Dementia and Cancer – Are they linked?
A look at the intriguing relationship between cancer and dementia. Are they linked? And how?
Dementia illnesses such as Alzheimer’s disease are brain disorders that cause the progressive degeneration of neurons and result in the loss of memory and cognitive skills. Like cancer, dementia is a chronic condition, which tends to occur more frequently later in life, and is one of the most common health problems among people over the age of 65.
The two conditions also share many lifestyle-related risk factors, including physical inactivity, poor diet, excessive alcohol consumption and smoking.
However, it has long been suggested that, despite these similarities, there may be an inverse association between dementia and cancer, meaning that having one protects against the other.
This has been found, for example, in a study published in the Journal of Alzheimer’s Disease by Dr. Steven Arnold, of Harvard Medical School, Massachusetts, and a team of colleagues.
The researchers analysed data from participants in two studies that had been previously conducted to understand the link between ageing and Alzheimer’s disease (AD). They focussed on participants with or without a history of cancer and compared their risk of developing the brain condition.
They found that those who had a history of cancer had significantly lower odds of AD than those without. The association remained significant even when the researchers eliminated from their analysis other factors known to cause Alzheimer’s disease, like age, sex, race, education, and certain genetic mutations. And not only that. The autopsy of deceased participants showed that those with a history of cancer had significantly fewer neurofibrillary tangles in the brain – one of the hallmarks of Alzheimer’s disease.
Interestingly, the results of earlier research, this time conducted by a team of the Geriatric Research Education and Clinical Center and Boston VA Medical Center, in Boston, Massachusetts, suggest that the opposite is also true.
Not only did the researchers find that cancer survivors they followed up for an average of 10 years had a 33 per cent reduced risk of developing Alzheimer’s disease, compared with people without cancer, but also that having dementia of any type lowered the risk of subsequent cancer by 56 per cent.
Similar findings have been reported for other age-related degenerative disorders, most notably Parkinson’s disease and Huntingdon disease.
The exact reason for the inverse association between cancer and certain brain conditions is not known.
But an important implication of the results published to date is that, as scientists will be able to gain an understanding of the underlying biology of the link between cancer and neurodegeneration, they will open up important new avenues of treatment for patients with either disease.