Concurrent validity of the Global Physical Activity Questionnaire to accelerometry in Hispanic/Latino adults: The Hispanic Community Health Study/Study of Latinos (HCHS/SOL).

OBJECTIVES: The validity of the Global Physical Activity Questionnaire has not been thoroughly evaluated among Hispanics/Latinos. In this cross-sectional study, we assessed the concurrent validity and correlates of discordance of the Global Physical Activity Questionnaire by comparing it to accelerometry in estimating sedentary behavior, moderate-to-vigorous physical activity, and meeting United States physical activity guidelines by sociodemographic, behavioral, and health characteristics. DESIGN: The Hispanic Community Health Study/Study of Latinos is a 4-site cohort study of United States adults aged 18-74 years enrolled from 2008 to 2011. METHODS: Participants (n = 11,873) completed the Global Physical Activity Questionnaire and wore an accelerometer for 1 week. Lin's concordance and Pearson correlations assessed concurrent validity between self-reported and accelerometry-assessed measures of sedentary behavior and moderate-to-vigorous physical activity. Kappa coefficients assessed agreement of meeting physical activity guidelines. Linear and logistic regression models identified correlates of discordance. RESULTS: The overall Lin's concordance and Pearson correlations between the Global Physical Activity Questionnaire and accelerometry estimates were 0.10 (95 % confidence interval 0.09, 0.12) and 0.24 (0.21, 0.27) for sedentary behavior, and 0.04 (0.03, 0.05) and 0.18 (0.15, 0.22) for moderate-to-vigorous physical activity, respectively. Agreement was poor for meeting the physical activity guideline classifications (Kappa coefficients: 0.12 to 0.26). Over a 16-hour day, sedentary behavior was under-reported by 3.8 h and moderate-to-vigorous physical activity was over-reported by 1.9 h. CONCLUSIONS: The concurrent validity of the Global Physical Activity Questionnaire in measuring moderate-to-vigorous physical activity and sedentary behavior when compared to accelerometry was poor among Hispanic/Latino adults.

Making Sense of Censored Covariates: Statistical Methods for Studies of Huntington's Disease.

The landscape of survival analysis is constantly being revolutionized to answer biomedical challenges, most recently the statistical challenge of censored covariates rather than outcomes. There are many promising strategies to tackle censored covariates, including weighting, imputation, maximum likelihood, and Bayesian methods. Still, this is a relatively fresh area of research, different from the areas of censored outcomes (i.e., survival analysis) or missing covariates. In this review, we discuss the unique statistical challenges encountered when handling censored covariates and provide an in-depth review of existing methods designed to address those challenges. We emphasize each method's relative strengths and weaknesses, providing recommendations to help investigators pinpoint the best approach to handling censored covariates in their data.