Should people with diabetes and heart disease be on tirzepatide?
Yes, based on this study. Over one year, 2.9 percent of people taking tirzepatide had a major heart event, compared with 4.4 percent of people taking a drug with no heart effect. That is 1.4 fewer events for every 100 people treated, or about 14 fewer per 1,000.
Tirzepatide is the drug sold as Mounjaro and Zepbound. It is used for type 2 diabetes and for weight loss. Doctors have known it lowers blood sugar and body weight. What we have not known is whether it actually prevents heart attacks and deaths in people who already have heart disease. This study set out to answer that question using real patient records.
The researchers put the number in a form you can use. To prevent one major heart event, about 70 people would need to take tirzepatide for a year. That figure is called the number needed to treat. A smaller number means the drug helps more people.
What the Data Show
The overall drop in major heart events worked out to about 32 percent lower risk (hazard ratio 0.68). The range around that estimate makes it very likely the true benefit is somewhere between 20 percent and 42 percent lower (95% CI 0.58 to 0.80). A “major heart event” here meant a heart attack, a stroke, or death from any cause.
Breaking that apart tells you where the benefit came from. Heart attacks fell by about 33 percent (hazard ratio 0.67, 0.52 to 0.87), which works out to about 130 people treated for a year to prevent one. Death from any cause fell by about 45 percent (hazard ratio 0.55, 0.42 to 0.72), with about 122 people treated to prevent one death. Ischaemic stroke, the kind caused by a blocked vessel, showed no meaningful difference (hazard ratio 0.91, 0.64 to 1.28).
Then came the surprise. Infections serious enough to land someone in the hospital were about 36 percent lower with tirzepatide (hazard ratio 0.64, 0.55 to 0.75), and about 48 people would need to be treated for a year to prevent one. Death related to infection was about 60 percent lower (hazard ratio 0.40, 0.26 to 0.61). Nobody expected that from a diabetes drug.
Dr. Kumar’s Take
I find the size of the death benefit hard to ignore. A 45 percent drop in all cause mortality over a single year is a big claim for any drug, and I hold big claims to a higher bar. What makes me take this one seriously is the design. The researchers compared tirzepatide against sitagliptin, a diabetes drug already shown to have no effect on the heart either way. That gives you something close to a placebo comparison inside real medical records.
The infection finding is the part I keep coming back to. If tirzepatide really does cut serious infections and deaths from infection, then the heart benefit may not be entirely about arteries. Something broader may be going on. That is a hypothesis, not a conclusion, and I want to see it repeated before I build anything on it.
Study Snapshot
The team followed 52,971 US adults aged 40 and older who had type 2 diabetes and established atherosclerotic cardiovascular disease, meaning plaque buildup in the arteries that had already caused a problem. Of those, 35,353 started tirzepatide and 17,618 started sitagliptin. The data came from two national US insurance claims databases, covering May 2022 through May 2025.
The two groups were matched so that the people in them looked alike at the start on measured characteristics. Follow-up ran until an event happened, until someone left their health plan, until they stopped or switched drugs, or until one year passed, whichever came first.
How strong is the evidence?
This is not a randomized trial. People were not assigned to a drug by chance, so hidden differences between the groups can always tilt the result. The researchers tried to catch that using what are called negative control outcomes, conditions the drug should have no effect on at all. They tested lumbar radiculopathy, a pinched nerve in the lower back, and abdominal hernia. Neither showed any association with tirzepatide, which is what you want to see. If those had shifted too, it would suggest the groups differed in ways nobody measured.
Follow-up also stopped at one year, and it stopped when people quit or switched drugs. So this tells you about the first year of treatment in people who stayed on it. It does not tell you what happens over five or ten years.
Practical Takeaways
- If you have type 2 diabetes and known heart disease, ask your doctor whether tirzepatide fits your treatment plan, since this study looked specifically at that group and not at healthy adults.
- Understand that the benefit here is real but modest in absolute terms, with about 70 people needing treatment for a year to prevent one major heart event.
- Do not stop a statin, blood pressure medication, or any other heart drug because of this study, since tirzepatide was added on top of standard care, not used in place of it.
- Keep your vaccinations current and take infections seriously regardless of what you take, because the infection finding here is new and has not been confirmed elsewhere.
Related Studies and Research
- A plant-based diet lowered heart disease risk over 20 years
- Treating gout properly may cut heart attack and stroke risk by up to 23%
- Eating eggs regularly linked to lower Alzheimer’s risk in older adults
- Ultra-processed foods linked to 47% higher heart disease risk
FAQs
Does tirzepatide prevent strokes?
Not in this study. Ischaemic stroke showed no meaningful difference between the two groups, with a hazard ratio of 0.91 and a range wide enough to include both a benefit and a small harm (0.64 to 1.28). That does not prove tirzepatide has no effect on stroke. Strokes were less common than the other outcomes over a single year, and when events are rare, it takes more people and more time to detect a real difference. The heart attack and mortality signals were clear here; the stroke signal was not.
Why did the researchers compare tirzepatide to sitagliptin instead of nothing?
You cannot ethically leave people with diabetes and heart disease untreated just to create a comparison group. Sitagliptin solves that problem. It is an approved diabetes drug that has already been tested in trials and shown to have a neutral effect on cardiovascular outcomes, meaning it neither helps nor hurts the heart. That makes it what researchers call a placebo proxy. Comparing against it lets you estimate the added heart benefit of tirzepatide on top of ordinary care.
Is a 32 percent risk reduction as impressive as it sounds?
It depends on your starting risk, which is exactly why the absolute numbers matter more. In this group the yearly risk of a major heart event dropped from 4.4 percent to 2.9 percent. That is meaningful for people who already have heart disease, because their baseline risk is high. Someone with a much lower starting risk would see a much smaller absolute gain from the same relative reduction. Always ask for the absolute numbers when a drug is described in percentages.
Bottom Line
In 52,971 US adults with type 2 diabetes and established heart disease, starting tirzepatide cut the one year risk of a major heart event from 4.4 percent to 2.9 percent, driven by fewer heart attacks and fewer deaths. About 70 people would need to take it for a year to prevent one event. The drop in serious infections and infection related deaths was not expected and points toward mechanisms beyond the arteries. This was an observational study rather than a randomized trial, so it estimates what the benefit is likely to be rather than proving it outright.
