Experts have warned that some of the telltale signs of dementia could appear in the middle of the night. Symptoms that affect your sleep could indicate cognitive decline before you notice other warning signs.

Dementia is a syndrome, or a group of symptoms, linked to the ongoing decline of the brain. Most common in people over the age of 65, symptoms such as memory loss can often be mistaken for normal signs of getting older.

But your sleeping habits could also be affected. The Alzheimer’s Society explains that people with dementia may experience certain sleeping problems.

On its website, the charity said: “A person with dementia experiences physical changes in their brain because of their condition. These changes can affect how much, and how well they sleep.

“A person with dementia may have problems with sleeping at night, and may sleep more during the day. They may find it difficult to get to sleep or they may wake up in the night. The person you care for may not feel well rested when they wake up.

“Over time, if these problems happen often, poor sleep may make the symptoms of dementia worse. You may find this difficult to cope with.”

It continued: “For a person with dementia, getting enough sleep can be a challenge. Sleeping well can be difficult for a person aged over 55, as the parts of the brain that control sleep may not work as well. An older person is likely to go to sleep earlier and may have difficulty sleeping through the night as much as they used to.”

According to the society, a person with dementia might:

• Have difficulty getting to sleep
• Wake up several times during the night
• Sleep less deeply
• Sleep for less time overall.

They may also sleep more in the day and have difficulty sleeping at night. “This process can start to happen even before a person has dementia, or if they have mild cognitive impairment (MCI),” the charity added.

A recent study, published in the journal Neurology, found that your sleeping habits could predict your likelihood of developing dementia in advance. Researchers found that people who are increasingly sleepy throughout the day, and may take “excessive” naps, are twice as likely to develop dementia.

Over a period of five years, the 733 study participants were categorised into three groups:

• Stable sleep (SS) - stable or slightly improved sleep, which 321 women (43.8%) demonstrated
• Declining nighttime sleep (DNS) - decreases in nighttime sleep quality and duration, moderate increases in napping, and worsening circadian rest-activity rhythms (RARs), which 256 women (34.9%) demonstrated
• Increasing sleepiness (IS) - large increases in both daytime and nighttime sleep duration and quality, as well as worsening circadian RARs, which 156 women (21.3%) demonstrated.

After five years, the team also established whether participants had normal cognition, mild cognitive impairment, or dementia. This was based on either multiple neuropsychological tests, physician diagnosis, or admission to a residential nursing home care.

Among the women in their 80s, 164 (22.4%) of them developed mild cognitive impairment and 93 (12.7%) developed dementia. It was found that women in the increasing sleepiness group had approximately double the dementia risk of those with stable sleep profiles.

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Study authors wrote: “Among community-dwelling women in their 80s, those with increasing 24-hour sleepiness over five years had doubled dementia risk during that time. Change in multidimensional 24-hour sleep-wake activity may serve as an early marker or risk factor for dementia in oldest old women.”

Further to this, one study, published in Alzheimer’s and Dementia journal in 2016, revealed that high or low sleep duration increased risk of cognitive impairment and dementia. Another, published in Nature Communications journal in 2021, showed that shorter sleep duration in middle age was linked with a higher dementia risk.

The NHS lists the “common” early signs of dementia as:

• Memory loss
• Difficulty concentrating
• Finding it hard to carry out familiar daily tasks, such as getting confused over the correct change when shopping
• Struggling to follow a conversation or find the right word
• Being confused about time and place
• Mood changes

If you or someone you know is experiencing dementia symptoms, you should speak to a GP.