A change in sense of humour has been linked to the development of dementia, a new study suggests.
Researchers found that those who developed dementia were more likely to find events that aren't typically funny, such as a badly parked car or barking dog, hilarious.
It also revealed that those with a specific type of dementia would laugh inappropriately at tragic events on the news or in their personal life.
Researchers at University College London issued questionnaires to friends and relatives of 48 people with Alzheimer's disease and frontotemporal dementia (FTD) - an uncommon type of dementia which is generally associated with personality, behaviour and language.
They asked participants to rate their loved one's liking for different types of comedy - this included slapstick comedy such as 'Mr Bean', satirical comedy such as 'Yes, Minister' or absurdist comedy such as 'Monty Python' - and asked those completing the questionnaire to say whether they had noticed instances of inappropriate humour.
As well as collecting data about current humour preferences, the team asked the friends and relatives to reflect on the past 15 years – before any of the study volunteers received a diagnosis – to identify any shifts in preference.
The findings, which have been published in the Journal of Alzheimer’s Disease, showed that those who developed dementia were more likely to experience a shift in sense of humour early on, rather than memory issues.
The study showed people with behavioural variant FTD (bvFTD) – a particular form of FTD associated with behavioural changes – had an altered sense of humour compared to those with Alzheimer’s disease and healthy individuals.
This included laughing at events others would not find funny.
It also revealed that people with bvFTD frequently laughed inappropriately at tragic events on the news or in their personal life. This did not happen in those with Alzheimer’s.
People with both bvFTD and Alzheimer’s tended to prefer slapstick humour to satirical and absurdist humour when compared with healthy people of a similar age.
Friends and relatives reported seeing these changes on average at least nine years before the start of more typical dementia symptoms.
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Researchers hope their findings will help improve early dementia diagnosis.
Dr Camilla Clark who led the research at the Dementia Research Centre, University College London, said: "We’ve highlighted the need to shift the emphasis from dementia being solely about memory loss.
"These findings have implications for diagnosis – not only should personality and behaviour changes ring alarm bells, but clinicians themselves need to be more aware of these symptoms as an early sign of dementia.
"As well as providing clues to underlying brain changes, subtle differences in what we find funny could help differentiate between the different diseases that cause dementia.
"Humour could be a particularly sensitive way of detecting dementia because it puts demands on so many different aspects of brain function, such as puzzle solving, emotion and social awareness."
Dr Simon Ridley, director of research at Alzheimer’s Research UK, said the study shows we shouldn't just associate memory loss with dementia.
"It highlights the importance of looking at the myriad different symptoms that impact on daily life and relationships," he explains.
"A deeper understanding of the full range of dementia symptoms will increase our ability to make a timely and accurate diagnosis. We need to see larger studies, following people for extended periods of time, to understand how and when changes in humour could act as a red flag for underlying brain changes.
"Dementia diagnosis poses multiple challenges, but through research we will be able to improve diagnosis and ultimately find treatments that tackle the specific causes of the condition."
He added: "Anyone who is concerned about changes in their behaviour should speak to their GP."