Background: Single-method assessment of physical activity (PA) has limitations. The utility and cross-validation of a composite PA score that includes reported and accelerometer-derived PA data has not been evaluated. Methods: Participants attending the Year 20 exam were randomly assigned to the derivation (two-thirds) or validation (one-third) data set. Principal components analysis was used to create a composite score reflecting Year 20 combined reported and accelerometer PA data. Generalized linear regression models were constructed to estimate the variability explained (R2) by each PA assessment strategy (self-report only, accelerometer only, composite score, or self-report plus accelerometer) with cardiovascular health indicators. This process was repeated in the validation set to determine cross-validation. Results: At Year 20, 3549 participants (45.2 [3.6] y, 56.7% female, and 53.5% black) attended the clinic exam and 2540 agreed to wear the accelerometer. Higher R2 values were obtained when combined assessment strategies were used; however, the approach yielding the highest R2 value varied by cardiovascular health outcome. Findings from the cross-validation also supported internal study validity. Conclusions: Findings support continued refinement of methodological approaches to combine data from multiple sources to create a more robust estimate that reflects the complexities of PA behavior.
Pettee Gabriel is with the Department of Epidemiology, Human Genetics & Environmental Sciences, School of Public Health, The University of Texas Health Science Center at Houston, Houston, TX; and the Department of Women's Health, Dell Medical School, The University of Texas at Austin, Austin, TX. Pérez is with the Department of Biostatistics and Data Sciences, University of Texas School of Public Health, Austin, TX. Jacobs is with the Division of Epidemiology & Community Health, University of Minnesota, Minneapolis, MN. Lee and Kohl are with the Department of Epidemiology, Human Genetics & Environmental Sciences, University of Texas School of Public Health, Austin, TX. Sternfeld is with the Division of Research, Kaiser Permanente, Oakland, CA.