Persistently engaging in negative thinking patterns may raise the risk of Alzheimer's disease, finds a new study published in Alzheimer's & Dementia. The study by University College London (UCL), among people aged over 55, has proved that repetitive negative thinking (RNT) is linked to subsequent cognitive decline as well as the deposition of harmful brain proteins linked to Alzheimer's.
Lead author Dr Natalie Marchant (UCL Psychiatry) said: "Depression and anxiety in mid-life and old age are already known to be risk factors for dementia. Here, we found that certain thinking patterns implicated in depression and anxiety could be an underlying reason why people with those disorders are more likely to develop dementia.
"Taken alongside other studies, which link depression and anxiety with dementia risk, we expect that chronic negative thinking patterns over a long period of time could increase the risk of dementia. We do not think the evidence suggests that short-term setbacks would increase one's risk of dementia.
"We hope that our findings could be used to develop strategies to lower people's risk of dementia by helping them to reduce their negative thinking patterns."
For the Alzheimer's Society-supported study, the research team from UCL, INSERM and McGill University studied 292 people over the age of 55 who were part of the PREVENT-AD cohort study, and a further 68 people from the IMAP+ cohort.
Their cognitive function was assessed, measuring memory, attention, spatial cognition, and language. Some (113) of the participants also underwent PET brain scans, measuring deposits of tau and amyloid, two proteins which cause the most common type of dementia, Alzheimer's disease, when they build up in the brain.
The researchers found that people who exhibited higher RNT patterns experienced more cognitive decline over a four-year period, and declines in memory (which is among the earlier signs of Alzheimer's disease), and they were more likely to have amyloid and tau deposits in their brain.
Depression and anxiety were associated with subsequent cognitive decline but not with either amyloid or tau deposition, suggesting that RNT could be the main reason why depression and anxiety contribute to Alzheimer's disease risk.
"We propose that repetitive negative thinking may be a new risk factor for dementia as it could contribute to dementia in a unique way," said Dr Marchant.
The researchers suggest that RNT may contribute to Alzheimer's risk via its impact on indicators of stress such as high blood pressure, as other studies have found that physiological stress can contribute to amyloid and tau deposition.
Co-author Dr Gael Chételat (INSERM and Université de Caen-Normandie) commented: "Our thoughts can have a biological impact on our physical health, which might be positive or negative. Mental training practices such as meditation might help promoting positive- while down-regulating negative-associated mental schemes.”
"Mental health could be a vital cog in the prevention and treatment of dementia; more research will tell us to what extent," said Fiona Carragher, Director of Research and Influencing at Alzheimer's Society,
The researchers say RNT should now be further investigated as a potential risk factor for dementia, and psychological tools, such as mindfulness or meditation, should be studied to see if these could reduce dementia risk.
