Hormonal Therapy for Breast Cancer May Lower Dementia Risk in Older Women

Women ages 65 and older who took hormonal therapy for breast cancer for several years had a lower risk of developing Alzheimer’s disease and other types of dementia than women with breast cancer who didn’t take hormonal therapy, according to a study in JAMA Network Open. 

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  Overall, women who took hormonal therapy had a 7% lower risk of dementia than women who didn’t take hormonal therapy.

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  Women ages 65 to 74 who identified as Black had a 24% lower risk of dementia; white women in the same age group had an 11% lower risk.

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  The protective benefits of hormonal therapy against dementia began to fade away by age 75 in white women, but remained in Black women age 75 and older.

Although the protective effects of hormonal therapy against dementia decreased with age, it’s reassuring to know that there were some benefits. 

“The benefits of [hormonal therapy] decreased for women aged 75 and older, particularly in those who identified as white. This suggests that the timing of [hormonal therapy] initiation is crucial and treatment plans should be tailored to a patient’s age,” lead author Chao Cai, assistant professor at the University of South Carolina College of Pharmacy, said in a statement.

Hormonal therapy (also called anti-estrogen therapy) is used to prevent the risk of hormone receptor-positive breast cancer from coming back. While hormonal therapy is known to have benefits for people with this type of breast cancer, researchers have questioned whether hormonal therapy might increase the risk of Alzheimer’s disease and other dementias.

For this study, the researchers compared the risk of dementia in women who had taken hormonal therapy for breast cancer with those who hadn’t taken hormonal therapy. They used information from the SEER-Medicare database to identify the records of 18,808 women ages 65 and older (88% white, 7% Black) who were diagnosed with breast cancer between 2007 and 2009. About 66% of the women in the study started taking hormonal therapy within three years of being diagnosed with breast cancer; 34% didn’t take hormonal therapy. The researchers tracked the two groups of women for at least 10 years.

More than 75% of the women in the hormonal therapy group took an aromatase inhibitor and about 24% took tamoxifen. The women took hormonal therapy for an average of two years. 

During 12 years of follow-up, 24% of women who took hormonal therapy and 30% of women who didn’t take hormonal therapy were diagnosed with dementia. The researchers calculated that women who took hormonal therapy had a 7% lower risk of developing dementia than women who didn’t take hormonal therapy. The reduction in dementia risk was greatest for Black women ages 65 to 69.

The type of hormonal therapy the women took made a slight difference in reducing dementia risk. Women who took tamoxifen had an 11% lower risk while women who took an aromatase inhibitor had a 7% lower risk.

Because all the women in the study were age 65 or older, the results don’t apply to younger women. The researchers also can’t be sure whether any of the women in the study had a higher-than-average risk of dementia before they started taking hormonal therapy, since they did not collect information that would help them assess this risk.

Cai C, et al. Alzheimer Disease and Related Dementia Following Hormone-Modulating Therapy in Patients With Breast Cancer. JAMA Netw Open. 2024;7(7):e2422493.