validity and reproducibility of physical activity questionnaires
DESCRIPTION
Validity and Reproducibility of Physical Activity Questionnaires. Lisa Chasan-Taber , Sc.D. Patty S. Freedson , Ph.D. Chasan-Taber Physical activity and pregnancy Effect on maternal/fetal disorders Development & validation of measurement tools Reproductive & perinatal epidemiology - PowerPoint PPT PresentationTRANSCRIPT
Validity and Reproducibility of Physical Activity
Questionnaires
Lisa Chasan-Taber, Sc.D. Patty S. Freedson, Ph.D.
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
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.
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.
Overview
1. Need for Evaluation of Physical Activity Questionnaires
2. Reproducibility Studies: Design, Analysis, & Presentation
3. Validity Studies: Design, Analysis, & Presentation
4. Future Directions
Associations Between Physical Activity and
Disease
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
Sedentary Occasional Conditioning Exercisers Exercisers
RR
Kujala, UM et al., JAMA 279:440-444, 1998
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
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
Definition of Terms: Reproducibility
The consistency of questionnaire measurements •on more than one administration, •to the same people, •at different times.
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
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
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
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
Interpretation of Results from Reproducibility Studies
High reliability
High validity
High reliability
Low validity
Figure 1. Figure 2.
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.
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
Subjective Comparison Measures- Physical Activity Logs (PALs)
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
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
Objective Comparison Measures - Accelerometers
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
METS
Accelerometer Counts
<3METS
3-6METS
6-9METS
>9 METS
Computation of Summary Estimates from Accelerometer
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
Design of Validity Studies
Questionnaire1st Admin.
Questionnaire2nd Admin.
ComparisonmeasureWinter
ComparisonmeasureSpring
ComparisonmeasureSummer
Comparisonmeasure
Fall
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
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
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
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
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?