The prevalence of CRCD in studies of mostly involving patients with breast cancer is between 17% and 75%. We found that CRCD was reported by 14% of participants who had cancer and by 8% of those who did not. The lower prevalence of self-reported memory problems in our study probably reflects the fact that our analysis included a greater variety of cancer types (every cancer except brain tumors) and was likely based on variable times since diagnosis and treatment. That a history of cancer was associated with a 40% higher rate of self-reported memory problems underscores the potential public health importance of this understudied problem.
We found a positive association between age and reported memory problems (), as expected, given the literature on this topic when we examined the entire sample. However, examination of the cancer subsample revealed a relationship between cancer history and memory for younger persons but not older persons. Specifically, memory problems were greater among participants younger than 55 years of age. This finding could be the result of many factors. First, the sample included substantially more individuals who had not had cancer. Thus, the expected relationship between older age and memory problems was confirmed. However, in the cancer sample, memory problems were inversely associated with age. The observed findings could also be the result of several differences between younger and older participants. For example, younger participants in the sample could be involved in work or other social environments and interactions in which cognitive dysfunction, especially declining memory, is much more noticeable than in older participants. The observed age difference could also be the result of a greater willingness of younger patients to report memory problems. Differences in treatment (chemotherapy dosage, radiation exposure) may also affect the rate of reported CRCD; however, with the present data, we could not examine this relationship. Additional studies could use well-calibrated cognitive performance tests to help determine whether younger patients with cancer simply notice the memory problem more because they have higher baseline memory abilities than do older patients with cancer, or because the older individuals have a higher expectation that they will have memory difficulties and so do not label memory deficits as problems to the same degree as younger individuals who do not have this same expectation.
Although not yet tested, it is possible that participants with CRCD might not be willing or able to participate in clinical cancer research. Neurocognitive dysfunction is a potentially debilitating adverse effect of cancer and its treatments. Cognitive impairment has a negative effect on clinical decision making among patients with cancer,20–22
and severe cognitive impairment has been reported in decisions to decline life-prolonging therapy and nonadherence to medication recommendations among women with early-stage breast cancer undergoing hormonal therapy.23
In this cross-sectional study, we could not determine to what extent memory problems changed over time or which cancer stages and treatments might contribute to self-reported memory problems. We also could not exclude the potential of unmeasured confounding effects from other factors. We did not assess the degree of impairment, which would be necessary to ascertain the full implications of the problem. Although participants were screened with the question, “What kind of cancer?” to identify those with brain tumors, the data did not support reliable analysis by cancer type. We did not assess whether time from diagnosis, cancer type, or both affects memory because we did not have data on the specific time of diagnosis and because cancer type could not be verified. In addition, such analyses are likely to be biased by survival effects. Longer time since diagnosis could be confounded by cancer stage and type. For example, participants with late-stage disease or deadly cancers, such as lung and pancreatic cancers, may not have been well enough to be included in the sample. Additionally, the present study assessed memory problems by patient self-reported questionnaire instead of objective neuropsychologic measures. However, to date, there are no gold-standard measures of CRCD. Albeit subjective and possibly lacking psychometric rigor, patient self-reported complaints of CRCD could well precede clinical findings of neurocognitive impairments. Additional studies are needed that more systematically control for plausible alternative explications of CRCD (eg, use of medication), evaluate broader domains of cognitive function (eg, attention, memory, processing speed, and executive function) that could be affected by cancer and cancer treatments (eg, chemotherapy, radiotherapy), and more reliably estimate the prevalence of these debilitating adverse effects.
The prevalence of self-reported CRCD in a large, nationally representative sample of the US population was 14%. Participants with a history of cancer had a 40% greater likelihood of having memory problems than those without a history of cancer. Our findings showed a positive relationship between age and self-reported memory problems for the entire sample. However, a subsample examination showed the effect of age, particularly among younger participants. Specifically, self-reported memory problems were greater among participants younger than 55 years of age. Socioeconomic and racial/ethnic status can affect cancer treatment and its outcomes. However, our analysis revealed that the effects of cancer on CRCD remain after controlling for these variables. These findings call to attention the need to more systematically assess and treat CRCD in patients with cancer and cancer survivors.