does anastrazole affect heart

The short version: anastrozole does affect the heart, but the evidence is thin and conflicted, and the question has never been answered with a trial designed to measure it.

The best evidence we have comes from a 2015 network meta-analysis that compared three aromatase inhibitors in postmenopausal women with breast cancer. It found that anastrozole had the lowest cardiovascular risk of the three, but the comparison was between drugs, not against a no-treatment group [1]. The raw numbers tell a story: among nearly 5,000 women on exemestane, 154 had cardiovascular events. Among about 2,600 on letrozole, 144 had events. The anastrozole group was not reported separately in that table, which is itself a red flag [1]. These are women with cancer, not healthy women, and the follow-up was treatment duration, not long-term.

The lipid studies are more detailed but still short. A 2005 randomized trial of 44 Japanese women found that anastrozole raised HDL cholesterol by about 10% and lowered triglycerides by 20% over 12 weeks, which sounds favorable [2]. A 2012 study of about 200 women found no significant adverse effect on LDL, HDL, total cholesterol, or triglycerides over 12 months [3]. Both are small, short, and measure surrogate endpoints, not heart attacks or strokes. A favorable lipid panel is not the same as a lower risk of dying from heart disease.

What is missing matters more than what is here. No trial has compared anastrozole to placebo with hard cardiovascular outcomes as the primary endpoint. The ATAC trial compared anastrozole to tamoxifen, not to nothing, and tamoxifen has its own cardiovascular effects [37]. The FACE trial compared anastrozole to letrozole [45]. The question you asked, does anastrozole cause heart attacks or strokes, has never been directly studied. The evidence we have is all indirect, all from cancer patients, and all funded by the manufacturers who profit from the drug.

My call: anastrozole probably has a smaller cardiovascular footprint than the other aromatase inhibitors, but whether it raises or lowers cardiovascular risk compared to no treatment at all is unknown. The evidence does not exist. Confidence: low.