigue Level
Tolerable Fatigue Ceiling
Old Activity Limit
New Activity Limit
Activity Level (physical, mental, social) effort
x time.
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A goal for interventions to reduce fatigability

• To be able to do all that one would like to do
  over the course of the day, without feeling more
  fatigued than one is willing to tolerate

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A goal for interventions to reduce fatigability

• To be able to do all that one would like to do
  over the course of the day, without feeling more
  fatigued than one is willing to tolerate.

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A goal for interventions to reduce fatigability

• To be able to do all that one would like to do
  over the course of the day, without feeling more
  fatigued than one is willing to tolerate

How much activity you are willing to tolerate in
a day is related to two dimensions of
fatigability

• Capacity How much you can do before you get too
  fatigued?
• Rate How fast can you do it without getting too
  fatigued?
• (Differing physiologic factors may affect
  capacity versus rate.)

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Diurnal Patterns of Tiredness in Employed
Women Accumulation of Fatigue Over the Day in
Older Women
4.5
4.0
Under 30
3.5
Tiredness
3.0
2.5
30-49
2.0
50
1.5
1.0
21
18
15
12
9
6
22
20
19
17
16
14
13
11
10
8
7
Hour of Day
Kahneman, Krueger, Schkade, Schwarz, Stone,
Science, 2004
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Measuring Fatigue and Activity Over the Day

• ecological momentary assessment (EMA)
• experience sampling method (ESM)
• day reconstruction method (DRM)
• References
• Shiffman S, Stone A, Hufford M. Ecological
  momentary assessment. Annu Rev Clin Psychol
  20084 1-32
• Smith DM, Brown SL, Ubel PA. Mispredictions and
  misrecollections challenges for subjective
  outcome measurement. Disabil Rehabil 200830(6)
  418-24.
• Murphy SL, Smith DM, Clauw DJ, Alexander NB. The
  impact of momentary pain and fatigue on physical
  acitivity in women with osteoarthritis. Arthritis
  and Rheumatism 2008 59(6) 849-856

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A goal for interventions to reduce fatigability

• To be able to do all that one would like to do
  over the course of the day, without feeling more
  fatigued than one is willing to tolerate

How much activity you are willing to tolerate in
a day is related to two dimensions of
fatigability

• Capacity How much you can do before you get too
  fatigued?
• Rate How fast can you do it without getting too
  fatigued?

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Activity-rate-limiting fatigability can limit
total daily activity and functional
status
12 10 8 6 4 2
Number of activities done (ADLs, IADLS, etc.)
B
6 9 12 15 18 21
Hour
N.B. At any time during the day, individual As
fatigue level equals individual Bs fatigue level.
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A goal for interventions to reduce fatigability

• To be able to do all that one would like to do
  over the course of the day, without feeling more
  fatigued than one is willing to tolerate

• Some levels of fatigue are highly tolerable
  (e.g., during exercise).
• Though scales of fatigue severity are valuable
  for several purposes, dichotomizing between
  tolerable/intolerable can be useful, particularly
  for relating fatigue to activity and function.

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Different daily activity profiles for persons
acting at tolerable fatigue level
12 10 8 6 4 2
Number of activities done (ADLs, IADLS, etc.)
C
B
6 9 12 15 18 21
Hour
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Capacities for Daily Activities with Tolerable
Fatigue Assessment

• Identify the daily activities that an individual
  needs to do (e.g., ADLs), plus additional ones
  that s/he wants to be able to do in the course of
  a day (exercise, other activities).

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Capacities for Daily Activities with Tolerable
Fatigue Assessment

• Identify the daily activities that an individual
  needs to do (e.g., ADLs), plus additional ones
  that s/he wants to be able to do in the course of
  a day (exercise, other activities.
• Assess how many of them the s/he can do in the
  course of a day without feeling intolerably
  fatigued.

