“The Physicians' Health Study is a double-blind, placebo-controlled, randomized trial designed to test two primary-prevention
hypotheses in a population of healthy male physicians: whether aspirin in low doses (Bufferin, Bristol-Myers Products, 325
mg every other day) reduces mortality from cardiovascular disease, and whether beta carotene (Lurotin, BASF, 50 mg on alternate
days) decreases the incidence of cancer. Every six months for the first year and annually thereafter, the participants were
sent a supply of monthly calendar packs (provided by Bristol-Myers Products) containing white tablets (aspirin or placebo)
for odd-numbered days and red capsules (beta carotene or placebo) for even-numbered days. They were also sent brief questionnaires
asking about their compliance with the treatment regimen and the occurrence of any relevant events. By January 25, 1988, the
participants had been followed for an average of 60.2 months (range, 45.8 to 77.0); 99.7 percent were still providing information
on morbidity, and the vital status of all 22,071 doctors was known. The reported consumption of aspirin or other platelet-active
drugs was 85.71 percent in the aspirin group and 14.23 percent in the placebo group. A total of 1269 physicians (624 taking
aspirin and 645 taking aspirin placebo) requested an enteric-coated preparation (supplied by Bristol-Myers Products), and
an additional 29 (16 assigned to aspirin and 13 assigned to placebo) specifically requested Ecotrin or its placebo (supplied
by Smith-Kline Beckman). Although the beta carotene component of the trial is continuing at least through 1990, the Data Monitoring
Board recommended the early termination of the blinded aspirin component of the trial on December 18, 1987. This decision
was based on all available evidence, including three major considerations: the presence of a significant (P<0.00001) reduction
in the risk of total myocardial infarction among those in the aspirin group;… There were 139 myocardial infarctions
among those assigned to aspirin and 239 among those assigned to aspirin placebo (relative risk, 0.56; 95 percent confidence
interval, 0.45 to 0.70; P<0.00001) (Table 1). This represents a 44 percent reduction in risk, and the benefits of aspirin
were significant for both fatal and nonfatal myocardial infarction. In terms of absolute rates of events, the figures can
be extrapolated to 254.8 per 100,000 per year in the aspirin group and 439.7 per 100,000 per year in the placebo group….
Altogether, 11,037 physicians were assigned at random to receive aspirin and 11,034 to receive aspirin placebo….
Further analyses showed that the reduction in the risk of myocardial infarction was apparent only among those who were 50
years of age and older. The benefit was present at all levels of cholesterol, but appeared greatest at low levels. The relative
risk of ulcer in the aspirin group was 1.22 (169 in the aspirin group as compared with 138 in the placebo group…
For cholesterol, the beneficial effects of aspirin were apparent at all levels. The observation that the benefits of aspirin
for myocardial infarction were greatest at low levels of cholesterol was unexpected….. Most recently, the Second
International Study of Infarct Survival17 evaluated the role of aspirin in evolving myocardial infarction in a randomized
trial with 17,187 participants and demonstrated a 49 percent reduction in nonfatal myocardial infarction, a 46 percent decrease
in nonfatal stroke, and a 23 percent reduction in cardiovascular death after five weeks. All these reductions were statistically
significant… cardiovascular mortality rate among the physicians in this trial was only 15 percent of that expected
for a general population of white men with the same age distribution over a similar period…[From table 1.. Total
heart attacks aspirin cohort 139, placebo 238, or 1/3rd of heart attacks in the aspirin group, and 2/3rd placebo groups.]
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