Main Menu              Health Library                

ASPIRIN and CARDIOVASCULAR DISEASE               

Abstract:  Research now shows beyond reasonable question that the taking of 75 mg 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.   Note that aspirin even in this small amount can cause occasional serious internal bleeding and ulcers.

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.

Results from use of aspirin have been quite 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. Study 7A of 2005 found only a 9% (-3%-20%) risk for all cardiovascular events and most of this was for the age 65+ group. Although the statistical significance of this study was far too low to endorse the highly publicized conclusion that "aspirin was of no value to younger women" this does suggest that that the very low dose used every other day was insufficient to generate  the usual aspirin benefit. And because coronary disease risk is very low for younger women, its side effect of possible internal bleeding could make its use during these years of lesser value. Note that the usual dose of 325 mg/day is most beneficial for reducing risk of cancer.  Life Ahead uses a risk factor on coronary heart disease of 0.7 for baby type aspirin taken 4 or more times per week, by 0.9 for 2 times/week, and 0.85 for 3 times per week.  This acknowledges the poor results for very low dose aspirin.

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 aspirin tablets are needed for Heart Disease- BUT:  See the article on Cancer. For best protection from both major diseases, one regular 325 mg tablet is best.  Aspirin benefits coronary disease by reducing the blood clotting action of blood.  This cause of the disease is a chemical factor 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.   Study 7A of 2005 claimed a 24%(range 1%-41%)  benefit for small dose aspirin on stroke, and with this a mean benefit of perhaps 10% from all studies could be  statistically consistent with a result from all studies to date

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 75 mg is taken 4 or more times per week, and 0.85 if taken 3 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 75 mg 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.

Most health-interested person should be taking at least 75 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. But if any sign of excess or internal bleeding is noted, aspirin should not be used. In extreme cases some persons taking aspirin have died of internal bleeding that was not recognized.  A doctor's advise should be sought.