Papers and abstracts

While right-censored time-to-event outcomes have been studied for decades, handling time-to-event covariates, also known as right-censored covariates, is now of growing interest. So far, the literature has treated right-censored covariates as distinct from missing covariates, overlooking the potential applicability of estimators to both scenarios. We bridge this gap by establishing connections between right-censored and missing covariates under various assumptions about censoring and missingness, allowing us to identify parallels and differences to determine when estimators can be used in both contexts. These connections reveal adaptations to five estimators for right-censored covariates in the unexplored area of informative covariate right-censoring and to formulate a new estimator for this setting, where the event time depends on the censoring time. We establish the asymptotic properties of the six estimators, evaluate their robustness under incorrect distributional assumptions, and establish their comparative efficiency. We conducted a simulation study to confirm our theoretical results, and then applied all estimators to a Huntington disease observational study to analyze cognitive impairments as a function of time to clinical diagnosis.

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 3.8h and moderate-to-vigorous physical activity was over-reported by 1.9h.

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.

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.

The lack of proper waste management behaviour creates environmental debasement and induces health risks. This study employs primary survey data collected in 2016 to investigate the association between health risks and improper waste management behaviour by households in three locations of Rupandehi District, Nepal. The health risk is measured by a series of water-related symptoms such as Diarrhea, Jaundice, Typhoid Fever, Worms, and Cholera. This paper’s novel contribution is that we identify the spatial nature of the prevalence of waterborne diseases and related factors such as solid waste management behaviour, hygiene infrastructure and personal cleanliness, and socio-economic status of the households. We use a spatial autoregressive model under the negative binomial family, and the result indicates a significant spatial autocorrelation of waterborne diseases. Moreover, we find the significant effect of improper waste management practices on waterborne diseases. The result is consistent even after various robustness and falsification tests. The findings from this study indicate the acute need to raise awareness concerning the malicious effect of improper waste management and the urge to provide wider access to waste management services.