By Anthea Rowan
This is the 66th instalment in a series on dementia, including the research into its causes and treatment, advice for carers, and stories of hope.
In the last years of her life, my mother began to have nightmares. One recurred from time to time and became a metaphor for the dementia that, in the end, took her life. In it, she was trapped on a ship and could not get off.
Once, while staying with my sister, mum began to crash around her room in the night. When my sister went to investigate, she found our mother trying to get off her ship. On another occasion, while with me, she clambered on top of the toilet, again to get off the ship. She fell backwards, cracking her head on the floor, and required stitches.
My mother’s nightmares could have been linked to Alzheimer’s disease, according to a 2024 study by a team at Boston University in the US state of Massachusetts. It found that cognitive impairment had a correlation with higher nightmare frequency and distress in the elderly.
However, Dr Abidemi Otaiku, a neuroscientist at Imperial College London, says that nightmares can be a marker of earlier dementia – and even a driver of it.
His findings have shown that frequent or persistent nightmares may be an easily identifiable marker of dementia risk, one that can be detected even in the first decade of life. Other risk factors for dementia, such as diabetes and hypertension, typically only surface from middle age, he says.
Otaiku’s latest study – he has contributed to a number in this area – found that people who have regular nightmares as children are three times more likely to die before the age of 70 than those who rarely have them.
The reason is that nightmares contribute to whole-body ageing, not just brain disease and brain ageing.
The culprit is the stress hormone, cortisol.
Otaiku says that cortisol has a direct effect on brain structures linked to cognition and Alzheimer’s disease, such as the hippocampus. Studies have shown that cortisol can cause the hippocampus to shrink, which eventually leads to the worsening of our memory.
Do we perceive stress when we are asleep, though?
“Our sleeping brains cannot distinguish between dreams and reality,” Otaiku says. “Therefore, when we experience a threatening scenario during our nightmares, our brains react as if it were actually happening in the real world. This can lead to a powerful stress response, and therefore a significant rise in cortisol levels.”
Having bad dreams is not all bad: research suggests that dream sleep is essential to emotional healing.
The late Dr Rosalind Cartwright, a neuroscientist at Rush University in the US state of Illinois who was dubbed the “Queen of Dreams”, was a pioneer in promoting the positive role of dreams in emotional health.
She found that people with clinical depression and post-traumatic stress disorder (PTSD) who dreamed about their difficult emotional experiences typically went on to overcome these mental health issues.
Lydia Chan, an integrative sleep therapist and founder of The Sleep Code practice in Hong Kong, suggests that we might be able to think of our bad dreams as “free overnight therapy”.
Chan says there are a number of triggers for nightmares, and sometimes there are no identifiable reasons for them.
Stress can be “a big one”, and some people are more prone to stress and anxiety.
“Certain mental conditions such as PTSD, depression, generalised anxiety disorder, bipolar disorder and schizophrenia have also been linked to increased nightmares,” she says.
Medical conditions may play a role, such as people with type 1 diabetes having low blood sugar levels at night. One study found this caused more vivid dreams or nightmares.
Ironically, sleep deprivation and insomnia can cause nightmares, Chan says. They can lead to a phenomenon called “REM rebound” where, if you are short of sleep, over time your body starts fighting back by prioritising REM (rapid eye movement) sleep earlier, which can cut into deep sleep, she explains.
This is unlikely to occur if you miss an hour of sleep here and there, but once you have accumulated a 10- to 12-hour sleep deficit in a week, you may find you have much more vivid or anxiety-producing dreams, she adds.
Even eating certain foods or having them at certain times of the day may lead to bad dreams. Some research shows there is some truth to the adage that cheese gives you nightmares. It can cause gastrointestinal discomfort in those with trouble digesting dairy – and that can disrupt sleep and lead to more vivid or negative dreams.
“Sleep is one of those things in life where the more you try to control it, the further you are away from it,” Chan says.
There are, though, steps a sufferer can take to minimise or mitigate their nightmares.
Start by assessing your sleep routine.
A regular sleep schedule is a good lifestyle habit that can help reduce the REM rebound effect that can lead to vivid or anxious dreams.
Avoid stimulants – coffee, spicy foods, alcohol – before bed. Also, “certain medications and supplements such as vitamin B and melatonin, if taken too close to bedtime, can have a stimulating effect on the body and can cause more vivid and emotional dreams”, Chan says.
Avoid watching horror films or reading scary books before bed, Otaiku says, and get treatment for mental health disorders.
People who suffer such debilitating nightmares that their quality of life is affected should see a sleep therapist, Otaiku urges.
Psychological treatments like image rehearsal therapy (IRT) – “the gold standard”, Otaiku says – may help. IRT involves rewriting distressing dreams and adding positive or neutral endings, then rehearsing them.
IRT, Chan explains, works particularly well with individuals with PTSD who have repetitive nightmares.
“Essentially it allows them to rewrite the script of that repetitive nightmare to reduce its intensity and the associated distress.”
Chan offers CBT-i (cognitive behavioural therapy for insomnia) and ACT-i (acceptance and commitment therapy for insomnia) to help individuals overcome sleep challenges.
New research, Otaiku says, even suggests that psychological treatments – like CBT-i – that can reduce nightmare frequency might even slow down how fast we age.
“It raises the possibility that simple and cost-effective methods to reduce nightmares – at any stage of life – might help to slow our ageing and lower our risk of developing age-related brain diseases, like dementia, even Parkinson’s.”
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