Most people know that aspirin can reduce blood clots and thus the risk heart attack, as shown famously in the 1989 “Physicians’ Health Study” where 22,000 male physicians were randomly assigned to either a regular aspirin (325 mg) every other day or an identical looking placebo. The results are shown in the table below, where “Myocardial Infarction” or “MI” is doctor-speak for heart attack.

Treatment	Myocardial Infarctions	No Infarction	Total	fraction with MI
Aspirin	139	10,898	11,037	139/11,037 = 0.0126
Placebo	239	10,795	11,034	239/11,034 = 0.0217

Over the 5 years of the study, the physicians had 378 MI events, but mostly in the group that didn’t take aspirin: 1.28% of the doctors who took aspirin had a heart attack as opposed to 2.17% for those with the placebo. The ratio 1.28/2.17 = 0.58 is called the risk ratio. Apparently, aspirin in this dose reduces your MI risk to 58% of what it was otherwise — at least in white males of a certain age.

Further study showed aspirin benefits with women and other ethnicities, and benefits beyond hear attack, in any disease that induces disseminated intravascular coagulopathy. That’s doctor speak for excessive blood clots. Aspirin produced a reduction in stroke and in some cancers (Leukemia among them) and now it now seems likely that aspirin reduces the deadliness of COVID-19. Data from Wuhan showed that excessive blood clots were present in 71% of deaths vs. 0.4% of survivors. In the US, some 30% of those with serious COVID symptoms and death show excessive blood clots, particularly in the lungs. Aspirin and Vitamin D seem to help.

.The down-side of aspirin use is a reduction in wound healing and some intestinal bleeding. The intestinal bleeding is known as aspirin burn. Because of these side-effects it is common to give a lower dose today, just one baby aspirin per day, 81 mg. While this does does some good, It is not clear that it is ideal for all people. This recent study in the Lanset (2018) shows a strong relationship between body weight and aspirin response. Based on 117,279 patients, male and female, the Lanset study found that the low dose, baby aspirin provides MI benefits only in thin people, those who weigh less than about 60 kg (130 lb). If you weigh more than that, you need a higher dose, perhaps two baby aspirin per day, or a single adult aspirin every other day, the dose of the original doctors study.

In this study of COVID patients, published in July, those who had been taking aspirin fared far better than those who did not A followup study will examine the benefits of one baby aspirin (81 mg) with and without Vitamin D, read about it here. I should note that other pain medications do not have this blood-thinning effect, and would not be expected to have the same benefit.

While it seems likely that 2 baby aspirins might be better in fat people, or one full aspirin every other day, taking a lot more than this is deadly. During the Spanish flu some patients were given as much as 80 adult aspirins per day. It likely killed them. As Paracelsus noted, the difference between a cure and a poison is the dose.

Robert Buxbaum, November 27, 2020.