Older adults with incident cancer had higher memory function and slower memory decline before and after their diagnosis than similarly aged individuals who remained cancer free, a study published in JAMA Network Open showed.
These findings suggest that a common pathologic process in cancer and Alzheimer’s disease (AD) may work in opposite directions, according to the researchers.
Prior research has reported lower incidence of Alzheimer disease among people with a history of cancer compared with cancer-free population controls; however, evidence remains scarce on the long-term cognitive trajectories of these two populations, Monica Ospina-Romero, MD, from the department of epidemiology and biostatistics at University of California, San Francisco, and colleagues wrote.
“We started this research because the inverse association between cancer and Alzheimer's and dementia is such a mystery,” Maria Glymour, ScD, MS, from UCSF, told Healio Psychiatry. “We hope that by researching this, we can identify a biological mechanism that could be used to help prevent Alzheimer's disease.”
To compare the long-term memory trajectories before and after incident cancer diagnoses (excluding nonmelanoma skin cancer) with those of similarly aged individuals without cancer, researchers conducted a population-based cohort study of U.S. adults from the Health and Retirement Study.
They assessed participants every other year for up to 16 years from 1998 to 2014 to determine composite memory score and compare the rate of memory change among those diagnosed with cancer during follow-up before and after diagnosis with the rate of memory change in cancer-free individuals using linear mixed-effect models with random intercepts and slopes.
Of 14,583 participants included in the study (mean age = 66.4 years; 58% female), 2,250 had a cancer diagnosis and 12,333 had no cancer diagnosis during follow-up (mean 11.5 years).
In the decade before cancer diagnosis, Ospina-Romero and colleagues observed a slower rate of memory decline (10.5%; 95% CI, 6.2-14.9) than that of similarly aged cancer-free participants. In addition, a new cancer diagnosis was linked to a short-term decrease in memory (–0.058 SD units; 95% CI, –0.084 to –0.032) compared with memory prior to diagnosis.
“Although there was a short-term memory decline after the diagnosis of cancer, it was small and overall rate of memory change associated with aging was not increased after a diagnosis of cancer,” Glymour said. “This may be reassuring to people recently diagnosed with cancer.”
Analysis revealed that average memory function immediately before cancer diagnosis was 0.096 SD units higher (95% CI, 0.06- 0.133) for individuals diagnosed at age 75 years than memory function among cancer-free adults of the same age. The results also showed a 3.9% (95% CI, 0.9-6.9) slower rate of memory decline after a cancer diagnosis compared with individuals without cancer.
“These novel findings support the possibility of a common pathologic process working in opposite directions in cancer and AD,” the researchers wrote in the full study. “Identification of a potential association between and neurodegeneration may open a new avenue in research for prevention and treatment of AD.”
An important question for future research is why individuals who have had cancer or develop cancer perform better on memory testing than those who stay cancer free, Olivia I. Okereke, MD, SM, from Massachusetts General Hospital, and Mary-Ellen Meadows, PhD, from Brigham and Women’s Hospital and Dana-Farber Cancer Institute, posed in an invited commentary. – by Savannah Demko
Disclosures: Glymour and another author report grants from the National Institute on Aging; no other authors report relevant financial disclosures. Okereke and Meadows report no relevant financial disclosures.