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Wolfson Institute of Population Health

Late-life depression could be an early indicator of dementia

A new WIPH study shows that, while having depression is known to increase the risk of developing dementia, depression is also an early indicator of dementia, particularly in older people.

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This research found that people with depression were more likely to develop dementia than those without, but the chance of someone experiencing depression increased steadily in the ten years leading up to a dementia diagnosis. If depression were causing dementia, it would be expected that those who have experienced depression for longer would be at greater risk. In this study, the reverse was shown to be true:  the link between depression and dementia became stronger just before the time of dementia diagnosis. The finding suggests that the onset of depression later in life should be viewed as a possible early indicator of dementia, which may help to improve early diagnosis of the disease. 

Researchers analysed the health records of nearly 500,000 participants from the UK Biobank, comparing those with and without diagnoses of both depression and dementia. They performed a series of analyses to establish whether depression was likely to be causing dementia or whether early dementia was likely to be causing depression, including using MRI brain scans of over 41,000 Biobank participants to examine whether the pattern of changes in the brain associated with depression was different in older than younger adults with depression. 

Results showed that the link between dementia and depression was highly specific. When researchers adjusted for other variables that could affect the link between depression and dementia (eg: poverty, gender, education, smoking, and social isolation) they still found that depression roughly doubled the risk of developing dementia. The data also showed that more severe depression was associated with greater dementia risk. 

In people aged 65 and older, depression was associated with changes in brain regions linked to Alzheimer's disease, particularly the hippocampus. These changes in brain structure suggest that depression in older adults might reflect early Alzheimer’s disease changes in the brain. However, younger people with depression did not show the same patterns of brain change, suggesting that depression may affect brain health differently at different ages. 

Professor Charles Marshall, who led the study, said: “Depression is often viewed as a ‘modifiable’ risk factor for dementia, but this may need to be re-evaluated in light of our study. We hope that the findings will lead to a more nuanced approach when considering whether treating depression could be a way of preventing dementia. Our results suggest that while treating depression earlier in life might have a small benefit on brain health, there may be more to be gained from using depression in later life as a way of identifying people who are in the early stages of dementia. An awareness of this could help to improve access to timely diagnosis and treatment of dementia.” 

 

Depression and dementia: interrogating the causality of the relationship. Alvar Paris, Guru Amirthalingam, Tasvee Karania, Isabelle F Foote, Ruth Dobson, Alastair J Noyce, Charles R Marshall, Sheena Waters. Journal of Neurology, Neurosurgery and Psychiatry. 11 January 2025. DOI: 10.1136/jnnp-2024-334675

  

 

 

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