SAN FRANCISCO ― Although cancer patients frequently experience short-term cognitive deficits, little is known about how long these deficits last or whether they worsen over time. Now, data from a large national sample suggest that cognitive deficits may persist long term.
When compared with matched individuals who were without cancer, long-term cancer survivors performed worse on a test of processing speed, attention, and learning and working memory involving executive functions domains. Cancer survivors also more frequently problems with memory and confusion, even after adjusting for confounders, such as age and education level.
These effects appeared to be greater in long-term vs short-term cancer survivors, but age seemed to be a factor. Cancer survivors aged 60 to 75 years had worse performance on the cognition test as compared with those older than 75 years.
The study was presented during a poster session at the Cancer Survivorship Symposium (CSS) Advancing Care and Research.
"A lot of the recent literature on cognitive dysfunction has been conducted in breast cancer patients, and we wanted to expand upon that and look at different cancer types," said lead author Annalynn Williams, a doctoral candidate in epidemiology at the University of Rochester, in New York. "In this group, cognitive testing was done in those aged 60 and above, and they were long-term survivors who were on average 12 years since their diagnosis.
"We hypothesized that in this nationally representative sample, the survivors would be more susceptible to cognitive impairment, and we found that was true," she told Medscape Medical News. "What was interesting was that those younger than 75 performed worse than cancer survivors above the age of 75."
This may be because of what is known as the phase-shift hypothesis, in which the trajectory of cognitive impairment is thought to parallel that of normal aging, she suggested.
"That suggests that we've shifted the trajectory of their cognitive decline at the time of diagnosis and treatment, and then they continue to progress at a normal rate, similar to the rest of the population," she explained. "And our data support this, because in the younger group, we see more impairment than in the older group, which might have just caught up to the rate in the rest of the population."
Cognitive Function Decreased
Using data from the National Health and Nutrition Examination Survey from 1999 through 2002, Williams and her colleagues identified 408 cancer survivors and 2639 participants who did not have cancer. All participants were aged 60 years or older. The average age of the cancer survivors was 72.8 years old; the median amount of time after diagnosis was 11.5 years.
In both of these cohorts, cognitive function was assessed on the basis of self-reported problems with memory or confusion and on results on the Digit Symbol Substitution Test (DSST), a test of processing speed, attention, and learning and working memory involving executive functions domains.
After adjustment for covariates, cancer survivors scored, on average, 1.99 points lower on the DSST as compared with control participants (ß=-1.99; 95% confidence interval [CI], -3.94 to - 0.05).
Cancer survivors also had 17% higher odds of self-reporting problems with memory or confusion (odds ratio [OR], 1.17; 95% CI, 0.89 - 1.53).
Long-term survivors (≥5 years) performed worse on the DSST (ß = -2.38) and had higher odds of self-reported problems with memory and confusion (OR, 1.41) compared with control participants.
Short-term survivors also performed worse on the DSST (ß = 1.18) but had fewer self-reported problems (OR, 0.65).
The results suggested that age modifies the association between cancer diagnosis and DSST score (P = .11), insofar as a larger effect was observed in the younger group (those aged 60 to 75 years). Among those younger than 75, cancer survivors performed 3.25 points lower on the DSST compared with control persons (ß = -3.25).
However, this difference was only 0.18 points lower among those aged 75 or older (ß =-0.18).
"I think this is good, having information across all types of cancer, which adds more information to the literature," said Williams. "What we are seeing is that 12 years later, cancer survivors are still performing worse than the rest of the population."
PULL QUOTE “Twelve years later, cancer survivors are still performing worse than the rest of the population.”
Mindful of Impact on Cognition
Commenting on the study, Merry Jennifer Markham, MD, FACP, associate professor in the Division of Hematology and Oncology at the University of Florida, in Gainesville, noted that it is well documented that cancer treatment is associated with short-term cognitive changes.
"This study highlights that certain types of cognitive changes in older cancer survivors may be persistent once therapy ends," she said. "In this study, survivors aged 60 to 75 seemed to have more of a detrimental score on cognitive testing when compared to participants without cancer than did survivors older than 75."
Although it is too soon to understand how this information will affect current therapeutic approaches to older patients, Dr Markham said: "Clearly, we should be mindful of the impact of our treatments on cognition in patients of all ages, including the advanced age population."
The authors and Dr Markham have disclosed no relevant financial relationships.
Cancer Survivorship Symposium (CSS) Advancing Care and Research: Abstract 193. Presented January 16, 2016.
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Cite this: Cognitive Deficits Continue Long Term in Cancer Survivors - Medscape - Jan 19, 2016.