Women outnumber men in heart failure with preserved ejection fraction, and the way body fat relates to the disease is not the same in both. A prespecified analysis of the SUMMIT trial asked whether tirzepatide works differently in each [1]. The trial's main result is covered in the heart failure composite.
The starting points really were different. Women had greater BMI, a higher waist-to-height ratio, worse symptoms on the Kansas City questionnaire, more severe functional class and shorter six-minute walk distances. Men had more left ventricular remodeling and more fat deposited around the heart. Higher waist-to-height ratio was associated with poorer kidney function in women only (interaction P = 0.043).
Despite all that, the drug behaved identically. Cardiovascular death or worsening heart failure gave hazard ratios of 0.66 in women and 0.61 in men with an interaction P of 0.81. Symptom scores improved by 8.1 and 5.5 placebo-corrected points (interaction P = 0.43), and walking distance by 18 and 15 meters (interaction P = 0.76). Because sex was a planned analysis rather than one dredged up afterwards, those nulls carry real weight.
If that holds up it has a practical edge. In a man with this condition, a modest weight response would not necessarily predict a modest symptom response, so stopping early because the scale is disappointing could mean stopping something that was working. In a woman the scale tracks the symptoms more closely. That is a hypothesis from one trial and not a prescribing rule, and it is the kind of finding that needs replication before anyone acts on it — the same caution applied in the semaglutide and tirzepatide comparison and the frailty analysis, which similarly found no heterogeneity where people expected some.
The broader point is worth keeping. Subgroup analyses usually get attention when they find a difference, and this one is more useful for what it failed to find: a disease that looks different in women and men responded to the same drug in the same way, which is a reason to treat rather than to hesitate. The body composition differences underlying it connect to what these drugs do to muscle.