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 (R 2) 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 R 2 values were obtained when combined assessment strategies were used; however, the approach yielding the highest R 2 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.
Kelley Pettee Gabriel, Adriana Pérez, David R. Jacobs Jr, Joowon Lee, Harold W. Kohl III and Barbara Sternfeld
Andrea Stewart, Barbara Sternfeld, Brittney S. Lange-Maia, Kelly R. Ylitalo, Alicia Colvin, Carrie A. Karvonen-Gutierrez, Sheila A. Dugan, Robin R. Green and Kelley Pettee Gabriel
Purpose: To examine racial/ethnic differences in participant-reported and device-based estimates of sedentary and physical activity behaviors and correlations between measurement methods in midlife and young-old women. Methods: Data are from 1,257 Study of Women’s Health Across the Nation participants, aged 60–72 who agreed to participate in an accelerometer protocol and had valid wear time (46% White, 26% Black, 12% Chinese, 10% Japanese, 6% Hispanic). Measures from the Kaiser Physical Activity Scale (KPAS) and ActiGraph wGT3X-BT were summarized overall and by race/ethnic groups. Partial Spearman rank order correlation coefficients between the KPAS and accelerometer were computed overall and by race/ethnic groups. Fisher’s z transformation-derived confidence intervals were calculated to evaluate differences in observed correlations in the various race/ethnic groups, compared to White women. Results: Participants spent an average of 7.5 ± 2.1 h·d−1 in sedentary behaviors, 4.5 ± 1.1 h·d−1 and 2.3 ± 0.8 h·d−1 in low or high light intensity physical activity, respectively, and 56 ± 35 min·d−1 in moderate-to-vigorous intensity physical activity. Time spent in each category differed by race/ethnic group. Overall, correlation coefficients comparing the KPAS domain-specific and total physical activity scores with accelerometry were low to moderate (range: 0.062–0.462), and few statistically significant differences in correlations were noted for race/ethnic groups, compared to White women. Conclusions: Study findings complement prior studies describing sedentary and physical activity behaviors using multi-methods in a diverse population of older women, and provide additional evidence on the convergent validity of the KPAS by race/ethnic groups.