Charles Hennekens of Harvard Medical School led one of the studies. In nineteen eighty-three, he began to study more than twenty-two thousand healthy male doctors over forty years of age. Half took an aspirin every other day. The others took what they thought was aspirin. But it was only a placebo, a harmless substance.
Five years later, Doctor Hennekens reported that people who took aspirin reduced their risk of a heart attack. But they had a higher risk of bleeding in the brain than the other doctors.