Study links mental disorders early in life to dementia

Anna Samecki

18/02/2022 2:41:49 PM

Mental health disorders are often an underappreciated category of modifiable risk factors for dementia, new research suggests.

Older man looking stressed
Links between the risk of early-life mental disorders and dementia are stronger than for physical diseases, and on par with the strongest risk factor gene for Alzheimer’s disease.

Almost half a million Australians are currently living with dementia.
By 2056, it is expected that number will increase to over one million.
Dementia is currently the second leading cause of death for Australians, and the leading cause of death for women.
Prevention advice often includes recommendations around modifiable risk factors such as diet, exercise, alcohol consumption, hypertension, diabetes and cholesterol.
But according to researchers, mental disorders are often an underappreciated category of modifiable risk factors for dementia.
In a recently published large longitudinal study, which looked at the health data of a third of New Zealand’s population over 30 years, researchers found that people with early-life mental disorders were at elevated risk of dementia, including Alzheimer’s disease.
The study looked at a broad range of mental disorders, including substance use, psychotic disorders, mood disorders, neurotic disorders, personality disorders, developmental and behavioural disorders, as well as self-harm.
The increased risk was stronger for mental disorders than physical diseases, and on par with the strongest risk factor gene for Alzheimer’s disease, the APOE4 allele.
The study also found that among individuals with dementia, those with a mental disorder developed dementia a mean 5.6 years earlier than those without a mental disorder.
The authors state their findings are significant in light of many dementia indexes excluding mental disorders, and only depression making an appearance among the top 12 preventable risk factors most strongly associated with dementia.
‘Associations were observed across different mental disorders, suggesting that preventing any disorder in early life might benefit later-life cognitive health,’ the authors write.
However, they also acknowledge that associations are not evidence of a causal link.
‘Mental disorders may be indicators of risk rather than causes of dementia,’ they say.
‘We established the temporal ordering of mental disorders before dementia, addressed reverse causation, and ruled out poor physical health and socioeconomic deprivation as alternative explanations for associations.
‘However, there may be shared risk factors we did not measure that underlie the association between mental disorders and dementia, including a general liability to poor brain health.’
The researchers conclude that even if mental disorders do not cause dementia, they are a very early warning sign of subsequent cognitive decline with intervention implications.
Aged care GP Dr Sachin Patel told newsGP that while more research is needed to further explore the links between mental health and dementia, he isn’t surprised by the findings.
‘There is a two-way link between mental health and chronic disease,’ he said.
‘People with mental health conditions are more vulnerable to chronic disease, and people with chronic disease are more vulnerable to mental health conditions.’
Dr Patel believes the findings serve as a reminder to be cognisant of mental health conditions, and their potential impact on future health, when performing preventive health activities.
‘Mental health in general needs to be addressed when considering dementia and giving preventive advice,’ he said.
‘There is probably a need for more research [in this space], but it is not going to harm us to be more in tune with people’s mental health needs when it comes to preventing chronic disease.’
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