risk of dementia among postmenopausal breast cancer survivors treated with aromatase inhibitors versus tamoxifen: a cohort study using primary care data from the uk

Among a cohort of postmenopausal breast cancer survivors, we aimed to compare the risk of dementia associated with aromatase inhibitor (ai) therapy versus tamoxifen. using uk primary care electronic health records, we identified 14,214 postmenopausal breast cancer survivors (aged ≥ 54 years) with a first ai or tamoxifen prescription between 2002 and 2015 and no previous dementia diagnosis. women were followed-up to identify incident cases of dementia. cox regression was used to calculate hazard ratios (hrs) with 95% confidence intervals (cis) to quantify the association between ai exposure (vs. tamoxifen) and dementia, adjusted for confounders. a total of 368 incident dementia cases was identified over 57,102 person-years of follow-up. the crude incidence rate of dementia was 7.46 per 1000 person-years (95% ci 6.43–8.65) among women starting endocrine treatment on an ai, and 6.32 per 1000 person-years (95% ci 5.34–7.47) among women starting on tamoxifen. after accounting for age differences and assessing other potential confounders, there was no evidence of a difference in dementia risk between exposure groups (hr for ai vs tamoxifen 1.04, 95% ci 0.83–1.03). there was no evidence of effect modification by age. there was no evidence for a difference in dementia risk between ai and tamoxifen users among postmenopausal breast cancer survivors. our findings suggest that there is no reason for concern about a difference in dementia risk with ai vs. tamoxifen, which is relevant to postmenopausal breast cancer patients recommended these treatments.