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Capacities for Daily Activities with Tolerable
Fatigue Assessment

• Identify the daily activities that an individual
  needs to do (e.g., ADLs), plus additional ones
  that s/he wants to be able to do in the course of
  a day (exercise, other activities).
• Assess how many of them the s/he can do in the
  course of a day without feeling intolerably
  fatigued.
• Assess times and activities during which s/he
  experiences fatigue severe enough to stop or slow
  down.

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Capacities for Daily Activities with Tolerable
Fatigue Assessment

• Identify the daily activities that an individual
  needs to do (e.g., ADLs), plus additional ones
  that s/he wants to be able to do in the course of
  a day (exercise, other activities.
• Assess how many of them the s/he can do in the
  course of a day without feeling intolerably
  fatigued.
• Assess times and activities during which s/he
  experiences fatigue severe enough to stop or slow
  down.
• Assessment could be based on self-reports (e.g.,
  ecological momentary assessment), on observation,
  or by simulation methods (e.g., Easy Street)

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Capacities for Daily Activities with Tolerable
Fatigue Assessment

• Identify the daily activities that an individual
  needs to do (e.g., ADLs), plus additional ones
  that s/he wants to be able to do in the course of
  a day (exercise, other activities).
• Assess how many of them the s/he can do in the
  course of a day without feeling intolerably
  fatigued.
• Assess times and activities during which s/he
  experiences fatigue severe enough to stop or slow
  down.
• Assessment could be based on self-reports (e.g.,
  ecological momentary assessment), observation ,
  or by simulation methods (e.g., Easy Street)
• Assessment instrument could generate a simple
  score that could be used to assess responses to
  interventions to reduce fatigability (relevant
  for drug indications, health care coverage
  policies).

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Capacities for Daily Activities with Tolerable
Fatigue Assessment

• Identify the daily activities that an individual
  needs to do (e.g., ADLs), plus additional ones
  that s/he wants to be able to do in the course of
  a day (exercise, other activities.
• Assess how many of them the s/he can do in the
  course of a day without feeling intolerably
  fatigued.
• Assess times and activities during which s/he
  experiences fatigue severe enough to stop or slow
  down.
• Assessment could be based on self-reports (e.g.,
  ecological momentary assessment), observation ,
  or by simulation methods (e.g., Easy Street)
• Assessment instrument could generate a simple
  score that could be used to assess responses to
  interventions to reduce fatigability (relevant
  for drug indications, health care coverage
  policies).
• Does such an assessment instrument exist?

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Capacities for Daily Activities with Tolerable
Fatigue Differences from Disability Measures

• Standard disability measures tell you if someone
  can or cant do a a single task (e.g., walk a
  quarter-mile) with or without difficulty or
  assistance.

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Capacities for Daily Activities with Tolerable
Fatigue Differences from Disability Measures

• Standard disability measures tell you if someone
  can or cant do a a single task (e.g., walk a
  quarter-mile) with or without difficulty or
  assistance.
• They dont tell you how much this ability is
  affected by the burden of other requirements for
  independent living, i.e.,
• Even if you can walk a quarter-mile, are you too
  fatigued to do it after dressing, cleaning, and
  shopping?
• Even if you arent too fatigued after dressing,
  cleaning, and shopping, do you do them so slowly
  in order to avoid fatigue so that you dont have
  time to walk a quarter-mile after these
  activities?

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Capacities for Daily Activities with Tolerable
Fatigue Differences from Disability Measures

• Standard disability measures tell you if someone
  can or cant do a a single task (e.g., walk a
  quarter-mile) with or without difficulty or
  assistance.
• They dont tell you how much this ability is
  affected by the burden of other requirements for
  independent living, i.e.,
• Even if you can walk a quarter-mile, are you too
  fatigued to do it after dressing, cleaning, and
  shopping?
• Even if you arent too fatigued after dressing,
  cleaning, and shopping, do you do them so slowly
  in order to avoid fatigue so that you dont have
  time to walk a quarter-mile after these
  activities?
• Concept of capacities for daily activities with
  tolerable fatigue incorporates considerations of
  fatigability and speed in relation to disability.
  It may be a particularly meaningful outcome to
  many persons. (Have a good day.)