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They say you're only as old as you feel, but dealing with sleepless nights can make you feel ancient. Having to face the day when you've had no rest is challenging, but getting older really can negatively affect your sleep. You may now find yourself waking up at the crack of dawn, or struggling to sleep through the night. And achieving a lie-in at the weekends could be a rarity.

It's usual to have several changes in your sleep patterns when you get older, explains Dr Marina Ezcurra, lecturer in the biology of ageing at University of Kent.

"The total time we spend sleeping often decreases, as does the quality of sleep," she says. "As we age, many of us find it takes longer to fall asleep, our sleep becomes more fragile, and we wake up more often."

At the same time, feeling more tired in the daytime and needing to nap are common in older people. Of course, not everyone is affected in the same way as they age. Some older people have no problem sleeping at all, while others really struggle with insomnia.

Why does sleep get worse with age?

There are a number of reasons that sleep may get harder as you get older, says sleep behaviour practitioner James Wilson, the 'Sleep Geek'. "We become more sensitive to stress, to koffein, och alkohol. We get more aches and pains. And for women, menopaus can cause significant issues around sleep."

Studying animals has helped us learn more about sleep and ageing in humans, says Ezcurra. Scientists now know that sleep and wakefulness are regulated by the brain. The brain releases chemicals which fire when we are awake but are almost silent during sleep. While chemicals that promote sleep are released at times of rest.

"Researchers have discovered a 'sleep-wake flip-flop' mechanism regulating sleep and wakefulness, where the wake-promoting and sleep-promoting neurons [brain cells] inhibit each other, creating rapid transition between sleep and wake states," explains Ezcurra.

Ageing appears to affect this sleep-wake system, by reducing the number of chemicals that promote sleep, making it harder to get enough rest as you get older.

Physiologist, Samantha Briscoe, puts it another way. Older people tend to feel sleepier earlier in the evening and wake earlier in the morning compared to younger adults. This may be due to lower amounts of a sleep-promoting hormone called melatonin being produced in the brain.

"Throughout the night our sleep transitions through various stages - light sleep, deep sleep, and REM sleep," says Briscoe. "Older people spend more time in lighter stages of sleep and less time in deep sleep - the refreshing part of our sleep. Older people produce less melatonin, meaning they may wake more throughout the night, resulting in more fragmented sleep."

Sleep and dementia

Disrupted sleep is also common in people with age-related brain conditions such as Alzheimer's. But Ezcurra says it's not yet clear if the disease causes sleep problems or if sleep problems increase the risk of conditions such as demens.

"Researchers are studying if sleep dysfunction makes the brain more vulnerable to neurodegenerative disease processes," she says.

Improve your sleep habits

If you've found your sleep has got worse as you've got older, there are lots of things you can try to improve the chances of getting enough rest.