The One Place People Felt Better

Across 43 trials and 45,663 participants, no obesity drug improved quality of life enough for patients to notice. In two trials of heart failure with preserved ejection fraction, both drugs produced large improvements on a symptom score.^[1][2] Those findings look contradictory and are not, and the reason is worth understanding — it is about which question the questionnaire asks.

What these trials measured

Heart failure with preserved ejection fraction is a condition where the heart pumps normally but cannot fill properly, and in its obesity-related form it produces breathlessness, exhaustion and a shrinking radius of what someone can do. Until recently nothing was approved to treat it.

Both trials used the Kansas City Cardiomyopathy Questionnaire as a primary endpoint — a score from 0 to 100 built specifically from the symptoms and physical limitations of heart failure. Higher is better, and a difference of roughly five points is generally treated as the smallest a patient would notice.

Both symptom differences clear the threshold for a change patients notice, and both were highly significant. In STEP-HFpEF the row that stands out is the last one for that column: serious adverse events occurred half as often on the drug — 13.3% against 26.7% — which in this population largely means heart failure events.

Why this is not a contradiction

Elsewhere we have reported, twice, that these drugs do not improve quality of life — across 262 trials, no agent cleared the threshold, and in the head-to-head trial the mental component did not move in either arm.

That resolves the apparent conflict and narrows the claim in a useful way. There is no good evidence that these drugs make people feel better in general. There is good evidence that in obesity-related heart failure they relieve the symptoms of that condition — which is a smaller, more specific, and better-supported statement.

Feeling better in general and feeling less breathless are different questions, and only one of them has been answered yes.

Decompose the composite

SUMMIT’s headline outcome was a composite — cardiovascular death or a worsening heart failure event — and it came in at a hazard ratio of 0.62. Composites should always be taken apart, and this one comes apart in an instructive way.

The benefit is carried entirely by worsening heart failure events. The mortality component points the other way — more cardiovascular deaths on the drug than on placebo.

Adverse events led 6.3% of the tirzepatide group to stop, against 1.4% on placebo — mainly gastrointestinal, as everywhere in this class.

What these two trials do not do

• They do not compare the drugs. Two separate trials, different populations, different placebo arms. A comparison exists and is observational — and found no meaningful difference between them.
• They enrolled people with obesity — a BMI of 30 or more — so they speak to obesity-related heart failure specifically.
• STEP-HFpEF ran 52 weeks; SUMMIT followed people a median of 104. Neither is long for a chronic condition.
• Each was funded by the maker of its drug, Novo Nordisk and Eli Lilly respectively.