What Happens During Sleep May Matter as Much as How Long We Sleep

Good Morning.

We tend to think of a good night's sleep in terms of hours.

Seven is respectable. Eight is better. Anything less may leave us wondering how we'll feel the next morning.

But the number of hours we spend asleep tells only part of the story.

Throughout the night, the brain moves through different stages of sleep, each with its own patterns of activity. Some are associated with physical restoration. Others appear to play important roles in memory, learning, and emotional processing.

The amount of time we spend in these stages varies, even when the total hours of sleep remain the same.

And those differences may matter for our long-term health.

In a large study involving more than 95,000 adults, researchers examined whether the distribution of sleep stages was associated with the development of disease over time.

They found that people who spent a greater proportion of their sleep in REM, the stage most closely associated with vivid dreaming, tended to have lower risks of numerous health conditions.

The findings raise an intriguing possibility: two people who sleep for the same number of hours may not receive the same benefits from their sleep.

But understanding what this means requires some caution.

The study identified associations, not cause and effect. It remains possible that underlying health conditions influence sleep patterns long before a disease is diagnosed. The researchers also estimated sleep stages using wearable devices rather than the more precise measurements available in a sleep laboratory.

Still, the research points toward something important about how we understand rest.

Sleep is an active biological process. The brain continues working throughout the night, moving through stages that serve different functions. The balance between those stages may offer information about our health that total sleep duration cannot provide.

That doesn't mean we should begin worrying about how much REM sleep we achieved last night. Consumer sleep trackers can offer useful estimates, but their measurements aren't precise enough to make every nightly fluctuation meaningful.

For now, the familiar advice about getting sufficient, consistent sleep remains sound.

What may change is how scientists evaluate what happens after we close our eyes.

We have become accustomed to asking how much sleep we got.

Researchers are beginning to ask a more complicated question: What kind of sleep did we get?

Source: PLOS Medicine, 2026

Longevity

The Long Game
One small thing for a longer life

Today’s Question

Who has been there for you this year, perhaps without knowing how much it meant?

Think of someone whose presence has made a difference in your life. Perhaps it's a friend who always seems to know when to check in.

We don't always recognize how much someone's kindness or dependability means to us until we stop to consider it. And sometimes, the person making that difference has no idea.

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Final Note

This is what we leave you with. A thought to end the day, carry in your pocket, or come back to later. Nothing big. Just something to reflect on.

What We Haven't Imagined Yet

The future holds possibilities you haven't yet imagined.
It's easy to picture the future as an extension of the life we know today.

But experience introduces us to interests we never expected to develop and opportunities we wouldn't have considered.

Some of the things that may eventually matter most to us aren't even on our minds yet.

And there's something wonderful about that.

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