Cancer raises mental dysfunction risk

A recent study suggests that cancer is associated with cognitive impairment in long term. Previous reports have identified short-term mental deficits in cancer survivors, but it was unclear if these difficulties persist or change over time. Researchers from the University of Southern California at Los Angeles assessed long-term cognitive function in 702 cancer survivors and in their cancer-free twins. The subjects were 65 years of age or older and had survived cancer for 5 years or longer. Cancer survivors were at least twice as likely to have cognitive dysfunction as compared to their twins. The risk of dementia was also increased among the survivors, but this did not reach statistical significance. Still, everyone does not believe that the results are sound enough to conclude that cancer increases the risk of long-term mental difficulties. Editorialists from the M. D. Anderson Cancer Center in Houston after a thorough diagnostic workup, in a related editorial noted that researchers did not demonstrate a preponderance of dementia in co-twins with a history of cancer. The editorialists add that problems with the design of the study, including their use of a poor measure of cognitive function, cross-sectional design, and failure to adequately rule out competing causes of suspected cognitive dysfunction, diminish confidence in their interpretation that cancer survivors demonstrated an increased risk of cognitive dysfunction than cancer-free co-twins.