Sleep of 6 to 8 hours was linked to lower disease risk, and REM sleep stood out

If you have ever wondered whether the kind of sleep you get matters as much as the hours, this study has an answer worth hearing. In a study of 95,559 middle-aged and older adults, more REM sleep, the stage linked to dreaming, was linked to a lower risk of 83 diseases, and the lowest risks for many conditions fell in the 6 to 8 hour range.

So your hunch is right. REM counts, and it counts a lot. Here is what the researchers found and how to think about it.

How the study worked

Researchers followed 95,559 adults in the UK Biobank, a large health project, who wore a wrist device that tracks movement. A computer program (called SleepNet) used that movement data to estimate their sleep stages, how long they slept and how steady their sleep was, then followed them for years to see who developed disease, as reported in PLoS Med on September 17, 2026. This was an observational study, so it shows links and cannot prove that sleep itself causes the differences.

What they found

The team looked at 1,049 health outcomes. Sleep patterns were linked to the risk of 156 of them. People were followed for a median of 8.9 years.

The stages told different stories:

• REM sleep: people with more REM sleep had a lower risk of 83 diseases. That was the biggest number of any sleep measure.
• Deep sleep: people with more deep sleep had a lower risk of 7 diseases.
• Irregular sleep: people whose sleep schedule varied more had a higher risk of 3 diseases.
• Waking up in the night: people who spent more time awake after falling asleep had a higher risk of 6 diseases.

Then came the hours. For 86 conditions, the link with sleep length was not a straight line. More sleep was not always better, and less was not always worse. For 69 of those conditions, the lowest risk sat mostly in the 6 to 8 hour window.

The short end stood out most. People who slept under 5 hours had the widest set of differences compared with people in the 6 to 8 hour group. They accounted for 37 of the 41 significant higher-risk links the study found.

The authors also noted that people who slept 6 to 8 hours tended to have a more favorable sleep architecture. That is a plain way of saying the mix of sleep stages through the night looked better.

What does REM sleep have to do with it?

Your night is made of stages that repeat in cycles. Light sleep comes first, deep sleep is the heavy, restful stage, and REM is the stage where most vivid dreaming happens.

This study did not test how to get more REM. What it did show is that REM and the 6 to 8 hour window go together. People in that range had a better stage mix, and more REM was the stage most often linked to lower disease risk. For most of us, that makes enough time in bed the practical starting point.

What you can do today

Pick a wake-up time you can keep every day, even on weekends. Then count back 8 hours and set a phone alarm for bedtime, so you have room to land in the 6 to 8 hour window. A steady schedule also speaks to the irregular sleep the study linked to higher risk. Try it for a week and notice how you feel.

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