Overview
- Researchers at the University of Oulu analyzed 3,231 adults from the Northern Finland Birth Cohort 1966 using one week of wearable sleep data at age 46 and more than 10 years of registry follow-up.
- Large night-to-night swings in when people went to bed, and in the midpoint of their sleep, were tied to roughly a twofold rise in major heart events among shorter sleepers.
- Variability in wake-up time did not show a clear link to future cardiac problems.
- The study reported hazard ratios of 2.01 for irregular bedtimes and 2.00 for irregular sleep midpoints among participants averaging under eight hours of time in bed.
- Major adverse cardiac events included heart attack, unstable angina, stroke, heart-failure hospitalization, or cardiovascular death, with 128 people—about 4%—affected during follow-up; the authors note the single-cohort design and one week of sleep measurement limit certainty about causation.