If you are female, you might check out the recent study that indicated low dose aspirin had mixed effects on women's risk of stroke, cardiovascular disease and death.
You can read about the results from the Brighamandwomens.org website.
A quote from the above article:
"In March 2005, long-awaited WHS results demonstrated regular low-dose aspirin therapy reduced the risk of stroke by 17 percent, but did not decrease heart attacks or cardiovascular deaths among all women. However, in the subgroup of women 65 years and older, aspirin reduced the risks of developing overall cardiovascular disease, ischemic stroke and heart attack."
One more thing he said was that there is no additional benefit of taking more than 75 mg per day for heart attack/stroke prevention. That is why the limit of 81 mg (baby aspirin) per day. Higher doses such as 325 mg daily over long periods of time can cause damage to the kidneys. Hence no more than 81 mg per day and the advice to drink lots ( 8 glasses or more) of water per day to keep kidneys safe. My $0.02 based on my understanding of what my doc said.
They did a study in France, giving 98 patients 160 mg. aspirin/day and evaluating the platelet response (did they get less sticky.) TWENTY-NINE showed no response to this dosage...they were resistant to aspirin therapy.
These 29 were then put on 300 mg. aspirin and all but 11 of them showed the desired platelet reponse.
Thus, to extrapolate this study, there are approximately 18% of the population that needs at least 300 mg. to achieve platelet control sufficient to lower heart attack risk...and probably some portion of the resistant 11% that needs even MORE, but that's conjecture....they didn't test the final 11.
I maintain that this is GOOD evidence, unless there is a good reason to the contrary, that taking a 325 mg. pill is a wise way to go...I take 650 mg.
Perhaps if one notices an increased tendency to bleeding from 85 mg. then such a person has proven the low dose is working for him.