Reliability of a Measure of Prediagnosis Physical Activity
Reliability of a Measure of Prediagnosis Physical Activity
Purpose: This study was conducted to examine the test-retest reliability of a measure of prediagnosis physical activity participation administered to colorectal cancer survivors recruited from a population-based state cancer registry.
Methods: A total of 112 participants completed two telephone interviews, 1 month apart, reporting usual weekly physical activity in the year before their cancer diagnosis. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were used to describe the test-retest reliability of the measure across the sample; the Bland-Altman approach was used to describe reliability at the individual level. The test-retest reliability for categorized total physical activity (active, insufficiently active, sedentary) was assessed using the kappa statistic.
Results: When the complete sample was considered, the ICC ranged from 0.40 (95% CI: 0.24, 0.55) for vigorous gardening to 0.77 (95% CI: 0.68, 0.84) for moderate physical activity. The SEM, however, were large, indicating high measurement error. The Bland-Altman plots indicated that the reproducibility of data decreases as the amount of physical activity reported each week increases. The kappa coefficient for the categorized data was 0.62 (95% CI: 0.48, 0.76).
Conclusion: Overall, the results indicated low levels of repeatability for this measure of historical physical activity. Categorizing participants as active, insufficiently active, or sedentary provides a higher level of test-retest reliability.
Evidence is accumulating that physical activity can play an important role in improving quality of life and reducing symptoms and treatment side-effects among cancer patients and survivors. Observational studies have shown that both current level of physical activity and change in physical activity from pre- to postdiagnosis are associated with reported quality of life. Further, these studies suggest that maintenance of, or an increase in, physical activity from prediagnosis to postdiagnosis is optimal for quality of life outcomes.
To determine change in physical activity from pre- to postdiagnosis, researchers employ self-report measures of past physical activity. Whereas a number of measures of recent physical activity are known to be valid and reliable, measures of historical physical activity have not been tested as extensively. Studies that have assessed recall of historical physical activity by following a cohort over time and comparing recall of past activity to self-reports collected in the past have found that vigorous activity is more reliably recalled than other activities. Self-reported historical physical activity has also been shown to be correlated with objective, physiological measures such as cardiorespiratory fitness and body mass index.
Only two published studies have assessed the test-retest reliability of historical physical activity measures. Cumming and Klineberg assessed the test-retest reliability of long-term recall of physical activity among 63 elderly participants, performing the interviews 1-3 months apart. Participants were asked to recall the type of physical activity (main sport and occupational activity level) they performed at ages 20 and 50, and to recall the number of times per week certain activities were undertaken. The test-retest reliability of these physical activity items was generally poor, with decreased reproducibility associated with increasing age (>65 yr) and with being male.
Friedenreich et al. assessed the test-retest reliability of a measure of lifetime pattern of physical activity, with 113 healthy middle-aged women who completed two interviews within a 6- to 8-wk period. Participants recalled activity at stages from childhood through to the year before the interview. The measure was found to have good test-retest reliability across different types of activity, across time periods, and across intensity levels. No clear pattern emerged of change in the correlations with length of recall periods; the test-retest reliability of activity recall in the preceding year was in some instances lower than for recall over 50 yr.
The published research assessing the test-retest reliability of historical measures of physical activity is very limited, and the reliability of self-reported past physical activity has not yet been reported for cancer survivors. We therefore examined the test-retest reliability of a measure of physical activity occurring during the 12 months before diagnosis, in a sample of colorectal cancer survivors recruited from a population-based state cancer registry.
Purpose: This study was conducted to examine the test-retest reliability of a measure of prediagnosis physical activity participation administered to colorectal cancer survivors recruited from a population-based state cancer registry.
Methods: A total of 112 participants completed two telephone interviews, 1 month apart, reporting usual weekly physical activity in the year before their cancer diagnosis. Intraclass correlation coefficients (ICC) and standard error of measurement (SEM) were used to describe the test-retest reliability of the measure across the sample; the Bland-Altman approach was used to describe reliability at the individual level. The test-retest reliability for categorized total physical activity (active, insufficiently active, sedentary) was assessed using the kappa statistic.
Results: When the complete sample was considered, the ICC ranged from 0.40 (95% CI: 0.24, 0.55) for vigorous gardening to 0.77 (95% CI: 0.68, 0.84) for moderate physical activity. The SEM, however, were large, indicating high measurement error. The Bland-Altman plots indicated that the reproducibility of data decreases as the amount of physical activity reported each week increases. The kappa coefficient for the categorized data was 0.62 (95% CI: 0.48, 0.76).
Conclusion: Overall, the results indicated low levels of repeatability for this measure of historical physical activity. Categorizing participants as active, insufficiently active, or sedentary provides a higher level of test-retest reliability.
Evidence is accumulating that physical activity can play an important role in improving quality of life and reducing symptoms and treatment side-effects among cancer patients and survivors. Observational studies have shown that both current level of physical activity and change in physical activity from pre- to postdiagnosis are associated with reported quality of life. Further, these studies suggest that maintenance of, or an increase in, physical activity from prediagnosis to postdiagnosis is optimal for quality of life outcomes.
To determine change in physical activity from pre- to postdiagnosis, researchers employ self-report measures of past physical activity. Whereas a number of measures of recent physical activity are known to be valid and reliable, measures of historical physical activity have not been tested as extensively. Studies that have assessed recall of historical physical activity by following a cohort over time and comparing recall of past activity to self-reports collected in the past have found that vigorous activity is more reliably recalled than other activities. Self-reported historical physical activity has also been shown to be correlated with objective, physiological measures such as cardiorespiratory fitness and body mass index.
Only two published studies have assessed the test-retest reliability of historical physical activity measures. Cumming and Klineberg assessed the test-retest reliability of long-term recall of physical activity among 63 elderly participants, performing the interviews 1-3 months apart. Participants were asked to recall the type of physical activity (main sport and occupational activity level) they performed at ages 20 and 50, and to recall the number of times per week certain activities were undertaken. The test-retest reliability of these physical activity items was generally poor, with decreased reproducibility associated with increasing age (>65 yr) and with being male.
Friedenreich et al. assessed the test-retest reliability of a measure of lifetime pattern of physical activity, with 113 healthy middle-aged women who completed two interviews within a 6- to 8-wk period. Participants recalled activity at stages from childhood through to the year before the interview. The measure was found to have good test-retest reliability across different types of activity, across time periods, and across intensity levels. No clear pattern emerged of change in the correlations with length of recall periods; the test-retest reliability of activity recall in the preceding year was in some instances lower than for recall over 50 yr.
The published research assessing the test-retest reliability of historical measures of physical activity is very limited, and the reliability of self-reported past physical activity has not yet been reported for cancer survivors. We therefore examined the test-retest reliability of a measure of physical activity occurring during the 12 months before diagnosis, in a sample of colorectal cancer survivors recruited from a population-based state cancer registry.