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Validity and Reproducibility of Physical Activity
Questionnaires
Lisa Chasan-Taber, Sc.D. Patty S. Freedson, Ph.D.
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Research Interests
Chasan-Taber• Physical activity and
pregnancy– Effect on maternal/fetal
disorders– Development &
validation of measurement tools
• Reproductive & perinatal epidemiology
• Women's health
Freedson• Children's responses to
exercise• Exercise and women's
health• Determinants of
performance and fitness • Development and
validation of objective techniques to assess habitual physical activity
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Learning Objectives
1. To understand the need for evaluation of physical activity questionnaires
2. To understand the role of subjective and objective measures of physical activity in validity/reproducibility studies.
3. To understand approaches for analyzing validity/reproducibility studies.
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Performance Objectives
• Students should be able to design a study to assess the validity & reproducibility of a physical activity questionnaire.
• Be able to interpret the findings from a validity/reproducibility study.
• Be able to present findings from a reproducibility/validity study.
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Overview
1. Need for Evaluation of Physical Activity Questionnaires
2. Reproducibility Studies: Design, Analysis, & Presentation
3. Validity Studies: Design, Analysis, & Presentation
4. Future Directions
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Associations Between Physical Activity and
Disease
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Sedentary Occasional Conditioning Exercisers Exercisers
RR
Kujala, UM et al., JAMA 279:440-444, 1998
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Why are Questionnaires used to Measure Physical Activity in Epidemiologic Studies?
• Advantages– Practical for large sample sizes– Non-reactive– Tailored to specific populations and
time periods
• Disadvantages– Precision
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The Need for Validation of Physical Activity Questionnaires• Physical activity is a complex behavior
difficult to measure accurately– Based upon self-report – Includes unstructured activities
• Individuals rarely make clear changes in their activity at identifiable points in time.
• Activity intensity may vary from person to person
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Definition of Terms: Reproducibility
The consistency of questionnaire measurements •on more than one administration, •to the same people, •at different times.
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Definition of Terms: Validity
The degree to which the questionnaire actually measures the aspect of physical activity that it was designed to measure.• Type • Frequency• Duration• Intensity
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When to Perform Reproducibility/Validity Studies?
1. For new questionnaires.2. When a questionnaire is modified.3. When questionnaires will be used
in a different population according to:
– Age– Gender– Culture– Physical activity profile
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Design of Reproducibility Studies
1 s t M ea su rem en t 2 n d M ea su rem en t
Specify time interval
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Analysis of Reproducibility Studies
ICC
Total Activity 0.81
By Intensity
Light -Intensity Activity 0.64
Moderate -Intensity Activity 0.78
Vigorous -Intensity Activity
0.85
By Type
Occupational Activity
Recreational Activity 0.78
Household Activity 0.73
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Interpretation of Results from Reproducibility Studies
High reliability
High validity
High reliability
Low validity
Figure 1. Figure 2.
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Validity Studies: Choice of a Comparison Measure
• Use superior method as a comparison.
• No gold standard exists. • Use a method with different
sources of error.
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Comparison Measures• Subjective
– Physical activity logs (PALs)– 24 hour recall– 7 day recall– Previous month recall– Previous year recall
• Objective– Accelerometers– Heart rate monitoring– Doubly labeled water– Direct observation
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Subjective Comparison Measures- Physical Activity Logs (PALs)
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Advantages and Disadvantages of PALs as Comparison Measures
• Advantages– Open-ended– Alleviate memory difficulties
• Disadvantages– Subject cooperation and motivation– May alter normal activity– Share error of self report
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Computation of Summary Estimates from Subjective Measures
Frequency
1 times/day
Duration
2 hours/day
Intensity
5 METs
Total Energy Expenditure
30 MET-hrs/day
X X
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Objective Comparison Measures - Accelerometers
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Example Accelerometer Data
0
1000
2000
3000
4000
5000
6000
7000
8000
0 500 1000 1500 2000 2500 3000 3500 4000 4500 5000
Time (min)
# o
f C
ou
nts
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METS
Accelerometer Counts
<3METS
3-6METS
6-9METS
>9 METS
Computation of Summary Estimates from Accelerometer
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Example of Summary Estimates from Accelerometer
Day Min Min Total X Counts/ Mod Vig Counts Min
1 52 130 1247890 1122
2 16 141 1181263 1238
3 14 138 1135351 1169
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Design of Validity Studies
Questionnaire1st Admin.
Questionnaire2nd Admin.
ComparisonmeasureWinter
ComparisonmeasureSpring
ComparisonmeasureSummer
Comparisonmeasure
Fall
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Design of a Validation Study (Continued)
• The number of administrations of the comparison method should be based upon– Questionnaire time frame– Variation in physical activity– Subject burden
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Data Analysis & Presentation
Pearson Correlation Coefficients
Total Activity 0.50
By Intensity
Light 0.45
Moderate
0.55
Vigorous 0.70
By Type
Occupational 0.47
Recreational 0.60
Household 0.58
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Interpretation of Results from Validity Studies
• High validity may reflect correlated error– If both omit a source of activity– If both include questions that are
misinterpreted– If both rely upon self-report
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Summary• Evaluation of physical activity
questionnaires is critical• Goal is to assess typical or usual activity • A variety of comparison methods are
available• Study design should be tailored to the
specific population• Interpretation of results should be informed
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Future Directions• How much physical activity (dose) is needed
for health (response)? – Intensity– Duration– Frequency
• Improvements and standardization of methods to assess and validate physical activity.
• How sensitive are self-report and objective measures in detecting change consequent to physical activity interventions?