📅 Last reviewed: July 2026 · MySleepTool Editorial Team
Sleep Regularity Calculator
Score your sleep consistency — research published in 2026 shows that sleep regularity predicts cardiovascular health and quality of life better than sleep duration alone.
Enter your sleep and wake times for the past 7 nights (leave blank if you didn't sleep or don't remember).
📋 Consistency recommendations
The Sleep Regularity Index — What New Research Shows
A study published in the Journal of Sleep Research in April 2026 examined 768 middle-aged to older adults and found that sleep regularity (measured by the Sleep Regularity Index) was significantly associated with physical and mental health-related quality of life — independent of total sleep duration. This adds to a growing body of evidence suggesting that when you sleep matters as much as how long you sleep. The same research group has previously shown that irregular sleep is associated with higher cardiovascular disease risk and mortality compared to consistent sleep timing, even when total hours are equivalent.
What Is the Sleep Regularity Index?
The Sleep Regularity Index (SRI) was developed by Andrew Phillips and colleagues and measures the probability that any two points in time 24 hours apart share the same sleep/wake status. An SRI of 100 means perfectly consistent sleep timing every day. An SRI of 0 means completely random, unpredictable sleep timing. Most healthy adults with regular schedules score 75–90. People with shift work, irregular schedules, or significant social jet lag often score 50–70.
How much does weekend sleep variability matter?
Significantly — this is called "social jet lag" and is associated with worse metabolic health, higher BMI, elevated cardiovascular risk markers, and worse mood. Even a 1-hour shift in sleep timing between weekdays and weekends produces measurable biological effects. A 2-hour shift (common in night owls who sleep in on weekends) is associated with a 66% higher risk of metabolic syndrome in large epidemiological studies. Keeping wake times consistent within 45 minutes across all days is the most evidence-supported single habit for sleep health.
Is consistent late sleep better than irregular early sleep?
For regularity — yes. A consistent 1 AM bedtime every night is better for health than alternating 10 PM and 2 AM bedtimes, even though the early bedtime is individually healthier. This reflects two separate variables: timing (early vs late) and regularity (consistent vs variable). The healthiest pattern is consistently early. The second healthiest is consistently late. The least healthy is irregular timing regardless of the clock time.
📋 Reviewed by MySleepTool Editorial Team · July 2026 · Sources: Sansom K et al. "Health Related Quality of Life and Sleep Regularity Among Middle-Aged to Older Adults" Journal of Sleep Research (April 2026). Educational purposes only.