Long-term, daily use of aspirin to prevent blood clots in very elderly patients leads to an increased risk of serious or fatal internal bleeding, say researchers.

Heartburn medication allows people 75 years and older to keep the preventative benefits of aspirin while avoiding its dangerous side-effects, says the report in the medical journal The Lancet.

Even among people with no history of heart problems or stroke, the risk of gastrointestinal bleeding goes up with age for aspirin users, other research has shown. Roughly half of all adults 75 (and over) in the US and Europe take small daily doses of aspirin – ranging from 75 to 150 milligrams – or other clot-inhibiting drugs. A normal dose for a headache is 325 to 600mg.