A UK device-based prospective study suggested that irregular sleep was associated with higher risk of major adverse cardiovascular events (MACE), regardless of whether individuals met sleep duration recommendations or not. The study included 72 269 individuals aged 40–79 years and followed for 7.8 years, without a previous history of MACE and without an event in the first year of follow-up. The sleep was accelerometer-measured. The Sleep Regularity Index (SRI), a metric that captures day-to-day variability in bedtime, wake-up time, sleep duration, and awakenings during sleep, was assessed using a validated open-source algorithm and categorized as irregular (SRI <71.6), moderately irregular (SRI between 71.6 and 87.3), and regular (SRI >87.3 [reference group]). Irregular (Hazard Ratio [HR] 1.26) and moderately irregular (HR 1.08) sleepers were at higher risk of MACE compared with regular sleepers. Dose-response analyses treating SRI as a continuous measure showed that SRI was associated with MACE risk in a near-linear fashion, with a steeper MACE risk reduction at higher (better) SRI scores. Joint SRI and sleep duration analyses showed that meeting the age-specific sleep duration recommendation offsets MACE risk for moderately irregular sleepers (HR 1.07), but not for irregular sleepers (HR 1.19). Circadian misalignment, resulting from sleep irregularity, disrupts the synchronization between the internal biological clock and external environmental cues, potentially leading to adverse health effects. Source: https://jech.bmj.com/
