Sleep Irregularity Predicts Heart Events

Analysis of over one million hours of Fitbit sleep data from ~10,300 All of Us participants found that night‑to‑night shifts in sleep timing and modest changes in sleep duration were associated with a substantially higher risk (roughly 20–24%) of serious cardiovascular events. The association was strongest for schedule volatility—suggesting that weekend 'sleep‑ins' and shift‑work patterns may be an independent risk factor beyond total sleep time. — If replicated, this reframes public‑health sleep advice from 'get more sleep' to 'get sleep and keep a regular sleep schedule', with implications for clinical guidance, workplace scheduling, and how consumer wearables are used for prevention.