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ASPIRIN and CARDIOVASCULAR DISEASE               

Abstract:  Research now shows beyond reasonable question that the taking of one 75 or 81 mg pill of Aspirin (the usual Aspirin pill is 325 mg) 4 or more times per week will reduce the risk of coronary heart disease by about 30%.  Aspirin benefits mostly by reducing the blood clotting action of the blood.  Aspirin benefits individuals free of coronary disease as well as those who have survived coronary disease attacks. But Aspirin does not reduce risk of stroke significantly.  A review of major research and of some meta or summary analyses of Aspirin research follows. See accompanying discussion showing that Aspirin probably in somewhat larger amounts also can reduce risk of cancer.   But Aspirin even in this small amount can cause internal bleeding and ulcers in some people.

Aspirin as a means to reduce risk of cardiovascular diseases has been studied extensively now for more than 3 decades.  More than 31,000 studies involving aspirin now are listed in the Medline references, and results of at least 150 randomized clinical trials plus some important prospective studies research have been published.  Aspirin also appears to reduce risk of some cancer.  See the separate health library discussion of Aspirin and Cancer.

Research results on use of aspirin have been remarkably consistent.  In nearly every study of substantial size the regular daily use of aspirin reduces risk of coronary heart disease by close to 30% for a risk factor of 0.70.  Table A following provides a review of some principal studies and summary analyses of results for use of aspirin.  Studies #1 through 7 include an average result of 25 trials, results of several Meta analyses of groups of randomized clinical studies, and results of two important prospective studies.  Results of each listed review or study are in near close accord.  And results on coronary disease patients as studies #15 and 16 show a similar benefit.  Benefits appear to be near similar for men and women and for those younger and older.

Stroke Benefits Little from Aspirin:  Most research shows that aspirin benefits ischemic or ‘artery clogging’ related stroke but increases the risk of hemorrhagic stroke.  Overall, use of aspirin appears to have little if any overall benefit in reducing risk of stroke.  An overall risk ratio of either 0.90 or 1.00 would be near statistically consistent with the results shown for studies #9 through #14 on stroke. 

Only 1/4^th size usual (often 75 mg in Europe and 81 mg in the US) aspirin tablets are needed for Heart Disease- but a regular pill may be best to reduce risk of cancer.   Aspirin benefits coronary disease by reducing the blood clotting action of blood.  This effect on risk of the disease appears to be due to a direct biochemical process that can provide benefit promptly.  Thus useful results on aspirin are far easier to obtain that are results on antioxidant vitamins that reduce atherosclerosis and require 7-10 years of use before a substantial benefit can develop. Benefits from aspirin appear even in a 1 year trial, a time of use that will produce no measurable benefit for an antioxidant.  Because of this - and unlike those for antioxidants - results for aspirin from shorter term clinical trials are similar to those obtained in longer term observation studies.

Of particular interest is the fact that aspirin can provide benefits to survivors of coronary disease, and that these benefits are supplementary to those from the potent anti-clotting drug warfarin. Study #15 done in the UK showed that either aspirin or warfarin taken individually reduced risk of recurrent disease and death by 20%, or a risk factor of 0.79-0.80.  Taken together, risk was reduced 34%.  Aspirin and warfarin must reduce clotting via differing mechanisms.

C-reactive Protein Appears Involved:  A most interesting recent finding about aspirin is that its benefit may depend substantially or even entirely on the level of artery inflammation as indicated by the marker C-reactive protein (CRP).  Ridker’s study #8 in Table A following showed that aspirin had no benefit at very low CRP values but produced increasing benefit as CRP level was increased.  For reference, an average population CRP may be about 1.2 mg/l and at this level study #8 results shows a risk ratio of about 0.60, well within statistical range of the average population risk of 0.70 for aspirin.  It is well recognized now that plaques that develop in arteries tend to develop at regions of artery disturbance, and that blood clots form at such sites that can break off and stop blood flow.

At least one recent study found that use of ibuprofen in combination with aspirin may have cancelled aspirin’s benefit via anti-clotting. This suggests that if both these agents are taken, they should be taken at differing times of a day.  This may or may not reduce the interaction, and more research on this is needed.

Life Ahead now credits coronary heart disease with a risk factor of 0.70 if aspirin if a 75 mg or 81 mg or larger dose is taken 4 or more times per week.  No credit or debit is given to stroke. As before, see the separate discussion on Aspirin and Cancer.  Aspirin does have side effects in promoting ulcers, gastritis and bleeding.  Some can experience this even at the low daily dose and more experience the problem with the 325 mg daily dose.   Thus individuals must consult their doctors in event of any such problem as to desirability of considering aspirin use or moving to some alternate.

Any health interested person should be taking at least 75-81 mg and preferably a usual 325 mg tablet of aspirin each day for health protection unless this creates unacceptable other problems, or is advised otherwise medically.