A major new study published this week has reframed how researchers think about sleep and long-term health. It's not just about clocking enough hours, it's about which stage of sleep you're actually getting, and how often your sleep gets interrupted along the way. Here's what the study found, and what it means for a wind-down routine.
The study, in brief
Researchers led by Shengzhi Sun of Capital Medical University analysed data from 95,559 UK Biobank participants who wore wrist accelerometers for seven consecutive nights. A deep-learning algorithm calculated each person's sleep stages (REM, deep, and light sleep), total sleep duration, wakefulness after falling asleep, and how irregular their sleep pattern was night to night. Participants were then followed for a median of 8.9 years, with health records checked against more than 1,000 disease outcomes, published September 17th in PLOS Medicine.
REM sleep mattered most broadly
Greater REM (dream) sleep was associated with a lower risk of 83 separate diseases, including a 26 percent lower risk of heart failure, a 46 percent lower risk of dementia, and an 80 percent lower risk of Parkinson's disease, comparing higher and lower REM sleep amounts. REM sleep turned out to be linked to a far broader range of health outcomes than any other single sleep measure in the study.
Deep sleep mattered for a smaller, specific set
Greater deep sleep was linked to a lower risk of seven conditions specifically, including type 2 diabetes and major depressive disorder. A more targeted effect than REM sleep, but a meaningful one for the conditions it touched.
The other half of the story: disrupted sleep raises risk
Beyond the sleep stages themselves, greater night-to-night sleep irregularity and more wakefulness after initially falling asleep were each linked to a higher risk of several conditions, including anxiety and substance use disorders. Total sleep also mattered at the extremes, less than 5 hours a night was associated with meaningfully higher disease risk, while 6 to 8 hours was linked to the lowest risk overall.
An important caveat
The researchers were careful to flag that some of these links may run in the opposite direction to how they first appear, a pattern called reverse causation. Depression is the clearest example: disrupted sleep is a well-known symptom of depression, so it may be that low mood is driving the poor sleep in some cases, rather than poor sleep alone causing the depression. This is an observational study, not proof of direct cause and effect.
Where GoCalm™ and the Comfort Sleep Mask fit in
Two of the specific measures this study flagged, wakefulness after falling asleep and night-to-night irregularity, are exactly what a consistent, screen-free wind-down and a genuinely dark room are designed to address. GoCalm™ supports getting back to sleep faster if you do wake during the night, reducing that time spent lying awake. The Comfort Sleep Mask blocks out light that can otherwise fragment sleep stages and cause the kind of disrupted, irregular sleep the study associated with higher risk.
Helps you get back to sleep faster, reducing time spent awake in the night.
Blocks light that can fragment sleep stages and disrupt REM and deep sleep.
The key findings at a glance
| Measure | Association |
|---|---|
| More REM sleep | Lower risk of 83 diseases, including heart failure, dementia, Parkinson's |
| More deep sleep | Lower risk of 7 conditions, including type 2 diabetes, depression |
| More wakefulness after falling asleep | Higher risk of several conditions, including anxiety |
| Under 5 hours total sleep | Higher overall disease risk |
Frequently asked questions
Does this mean I need to start tracking my REM sleep?
Not necessarily. This was a research study using specialised wrist accelerometers and algorithms, not a claim that everyone needs a consumer tracker. Focusing on consistent, undisturbed sleep is the practical takeaway, not obsessive tracking.
Does disrupted sleep cause anxiety, or does anxiety cause disrupted sleep?
The study's authors specifically noted this could run in either direction, and likely does for some people. This research shows an association, not proof that one directly causes the other.
Is GoCalm™ a treatment for any of these diseases?
No. GoCalm™ and the Comfort Sleep Mask support a calming, undisturbed sleep routine, they do not diagnose, treat, or prevent heart failure, dementia, Parkinson's disease, diabetes, or any other medical condition.
What's the single biggest takeaway?
Getting enough hours matters, but so does minimising disruption. Time spent awake during the night and irregular sleep patterns were linked to real health risks in this study, alongside total sleep duration itself.
Support undisturbed sleep, not just more hours of it
A calming wind-down and total darkness, together.
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