CARDIA sleep ancillary study: study design and methods

Sleep and circadian disturbances are common and are experienced more often by Black compared to White individuals. We conducted an observational study of sleep that was ancillary to an ongoing cohort study, Coronary Artery Disease in Young Adults (CARDIA). The goal of the ancillary study will be to examine potential determinants of sleep/circadian disparities between Black and White adults in future analyses. Herein we describe the study design and methodology. Our ancillary study coincided with the Year 35 examination of the CARDIA study and was conducted in two phases (due to the SARS-COV-2 pandemic). Phase 1 involved only questionnaires to assess chronotype, restless legs syndrome, and the household sleep environment. Phase 2 involved three additional questionnaires to assess sleep quality, daytime sleepiness and insomnia symptoms, as well as two sleep devices. Participants wore a wrist activity monitor to assess sleep–wake patterns and light levels for 7 days and a home sleep apnea test for 1 night. A subset also had devices objectively record light, temperature, and sound levels in their bedrooms for 7 days. Sample sizes ranged based on assessment from 2200 to 2400, completing Phase 1 questionnaires, 899 with valid wrist actigraphy data, and 619 with a valid sleep apnea test. The data will be part of the full CARDIA dataset, which is available to researchers.