Findings from a large Korean study suggests that radiation therapy may reduce by up to 23% the risk of dementia for some cancer survivors, compared with those who had not undergone treatment, reports Fox News.
In the study, led by the Seoul National University College of Medicine and published in JAMA Network Open, data from more than 70 000 breast cancer survivors were compared with a cancer-free control group for an average of 7.3 years.
The study was adjusted for other factors that could have contributed to Alzheimer’s risk, including age, income levels, geographic location, body mass index, comorbidities (diabetes, hypertension, high cholesterol and chronic kidney disease) and health-related behaviours (smoking, alcohol consumption and physical activity).
This outcome conflicts with previous concerns about breast cancer patients experiencing cognitive decline after treatment.
Chemotherapy has previously been linked to a condition called “chemo brain”, where patients experience cognitive decline.
“Chemo brain refers to cognitive dysfunction, including thinking and memory problems, that occur in patients with cancer during and after chemotherapy,” the researchers wrote.
This is different from Alzheimer’s, however – with "chemo brain”, the cognitive impairment is described as “subtle” and doesn’t keep the patient from retrieving remote memories.
“Concerns about chemo brain and the long-term adverse effects of breast cancer treatment on cognition are common, but our findings suggest that this treatment does not directly lead to AD,” the researchers noted.
Overall, the breast cancer survivors, particularly those who were 65 and older, showed an 8% lower risk of dementia within the five years of treatment.
Those who received radiation showed the most risk reduction, the researchers found.
In fact, they wrote, some studies have shown that certain drugs given to breast cancer patients can help to reduce the formation of amyloid-beta and tau proteins in the brain, one of the hallmarks of Alzheimer’s.
Based on the findings, the researchers recommend that breast cancer patients take steps to reduce modifiable risk factors for Alzheimer’s, such as smoking and diabetes, along with receiving standard cancer treatment.
Limitations
The team acknowledged some limitations to the study.
Information about patients’ breast cancer stage and radiation dose was not available, and it also possible that the number of Alzheimer’s diagnoses was underestimated, they noted.
Also, because the study focused on patients with “operable” breast cancer, it may not represent the risk of Alzheimer’s among elderly patients, those with “critical comorbidities” or patients with advanced-stage disease, they said.
“We could not evaluate the long-term increase in AD risk because our follow-up period was relatively short (maximum, 11 years),” they wrote.
“Additional studies with long-term observation periods are warranted to examine long-term associations between AD risk and breast cancer survival duration.”
Maria Carrillo, PhD, the Alzheimer’s Association chief science officer and medical affairs lead in Chicago, who was not involved in this most recent study, said this topic has been explored in previous studies.
“There have been many published reports from observational studies of cancer survivors with decreased risk of Alzheimer’s disease, but also some that found increased risk,” she said, cautioning against drawing “abrupt conclusions” based on this study.
“Previous research on cancer survival and treatment and Alzheimer’s risk, much of it cited by the authors of this article, has produced mixed – even contradictory – results,” she added.
“More research is needed, especially longer studies in more representative study populations.”
The most interesting aspect of this study, Carrillo said, was the finding that radiation therapy was associated with a 23% Alzheimer’s risk reduction, while other cancer treatments showed no risk reduction.
This could be due to radiation’s capability to lower inflammation levels, the expert suggested.
“Lowering inflammation in the body and brain can reduce amyloid beta or slow amyloid beta production, delaying the onset of symptomatic Alzheimer’s,” she said. "More research is needed to see if this is, in fact, the case.”
Around 7.2m Americans aged 65 and older have Alzheimer’s, according to the Alzheimer's Association.
Study details
Alzheimer Disease in Breast Cancer Survivors
Su-Min Jeong, Wonyoung Jung, Hyeonjin Cho, et al.
Published in JAMA Network Open on 20 June 2025
Key Points
Question
Is breast cancer survivorship associated with the risk of Alzheimer dementia (AD), and how are cancer treatments associated with this risk?
Findings
In this cohort study of 70 701 breast cancer survivors matched 1:3 with cancer-free controls, breast cancer survivors demonstrated a lower risk of AD compared with controls, particularly among those 65 years or older, although the lower risk did not persist beyond five years. Treatment with radiation therapy was associated with reduced AD risk.
Meaning
Breast cancer survivors may have a slightly lower risk of AD compared with cancer-free individuals, potentially influenced by cancer treatments, underscoring the need for further research on long-term neurocognitive outcomes in this population.
Abstract
Importance
Cancer-related cognitive impairment is a common concern after breast cancer treatment. However, the association between breast cancer survivorship and the risk of Alzheimer dementia (AD) remains unclear.
Objective
To evaluate the risk of AD among breast cancer survivors compared with cancer-free controls and examine the potential association of cancer treatments with AD risk.
Design, Setting, and Participants
This retrospective cohort study used data from the Korean National Health Insurance Service. A total of 70 701 patients who underwent breast cancer surgery between January 1, 2010, and December 31, 2016, were included and matched with cancer-free controls (1:3). Participants were followed up for a median (IQR) of 7.3 (5.7-9.0) years. Data analysis was performed from January 2024 to June 2024.
Exposures
Breast cancer diagnosis, surgery, and subsequent treatments, including anthracycline chemotherapy and radiation therapy.
Main Outcomes and Measures
The primary outcome was the incidence of AD. Subdistribution hazard ratios (SHRs) and 95% CIs were calculated using competing risk regression models, adjusting for sociodemographic factors and comorbidities.
Results
Among 70 701 breast cancer survivors (mean [SD] age, 53.1 [8.5] years), 1229 cases of AD were detected, with an incidence rate of 2.45 per 1000 person-years. Survivors exhibited a slightly lower risk of AD compared with cancer-free controls (SHR, 0.92; 95% CI, 0.86-0.98), especially among individuals 65 years or older (SHR, 0.92; 95% CI, 0.85-0.99). However, landmark analyses found that this lower risk did not persist beyond 5 years of survival. Cancer treatment with radiation therapy (adjusted HR, 0.77; 95% CI, 0.68-0.87) was associated with reduced risk of AD among survivors.
Conclusions and Relevance
This cohort study of breast cancer survivors found a lower risk of AD compared with cancer-free controls, despite common concerns about cognitive decline after treatment. The findings suggest certain cancer treatments potentially have benefits for lower AD risk. Further research is needed to assess the long-term risk of AD in this population.
JAMA article – Alzheimer Disease in Breast Cancer Survivors (Open access)
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