You really can sleep too much, as scientists reveal most ‘dangerous' number of hours slumber to get a night

The Sun

15-05-2025

WE all know sleep is important - but some new research is making people rethink how much you really need.
Sleeping too much has been linked to poorer brain performance, especially for those with depression.
1
Scientists from the US, looked at nearly 2,000 adults from the Framingham Heart Study to see how sleep affects brain function.
Everyone was free from dementia and stroke, and ages ranged from late 20s to mid-80s.
They found that people who slept longer than what's usually recommended did worse on memory and thinking tests.
This was even more true for people showing signs of depression.
The current National Sleep Foundation guidelines recommend that most adults sleep for between seven and nine hours per night.
Countless studies have shown that both too little and too much sleep can harm your health.
But this new study, published in Alzheimer's & Dementia revealed that too much sleep might also hurt your brain.
The research, led by the University of Texas Health Science Center, found that long sleep - but not short sleep - was linked to poorer overall thinking skills, including problem-solving.
'Long but not short sleep duration was associated with poorer global cognition and specific cognitive abilities like memory, visuospatial skills and executive functions,' said Sudha Seshadri, founding director of the Biggs Institute and senior author of the study.
I spent three days at a sleep retreat - these are the top 7 things I learnt
The link between long sleep and cognitive decline was even stronger in people showing signs of depression, no matter if they were taking antidepressants or not.
'Long-sleepers were more likely to report symptoms of depression,' said Vanessa Young, clinical research project manager and first author of the study.
'Sleep may be a modifiable risk for cognitive decline in people with depression.'
About 90 per cent of people with depression experience sleep problems, with many of them sleeping longer than people without the condition.
This means their sleep patterns could directly affect how well their brain works over time.
'Sleep may be a modifiable risk for cognitive decline in people with depression," Vanessa Young, clinical research project manager, who also worked on the study, added.
The experts say more studies are needed to understand how long sleep affects the brain over time, particularly in people with depression.
For now, they advise aiming for balanced sleep — not too little, not too much — to keep your brain sharp.
How bad sleep affects weight
Previously in The Sun, experts explained how sleep is closely linked with weight.
Disrupts hunger hormones
Ghrelin is a hormone released after the brain signals the stomach is empty, while leptin is released from fat cells to suppress hunger - and tell the brain it's full.
Studies have shown that when you don't get enough shut-eye, the body makes more ghrelin and less leptin - leaving you more hungry.
One study of 12 men led by University of Chicago showed two days of sleep deprivation drove leptin levels in the blood down by 18 per cent, while increasing ghrelin by 28 per cent.
The men reported a 24 per cent increase in their hunger and appetite compared to when they were given two restful nights.
More time to eat
The less you are asleep, the more you are awake. This gives more of an opportunity to eat.
In the modern day world, people are awake for up to 17 hours at a time - 7am till 12pm. It leaves a huge window for being awake and eating.
If you're struggling with both your weight and sleep, try finishing your meals three to four hours before bed time. That might mean limiting your eating window from 9am until 6pm.
Reach for takeaways
If you have a weird sleeping pattern, chances are your eating schedule is also off-whack.
Struggling to sleep can see us turn to convenience - takeaways, ready meals, oven foods and more, whi;e being energised gives us more motivation to cook healthily.
Eat more calories than normal
Studies suggest that the less sleep you get, the more calorie-dense food you choose to eat.
One study in Chicago found that men ate more food at a buffet after four consecutive night's of rough sleep compared with when they were rested.
They consumed around 340 calories more, mostly because they ate more snacks and carbohydrate-rich food.
Researchers from King's College London also found that adults consumed an additional 385 calories – the equivalent of one and a half Mars Bars – on days after they were deprived of kip by combining the results of 11 previous studies.
More desire for food
Foods, especially those high in calories, are more appetising when we are sleep deprived because we subconsciously know they will boost our energy.
A German study showed the lengths sleepy people would go to for calorific snacks using 32 healthy men.
After a normal dinner and either a restful or restless night's sleep, the men were given three Euros to spend on snacks and told to bid the maximum amount they were willing to spend on each item.
When sleep deprived. participants were willing to pay extra for the junk food items - which they were allowed to eat afterwards - suggesting a stronger desire.
Fat storage more likely
Scientists have warned that not getting enough sleep changes how the body deals with food, which could then lead to weight gain.
One study showed that men who ate a large bowl of chilli mac and cheese after four nights of bad sleep reacted differently to the food than those who were well-rested.
Researchers at Pennsylvania State University said blood tests showed lipids (fats) from foods were cleared faster, suggesting they were being stored almost instantly.
The process did not spring back to its normal rate even after the men were given a long night's sleep.