An aspirin tablet is like a key that doesn't fit every lock. For a long time, scientists couldn't work out why aspirin helps some older people live longer without disability while leaving others no better off. It turns out the shape of the lock is what matters: in people with diabetes, excess weight, and high blood pressure, that is, those at high risk of heart and metabolic disease, the key turns.
The study included 1270 older Black and Latino adults in the United States. The researchers built a model that predicted who exactly would benefit from aspirin. The model sorted people into three groups. In the group that stood to gain the most, aspirin cut the risk of losing a healthy life by 11.1 percentage points over five years. In the second group the effect was weaker, and in the third there was no benefit at all, with some people even trending toward harm.
Previously it was unclear why aspirin showed no benefit on average. Now it makes sense: the benefit is confined to people at high cardiometabolic risk. For now, this knowledge can't be used in the clinic: it needs to be tested against other data. But if that test holds up, a doctor could tell in advance whether the key fits a particular patient's lock.
In the group with the highest predicted benefit from aspirin, participants were more likely to live alone but had stronger grip strength. Grip strength is considered a marker of overall health and survival in older adults.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.