When most people think about sleep and health, the conversation usually ends at “get 7–9 hours per night.” But emerging science is showing us that when we sleep—and how consistent we are with our timing—may matter just as much, if not more, than duration.

A 2024 study (PMID: 37738616) brought new clarity to this. Using accelerometer data from over 60,000 adults followed for six years, the researchers asked a simple but profound question:

Is it the number of hours you sleep, or the regularity of your sleep schedule, that predicts long-term health?

What the study found

Instead of measuring only duration, the team calculated a Sleep Regularity Index (SRI), which captures how consistent someone’s sleep and wake times are across days.

The results were powerful:

• People with the most regular sleep schedules had a 20–48% lower risk of all-cause mortality.

• They also had a 16–39% lower risk of cancer mortality.

• And a 22–57% lower risk of cardiometabolic mortality (heart disease, stroke, diabetes).

• When compared head-to-head in statistical models, sleep regularity outperformed average sleep duration as a predictor of survival.

In short: it’s not only about getting “enough sleep.” It’s about getting it at the same times every day.

Why rhythm matters for the body

The human body runs on circadian rhythms—24-hour biological cycles that regulate nearly every system:

• Hormones like cortisol, melatonin, and growth hormone

• Metabolism and insulin sensitivity

• Immune function and inflammation

• Cellular repair and gene expression

Irregular sleep disrupts these rhythms, much like constant jet lag. That internal misalignment stresses the cardiovascular system, destabilizes blood sugar, and weakens immune defenses. Over years, those small disruptions accumulate into higher risks of chronic disease and earlier mortality.

In contrast, consistent sleep acts like an anchor. It helps the circadian system “know what to expect,” creating stability across other biological processes.

The bigger picture for healthspan

What strikes me most about this study is how simple the intervention is. We talk endlessly about high-tech biohacks—wearables, supplements, longevity drugs. But here we see evidence that one of the strongest predictors of survival might be something as basic as:

• Going to bed at roughly the same time each night 

• The earlier you go to bed the better (latest 10pm)

• Waking up at a consistent hour

• Keeping that rhythm steady, even on weekends

No device, no prescription—just discipline.

And this aligns with the broader theme of healthspan: longevity is built not on single dramatic interventions, but on small, rhythmic habits done consistently over time.

Limitations to note

Of course, no study is perfect.

• This analysis was based on a middle-aged to older UK cohort, so generalization to younger populations remains to be tested.

• Accelerometers can measure timing and duration, but they can’t assess subjective sleep quality (restfulness, dreams, or recovery states).

• Causation cannot be fully established—though the strong associations make a convincing case.

Even with these limitations, the large sample size and rigorous follow-up make this one of the strongest datasets we have linking sleep rhythm with survival outcomes.

What this means for us

If you want to extend not only your lifespan but your healthspan, start small. You don’t need to overhaul your entire sleep life overnight. Instead:

• Pick a realistic bedtime and stick to it—even on weekends.

• Wake up at the same time daily, letting light exposure help cue your rhythm.

• Treat consistency as the real “sleep supplement.”

Closing thought

This study makes me pause. For all the complexity of modern medicine, sometimes the answers lie in what seems almost too simple. Rhythm. Consistency. The body thrives on them.

👉 How regular is your sleep? Do you notice a difference in your energy, focus, or health when you keep to a strict rhythm versus when you don’t?

I’d love to hear your thoughts and strategies.