Estimating the effect of multiple imputation on incomplete longitudinal data with application to a randomized clinical study

Between- and within-person associations of mobile gaming time and total screen time with sleep problems in young adults: Daily assessment study

OBJECTIVES

To explore associations of screen time (total, mobile gaming) with sleep problems in Chinese young adults.

METHODS

This was a 4-week daily morning (completion rate = 82.1%, 909/1107) and evening (completion rate = 92.4%, 1061/1148) assessment study in 41 university students (22 female, mean age = 22.3 [SD 4.2] years). Short sleep duration < 7 h, difficulty initiating sleep, difficulty maintaining sleep, early morning awakening, and any of these three insomnia symptoms were self-reported in the morning. Mobile gaming time was self-reported in the evening, whilst total screen time was objectively tracked. Bayesian multilevel mixed-effects modeling disaggregated between- and within-person associations.

RESULTS

Between person, longer mobile gaming time predicted short sleep duration (adjusted odds ratio [AOR] = 1.90, 95% CI 1.39, 2.69), any insomnia symptoms (AOR = 1.59, 95% CI 1.20, 2.11), difficulty initiating sleep (AOR = 3.05, 95% CI 1.51, 6.24), and difficulty maintaining sleep (AOR = 2.19, 95% CI 1.18, 3.74). Short sleep duration (adjusted b = 0.99, 95% CI 0.05, 1.95), any insomnia symptoms (adjusted b = 1.19, 95% CI 0.24, 1.94), and difficulty initiating sleep (adjusted b = 1.72, 95% CI 0.11, 3.19) reversely increased mobile gaming time. Within person, any insomnia symptoms (adjusted b = 0.17, 95% CI 0.04, 0.31) and early morning awakening (adjusted b = 0.28, 95% CI 0.08, 0.48) increased next-day mobile gaming time. Total screen time was not associated with sleep problems both between and within person.

CONCLUSIONS

Bidirectional between-person associations of mobile gaming time with short sleep duration and insomnia symptoms informed multiple-health-behavior-change interventions. Unidirectional within-person associations of insomnia symptoms with next-day mobile gaming time informed just-in-time adaptive interventions addressing daily variations in insomnia symptoms. [250/250 word limits].

Protocol to assess the efficacy of carnosine supplementation in mitigating the adverse cardiovascular responses to particulate matter (PM) exposure: the Nucleophilic Defense Against PM Toxicity (NEAT) trial

INTRODUCTION

Exposure to airborne particulate matter (PM) is associated with cardiovascular disease. These outcomes are believed to originate from pulmonary oxidative stress and the systemic delivery of oxidised biomolecules (eg, aldehydes) generated in the lungs. Carnosine is an endogenous di-peptide (β-alanine-L-histidine) which promotes physiological homeostasis in part by conjugating to and neutralising toxic aldehydes. We hypothesise that an increase of endogenous carnosine by dietary supplementation would mitigate the adverse cardiovascular outcomes associated with PM exposure in humans.

METHODS AND ANALYSIS

To test this, we designed the Nucleophilic Defense Against PM Toxicity trial. This trial will enroll 240 participants over 2 years and determine if carnosine supplementation mitigates the adverse effects of PM inhalation. The participants will have low levels of endogenous carnosine to facilitate identification of supplementation-specific outcomes. At enrollment, we will measure several indices of inflammation, preclinical cardiovascular disease and physical function. Participants will be randomly allocated to carnosine or placebo groups and instructed to take their oral supplement for 12 weeks with two return clinical visits and repeated assessments during times of peak PM exposure (June-September) in Louisville, Kentucky, USA. Statistical modelling approaches will be used to assess the efficacy of carnosine supplementation in mitigating adverse outcomes.

ETHICS AND DISSEMINATION

This study protocol has been approved by the Institutional Review Board at the University of Louisville. Results from this study will be disseminated at scientific conferences and in peer-reviewed publications.Trial registration: NCT03314987; Pre-results.