Irregular Sleep Timing Linked to Heart Risk

A US study of 10,000 Americans connected night-to-night sleep variation to higher rates of heart disease.

Updated on Nov. 2, 2026 in Sleep Disorders

A rumpled bed with twisted linen sheets in soft early-morning light beside an unlit ceramic lamp on a wooden nightstand. — A US study of 10,000 Americans tracked over six months found irregular sleep timing and variable sleep cycles were linked to higher heart disease risk. AI Illustration. Upload story photo >

Live Poll

Do you think keeping a consistent sleep schedule matters for your heart health?

A US study tracked the sleep of 10,000 Americans for six months and linked variable bedtimes and sleep length to higher heart disease risk. Scientists analysed data on over one million nights of sleep.

Why it matters

The findings suggest that consistency in sleep timing may be a factor in cardiovascular health alongside sleep duration. Sleep irregularity is often linked to later sleep onset on Friday nights or shift work.

Night-to-night sleep timing changes were associated with a 20%-23% higher risk of heart attack, stroke and heart failure in a cohort of 10,000 Americans tracked for six months and followed for four years. Each half hour of sleep length variation was linked to a 29% higher cardiomyopathy risk and 20% higher heart failure risk, while the study does not establish causation.

The details

Participants wore sleep tracking devices for six months, and researchers measured the number of sleep cycles each night, defined as the interval from the end of one REM period to the end of the next. Greater numbers of complete sleep cycles each night were associated with a 28% lower risk of atrial arrhythmia, while an unusually long sleep cycle was associated with a 55% higher risk of heart attack or stroke.

Sleep was tracked for six months among the study participants.
Participants were followed for four years to assess heart issues.
The findings were presented at the American Heart Association Scientific Sessions 2026 in Chicago.

Patient Care

Adults are advised to sleep 7 to 9 hours per night, yet the average British adult sleeps between 6 and 6.4 hours, a gap this research suggests may matter beyond total duration. The study points to regularity of sleep timing as a potential additional factor for cardiovascular health.

Keeping a consistent bedtime and wake time, rather than only hitting a total number of hours, may be worth considering for heart health. Readers who work shifts or stay up late on Fridays may find this pattern especially relevant.