Level 1 — Absolute Beginner
Scientists studied sleep in a very big group. About 95,000 people took part. They wore a watch on the wrist for one week.
The watch showed how long each person slept. It also showed the different kinds of sleep. One kind is called REM sleep. In REM sleep, people have dreams.
The scientists watched the people for about nine years. People with more REM sleep got fewer diseases. This included 83 different diseases.
The study cannot prove that REM sleep stops disease. But it shows a strong link. Most people need about six to eight hours of sleep.
- scientist
- A person who studies the world with tests.
- sleep
- The rest your body gets at night.
- dream
- Pictures and stories in your mind while you sleep.
- disease
- A sickness.
- wrist
- The part of the arm next to the hand.
- study
- A careful test to learn something.
- link
- A connection between two things.
- hours
- Units of time. One hour is 60 minutes.
Level 2 — Elementary
A new study in the journal PLOS Medicine says people who spend more time in REM sleep, the dreaming stage, have a lower risk of many diseases.
Researchers from Capital Medical University in China used data from 95,559 people in the UK Biobank project. Each person wore a wrist tracker for seven days and nights. A computer program used the movement data to guess when they were in light, deep or REM sleep.
After about nine years, the team looked at more than a thousand health conditions. More REM sleep was linked to a lower risk of 83 of them, including dementia, heart failure and Parkinson's disease. More deep sleep was linked to lower risk of type 2 diabetes and depression.
The study shows a link, not proof. Still, the results agree with advice to sleep about six to eight hours a night.
- journal
- A magazine where scientists publish research.
- tracker
- A device that records information about your body.
- dementia
- A disease that damages memory and thinking.
- risk
- The chance that something bad will happen.
- deep sleep
- The stage of sleep when the body rests most.
- condition
- A health problem.
- diabetes
- A disease that affects blood sugar.
- proof
- Facts that show something is definitely true.
Level 3 — Intermediate
A large study published on September 17 in PLOS Medicine reports that people who spend more of the night in REM sleep, the stage most associated with vivid dreams, face a lower risk of dozens of diseases.
A team led by Capital Medical University in China analysed 95,559 participants in the UK Biobank who wore wrist accelerometers for seven consecutive days and nights. A deep learning algorithm converted their movement into estimates of REM, deep and light sleep, total duration, waking after sleep onset and night to night irregularity.
With a median follow up of nearly nine years, each additional 47.6 minutes of REM sleep was linked to lower risk of 83 conditions. The associations were strong for dementia, with a hazard ratio of 0.54, for heart failure at 0.74 and for Parkinson's disease at 0.20. More deep sleep was tied to lower risk of type 2 diabetes and major depression, and about six to eight hours of total sleep looked best.
Because the work is observational, it cannot show that REM sleep protects the body. Poor health may itself disturb sleep, and wrist devices only estimate sleep stages.
- accelerometer
- A sensor that measures movement.
- algorithm
- A set of rules a computer follows to solve a problem.
- irregularity
- Lack of a steady pattern.
- median
- The middle value in a set of numbers.
- follow up
- The period during which participants are tracked after a study begins.
- association
- A statistical link between two things.
- hazard ratio
- A number comparing the risk of an event between two groups.
- observational
- Based on watching what happens rather than running an experiment.
Level 4 — Advanced
A sweeping analysis published on September 17 in PLOS Medicine has found that people who log more time in REM sleep, the phase most closely tied to vivid dreaming, appear to face a diminished risk of dozens of illnesses, from dementia to heart failure.
Researchers led by Capital Medical University in China drew on 95,559 UK Biobank volunteers who wore wrist accelerometers for a week. A deep learning algorithm translated the movement traces into estimates of REM, deep and light sleep, overall duration, wakefulness after sleep onset and night to night irregularity, which were then set against more than a thousand diagnoses over a median follow up of almost nine years.
Each increment of 47.6 minutes of REM sleep was associated with lower risk across 83 conditions, with hazard ratios of 0.54 for dementia, 0.74 for heart failure and a striking 0.20 for Parkinson's disease. Deeper sleep correlated with reduced risk of type 2 diabetes and major depression, while roughly six to eight hours of total sleep sat at the protective sweet spot.
The authors and independent commentators are careful to stress that these are correlations. Early disease may erode REM sleep long before diagnosis, a phenomenon known as reverse causation, and consumer grade sensors infer sleep architecture indirectly. Establishing whether protecting REM sleep can actually forestall illness will require trials rather than observation alone.
- sweeping
- Wide in scope.
- diminished
- Made smaller or less.
- increment
- A small step up in amount.
- correlate
- To have a mutual relationship or connection.
- erode
- To gradually wear away.
- reverse causation
- When the outcome actually causes the supposed cause.
- architecture
- The structure or organization of something.
- forestall
- To prevent by acting first.
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