1) First you have cancer. Saving your bacon requires a heavy dose of chemo. 2) The chemotherapy drugs generate diffuse, destructive physical changes in your brain. Memory and other cognitive abilities are affected. 3) Your mental decline, in aging, is now on a faster track, and you have now roughly doubled risk for the onset of senility.

I attended a scientific meeting over the weekend, and had a discussion with a long-time collaborator and friend, Paula Tallal (a professor and neuroscience institute director at Rutgers University), about “chemobrain”, and about the very similar cognitive losses that result from chronic, low-grade brain infections. The subject came up because both of us have people close to us who had suffered cognitive losses following these common conditions. After all, about a third of we Americans develop and are treated for cancer in our lifetimes, and millions of us suffer other assaults that result in low-grade, diffuse damage to the brain. These can arise as a consequence of a variety of other medical treatments, from traumatic injuries, from chronic low-grade infections, and from environmental poisons. In every case, diffuse brain damage results in losses in cognitive abilities (memory, mental agility). Examples:

Chemo-brain” arising from cancer and subsequent chemotherapy. There is evidence that the more aggressive the chemotherapy (reflecting the aggressiveness of the cancer itself), the more serious the neurological impacts. (Who said life was fair.)

Cognitive losses arising from bypass and open heart surgery, presumably due to an extended epoch of abnormal brain oxygenation.

Cognitive losses arising from chemical pollutants. You just don’t want to live near a mercury or cadmium mine, or eat too many fish from the Great Lakes (or fish from lots of other favorite fishing holes).

Traumatic brain injury arising from concussions, or from more severe injuries.

Chronic Lymes Disease (if the initial treatment doesn’t kill it, a low-grade brain infection that is almost impossible to block can be set in motion).

HIV infection. We all know that AIDS treatments have dramatically improved. At the same time, millions of treated individuals still suffer from low-grade chronic infections that slowly, inexorably degrade brain function.

Paula reminded me of a Gold-Standard scientific study on this subject, published in the Journal of the National Cancer Institute in 2005. (Heflin LH, et alia, J Natl Cancer Inst 97:854). [ www.pubmed.gov ; type in Heflin LH + cancer + cognitive deficits] This study is special because it uses an analysis of cognitive ability and senility in identical twins. By this strategy, inherited and childhood rearing factors are ruled out from contributing to measured differences.
The results: You’ve had cancer. You’re twice as likely to be significantly cognitively impaired. You’re twice as likely to be senile.
Like I said, a triple whammy.

ONE MORE POINT:
People argue about whether or not Alzheimer’s incidences are on the rise. How can they NOT be, when many factors that affect the probability and the timing of AD onset are products of modern societies? Maybe that contributes to the explanation as to why it took Alois Alzheimer about 7 years to identify the handful of patients with the condition that bears this name!