Major risks of bleeding in people who consume aspirin on a daily basis overwhelm its benefits.
According to principal investigator of the study, John McNeil, who is head of Monash University's Department of Epidemiology and Preventive Medicine, the results of the trial will result in a rethinking of global guidelines relating to the use of aspirin to prevent common conditions associated with ageing. Instead, it actually increased participants' risk of "significant bleeding in the digestive tract, brain, or other sites that required transfusions or admission to the hospital", the Times reported.
The researchers studied over 19,000 people over the age group of 65 and 70 who were asked to take aspirin or placebo over a period of four and half years.
But it had been unclear whether healthy people older than 70 would derive the same benefit. The new study was created to find out whether low-dose aspirin could prolong healthy, independent living in seniors who had not shown signs of heart disease.
While evidence remains strong that baby aspirin therapy aids in preventing a second heart attack or stroke, the study explored whether a first heart attack can be prevented by the small amount of blood thinners in aspirin.
The participants were then followed for an average of 4.7 years.
One surprise for the researchers was that the group that took aspirin died at a slightly higher rate from all causes than the group that did not take it. Rates of people who suffered from disability and dementia were almost the same. The rates of coronary heart disease, heart attacks and strokes were also similar.
There was little difference in these measures between the 9589 patients in the placebo group and the 9525 in the aspirin group.
Half of them were asked to take 100mg of aspirin a day, while the other half took a placebo.
While there were 21.5 cases of death, dementia or disability per 1,000 patients each year in the aspirin group, the rate was 21.2 with placebo. This finding was surprising because nearly half of those extra deaths were due to cancer, including colorectal and other gastrointestinal cancers. "It is possible pre-existing cancers may have interacted with the aspirin".
Over the next four years, almost 20,000 people mostly over the age of 70 in both Australia and the United States were recruited for the trial. However, more research was needed to investigate its use more thoroughly.
Cardiologist Dr. Erin Michos called the results, "alarming", saying that aspirin should be prescribed only selectively. Patients now get statins to lower cholesterol and anti-hypertensive medications to lower blood pressure.
The clinical trial did not include people who take aspirin for medical reasons as advised by their doctor, including those who have already suffered a heart attack or stroke.
Consultant cardiologist Dr Aseem Malhotra said: "For the treatment of heart disease, or for those who have suffered heart attacks, aspirin has been a "wonder drug".
"Some of them will say, 'if it ain't broke don't fix it, '" predicted Huffman, an associate professor of preventive medicine in the division of cardiology at Northwestern University's Feinberg School of Medicine and a cardiologist at Northwestern Medicine.