Alzheimer’s Disease May Protect Against Cancer and Vice Versa

As we get older, and care for our parents as they get older, the most feared age-related conditions we face are arguably Alzheimer’s disease and cancer. But researchers at Washington University have just shown that at least we don’t have to fear both of them at the same time; they recently published a paper in the medical journal of the American Academy of Neurology demonstrating that people with Alzheimer’s disease have a significantly reduced risk of being hospitalized for cancer [1].

Feared age-related conditions

This potential link between these two diseases had been noted for some time, but in this study researchers devoted considerable effort to overcoming the limitations in their previous work. Firstly, they used a population-based sample of 3,020 people older than 65, so their results were not limited to a particular geographic area or socio-economic segment of society. Secondly, they used hospital records rather than informant reports to quantify cancer diagnoses. This controlled for the risk that people with Alzheimer’s disease may be less likely to report their cancers than those without. And lastly, to ensure that they were not seeing less cancer in Alzheimer’s patients because physicians were less likely to look for cancer in people with dementia, or because people with dementia simply die earlier than those without it and thereby avoid cancer, they also looked at cancer risk among people with vascular dementia. Vascular dementia is not neurodegenerative in origin; rather, it results from brain damage due to vascular pathology.

Neurodegenerative Disease and the Coming Epidemic

At Neuroscience 2008, the 38th annual meeting of the Society for Neuroscience held last month in Washington D.C., a number of researchers presented evidence that a small, soluble, clustered form of a protein called amyloid beta may be responsible for brain damage in Alzheimer’s disease patients [1]. In addition, scientists report that they are finding new sources and uses of neural stem cells that may replace cells damaged by neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease [2].

Creative Commons License photo credit: neurollero

Why are these reports significant? Because until recently, large insoluble amyloid beta plaques, or deposits, were considered the likely cause of Alzheimer’s disease. The plaques were thought to disrupt brain cell communication. However, new findings show that an early (i.e. small), soluble, clustered form of amyloid beta called protofibrils is found in high levels in the brains of people with Alzheimer’s disease [1]. Researchers also found a strong correlation between the presence of high levels of protofibrils in the brains of transgenic mouse models of Alzheimer’s disease and the cognitive impairments associated with the disease.