The upside to memory decline? Lower risk of cancer death

A new study is adding further evidence to the idea that there is an inverse relationship between dementia and cancer.

The research, published in the journal Neurology, shows that older people who have memory and thinking problems, but have not been diagnosed with dementia, have a lower risk of dying from cancer.

Past studies have shown that people with Alzheimer's disease are half as likely to develop cancer, however, the reasons for this relationship are not entirely clear.

"One possibility is that cancer is underdiagnosed in people with dementia, possibly because they are less likely to mention their symptoms or caregivers and doctors are focused on the problems caused by dementia. The current study helps us discount that theory," explains study author Dr. Julián Benito-León from University Hospital in Spain.

The study looked at 2,627 Spanish seniors aged 65 and older and tracked them for almost 13 years. Researchers tested the participants' memory and thinking skills at the start of the study and again three years later.

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The participants were divided into three groups: those whose memory and thinking scores declined the fastest, those whose scores improved, and those in the middle range.

The results show that those in the fastest declining group were 30 per cent less likely to die of cancer after factoring in smoking, diabetes, heart disease and other risk factors.

Because the participants' health was tracked over the long-term, it is unlikely the aforementioned reasons explain the connection between dementia and cancer.

Researchers believe it may have more to do with cell development and aging.

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The New Scientist explains that "as we get older, many of the body's cells undergo senescence – a process that stops them dividing and triggers the release of inflammatory proteins."

While this process is believed to protect us from cancer, senescence may also be linked to neurodegenerative diseases, such as Alzheimer's.

"We need to understand better the relationship between a disease that causes abnormal cell death (dementia) and one that causes abnormal cell growth (cancer)," Benito-León concludes. "With the increasing number of people with both dementia and cancer, understanding this association could help us better understand and treat both diseases."

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