The measurement error structure of the ASA24 and ACT24 needs to be evaluated. The iDATA Study will compare objectively measured energy expenditure, protein, nutrients, and physical activity with the self-reported intakes of energy, protein, nutrients, and physical activity using the ASA24 and ACT24, as well as conventional self-report instruments for assessing diet and physical activity in a free-living population aged 50 to 74 years and residing in the Pittsburgh, Pennsylvania area. To date there has not been a comparable effort to understand the properties and measurement error structure of self-report physical activity instruments. The burgeoning epidemic of obesity highlights the need to explore this in both aspects of energy balance - dietary intake and energy expenditure through physical activity. Other studies have shown significant disagreement between typical, long-term memory-based self-reported activity and objective wearable motion detection devices. To address this, NCI has developed a new internet-based instrument, ACT24, which measures the participant's past 24-hour activities in order to improve the accuracy of self-reported physical activity.
Results from previous studies have indicated that multiple 24-hour dietary recalls over the course of one year provide more accurate information about usual dietary exposure and create less bias in estimated risk compared with the typical Food Frequency Questionnaires (FFQ) that asks participants to remember dietary information over the entire past year. An obstacle to the 24-hour recall method is that it is typically administered by interviewers, and is prohibitively expensive to use in large studies, especially multiple administrations. In response, NCI has developed a self-administered internet-based version, ASA24, which allows multiple recalls to be collected at very limited study expense and relatively low participant burden.
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