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Effects of chemotherapy on cognitive function
Although cancer patients have been receiving chemotherapy for over five decades, it has been only recently that patients have reported difficulties in cognitive function from chemotherapy. Several reviews on chemotherapy-induced impairments in cognitive function have been published in recent years. However, findings have been inconsistent and, as yet, relatively little is known about the effects of chemotherapy on cognitive function. In this manuscript we report our meta-analysis, performed to determine the effect of chemotherapy on the various domains of cognitive function. Sixteen studies published between 1980 and June 2004 had sufficient data to be included in the meta-analysis. Seventy-five percent of the studies were cross-sectional and 25% were longitudinal. Twenty-four percent of studies included patients were currently receiving chemotherapy. In the remainder of the studies, the time since treatment was < 1 year (20%), 1-2 years (31%), 2-5 years (14%), > 5 years (11%). A total of 224 effect sizes were calculated for tests results. All averaged, weighted effect sizes across various domains of cognitive function were in the negative direction, indicating that mean scores on neuropsychological tests for chemotherapy patients were on average lower than comparison scores. However, most deficits in this study ranged from small to moderate and were non-significant. Only one domain of cognitive function, visual memory, had a significant effect for chemotherapy-induced impairment across all comparison types. While differences were found based on the type of comparison, given the limited number of studies and the heterogeneity of diagnoses, types of chemotherapy given, and length of time since treatment, these results need to be interpreted with caution. More studies are needed to further elucidate the phenomenon of chemotherapy-induced cognitive impairments. While the chemotherapy does appear to have a negative impact on cognitive function, it is not clear how clinically significant the impairments in cognition are to an individual’s everyday functioning. Reference: Catherine Jansen Kaiser Permanente Medical Center, San Francisco, California
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