Alzheimer Disease in Breast Cancer Survivors.

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.