Sleep Consistency > Sleep Duration
We’ve all heard that getting “8 hours of sleep” is the number to reach. But new research suggests that when you sleep may matter even more than how long you sleep. Kristen Holmes, WHOOP’s Principal Scientist and Vice President of Performance Science, has been leading research showing that sleep consistency (going to bed and waking up at the same times every day), is a key factor for physical performance, mental health, and long-term resilience.
Sleep Consistency
Our bodies run on circadian rhythms, which are 24 hour biological clocks that regulate hormones, metabolism, and brain function. When we keep a regular sleep–wake cycle, our circadian system strengthens, making it easier to fall asleep, stay asleep, and feel alert during the day.
Holmes’s research with WHOOP data shows that even a one hour difference in bedtime or wake time can throw off recovery markers like resting heart rate and heart rate variability (HRV). These small disruptions add up over time, leaving feelings of grogginess, less focus, and more vulnerability to stress.
Sleep and Mental Health: The Army Study
One of the most fascinating studies followed 862 U.S. Army soldiers stationed in Arctic Alaska. Soldiers who kept more consistent sleep schedules (even when their total hours of sleep were lower) had:
• Higher resilience at work
• Stronger social connections
• Less homesickness
• Better overall mental health
Meanwhile, those with irregular sleep patterns, especially in the summer months when natural light exposure disrupted their sleep environment, struggled more with psychological functioning. This shows us that consistency is not just a performance hack, it can serve as a mental health necessity.
Why Sleep Duration Alone Isn’t Enough
Sleep quantity matters. But, if you sleep 8 hours one night, 5 hours the next, and 10 the following, your body can’t reap the full restorative benefits. In fact, WHOOP’s data shows that people with steady, predictable sleep patterns often feel and perform better than those who log longer but irregular hours.
Think of it like training: one great workout won’t make you fit if the rest of the week is random and inconsistent. Sleep works the same way.
Practical Ways to Improve Sleep Consistency
Kristen Holmes’s research and practical strategies come down to a few key habits:
1. Set a consistent sleep and wake time - and stick to it, even on weekends/days with less structure.
2. Get morning sunlight within an hour of waking to reinforce circadian rhythms.
3. Reduce evening light exposure, especially blue light from screens, in the 2 hours before you go to sleep.
4. Keep your sleep environment cool, dark, and quiet.
5. Take control of your evenings, develop a short, repeatable routine that signals your brain it’s time to wind down.
Tips for Shift Workers
Not everyone has the luxury of a standard 9-5 schedule. Shift workers face unique challenges when it comes to sleep. Here are some strategies that could help:
• Prioritize consistency within your schedule. Even if your “night” is during the day, try to keep your sleep wake window as regular as possible across shifts.
• Use light strategically. Get bright light exposure when you need to be alert (before or during your shift), and block light when it’s time to sleep (blackout curtains, sleep masks, or blue light blocking glasses on your way home).
• Create a sleep friendly environment. Keep your room dark, cool, and quiet with blackout curtains, white noise machines, etc.
• Nap purposefully. Short naps (20–30 minutes) before or during long shifts can help boost alertness without causing grogginess.
• Protect recovery days. On days off, avoid flipping your schedule back and forth too drastically. Instead, aim for a compromise that lets you recover while maintaining some rhythm.
• Keep consistent routines. Everyone benefits from consistent routines: a short bedtime routine, the same wake up routine, and exposure to light at the same times relative to your schedule.
Why This Matters Tonight
Most of us will spend about a third of our lives asleep. But instead of thinking of sleep as wasted time, think of it as the foundation that supports every waking moment. By committing to consistency, you’re not just improving tonight’s sleep/restorative functions, you’re strengthening your body’s ability to handle stress, perform, and connect with others tomorrow.
Challenge yourself: pick a bedtime, set an alarm for the morning, and keep it consistent for the next week. Track how your energy, mood, and how your workouts feel; chances are, the results may surprise you.
Sleep isn’t just about more hours. It’s about stable, repeatable rhythms. As Kristen Holmes’s work shows, sleep consistency is one of the most powerful levers we have for better physical and mental performance, stronger health, and a more resilient mind.
