- A new large-scale study investigates the associations between sleep duration and disease risk.
- Participants wore wrist accelerometers for 1 week to assess not only their sleep duration, but also how long they spent in different phases of the sleep cycle.
- Among other findings, the researchers showed that more dream sleep was associated with a reduced risk of more than 80 health conditions.
- Overall, people who slept for 6–8 hours had the lowest risk of health issues.
A new study, published in PLOS Medicine, analyzed real-world data from almost 100,000 participants in the UK Biobank databank.
They found that greater rapid-eye movement (REM, or dream) sleep was associated with a lower risk of 83 diseases, while deeper sleep was associated with a lower risk of seven health conditions.
Although previous studies have linked short sleep duration with disease and an
This is not ideal. People can misremember, and we are not always aware of when we actually drop off or wake up during the night.
Also, self-reported sleep duration provides no information about time spent in sleep stages, such as deep sleep and REM sleep.
In the current study, scientists used wrist-worn accelerometers to gather much more detailed information about participants’ sleep stages, plus how long they slept for and how irregular their sleep patterns were.
Why do we need sleep anyway?
We all sleep. It’s one of those fundamentals that is so common, not just in humans but throughout the animal kingdom, that we often give it very little thought.
However, the fact that animals lie unconscious for hours every day in a world full of predators suggests that it must be doing something vital to have been preserved throughout evolutionary history.
What is sleep for? Now that is a question that scientists are still grappling with. We know we need it, we know it is important, but the precise functions of sleep are still being sketched out.
Most scientists, however, believe it likely conducts a wide range of roles, including solidifying memories, clearing up metabolic detritus from the brain, allowing the gut microbiome to rest, repair, and clean up, and supporting immune health.
Whatever their roles, what scientists do know is that good quality sleep is vital for long-term health.
The latest study on sleep takes a detailed look at the relationships between sleep and disease outcomes over almost 10 years of follow-up.
Looking for links: Sleep and illness
In total, the study analyzed data from 95,559 adults in the United Kingdom with an average age of 56.2 years.
After wearing the accelerometer for 1 week to assess their sleep quality and quantity, they were followed for a median period of 8.9 years until the onset of a health condition or death.
The scientists found that increased REM sleep at baseline was associated with a reduced risk of more than 80 health conditions, including:
- heart failure
- hypertension (high blood pressure)
- atrial fibrillation
- ischemic heart disease
- Parkinsonism
- multiple sclerosis
- dementias.
Meanwhile, increased amounts of deep sleep were associated with a reduced risk of seven diseases, including:
- type 2 diabetes
- major depressive disorder
- sleep apnea
- Parkinson’s disease.
Importantly, the authors note that the links to some of these health conditions might be due to “reverse causation.”
Depression is a good example of this: Disrupted sleep is a common
In contrast to deep sleep, greater time spent in light sleep — a sign of poorer quality sleep — was associated with a higher risk of conditions, such as major depressive disorder, but a lower risk of others, like heart failure and cellulitis.
The scientists also evaluated a measure called wakefulness after sleep onset (WASO). This measures the total amount of time an individual is awake after having initially fallen asleep. In other words, it is a marker for sleep irregularity.
A higher WASO score was associated with an increased risk of six conditions, including:
- psychoactive substance dependence
- alcohol abuse
- osteoarthritis.
Additionally, the scientists investigated irregular sleep patterns and found that they were associated with an increased risk of:
- abdominal pain
- anxiety
- major depressive disorder.
A longer overall sleep duration was associated with a lower risk of no less than 50 conditions, such as:
- protein-calorie malnutrition
- acidosis
- type 2 diabetes.
Overall, the researchers conclude that 6–8 hours of sleep is the optimal amount, which is slightly different from the more commonly quoted
Sleep tips from sleep experts
For those who struggle to get the sleep they need, these results may feel concerning. SW, Medical News Today reached out to some experts in the field and asked for practical advice.
Firstly, Scott Nass, MD, a board-certified family medicine physician and lead physician at SwiftCareMD, suggested keeping a consistent wake-up time.
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“Getting up roughly at the same time every day allows your brain to organize the pattern of when you are awake and when you require your body to fall prey to the desire to drop off,” Nass, who was not involved in the recent study, told us.
I have explained that this routine should be continued during the weekend.
“Lying in for a few hours after a difficult night can feel rewarding,” he continued. “But really, it is only shifting your sleeping pattern out, putting obstacles in your brain during evening time.”
He also said that “morning daylight taken soon after rising and with the sun in your vision will only help solidify this routine in your mind.”
Secondly, I have suggested people “stop struggling with sleep in bed.” He told us that “repeatedly going to bed awake and anxious about sleeping can make the brain associate the bed with frustration and alertness.”
Instead, I have recommended “stepping away from the bed for 15-20 minutes, going to a quiet, dim room, and doing something calming away from distractions.” Then, try sleeping again only once tiredness returns.
Chelsie Rohrscheib, PhD, head sleep expert and neuroscientist at Wesper, also not involved in the study, spoke of the importance of maintaining a quiet, dark, and cool (65–70 degrees Fahrenheit) bedroom.
This is because “your core body temperature needs to drop to initiate and maintain sleep.” Reducing bedroom light, she suggested, can be attained “by using blackout blinds or an eye mask.”
Rohrscheib also related the importance of “a pre-bedtime routine focusing on relaxing, low-light activities for at least 30 to 60 minutes before sleep to help your brain and body relax and prepare for sleep.”
“This may include activities like light reading, listening to relaxing music, a warm bath, meditation, or deep breathing exercises. You should also avoid stimulating activities, such as watching media or using your mobile phone.”
–Chelsie Rohrscheib, PhD
Additionally, she advised people to avoid:
- electronic screens at least 60 minutes before bed
- caffeine after 3 pm
- consuming heavy meals less than 2 hours before bedtime.
Finally, Rohrscheib emphasized the importance of “getting at least 30 minutes of heart rate-raising exercise per day to use up excess cortisol stores, since cortisol is extremely awake-promoting and can reduce sleep quality.”
