Aspirin and Cardiovascular Disease
As a result of a number of requests from readers of the Herald Journal, this current article’s intent is to examine and address the data from a new scientific publication about aspirin (ASA) and cardiovascular disease (CVD).
In the past couple of weeks, a new clinical study concerning ASA and CVD was presented to a large cardiology conference and then published in the prestigious medical journal, The New England Journal of Medicine. The results from this research made headline news in the national lay press by creating doubt and uncertainty about established and enduring science that says daily, low-dose ASA, is very effective in reducing the risk of CVD, particularly heart attacks and strokes, in people over 50 years of age.
First of all, this new relatively small investigation of short duration must be viewed and interpreted in the context of many larger studies covering decades of investigations that together make a strong case for ASA’s protective effects from CVD.
ASA has two main pharmacologic effects: first, it “thins” the blood by inhibiting platelets (clotting cells) from sticking together and thus inhibits clot formation inside arteries reducing the risk of most kinds of strokes and heart attacks (ischemic CV events). However, this same effect also increases the risk of bleeding, most commonly in the gut; secondly, ASA lowers the level of systemic inflammation in the body. We know that the process of inflammation contributes to atherosclerosis (plaque in arteries), the formation of some cancer cells, and dementia.
Historically, in the early 1980’s, a clinical trial involving thousands of participants showed that ASA reduced the incidence of heart attack and stroke by an astounding 35-40%. This data, along with knowledge of the pharmacologic effects of ASA as mentioned above, led many physician experts to recommend routine daily doses of ASA for most people over 50 years of age (with the exclusion of people with bleeding tendencies, aspirin allergy, or asthma). Additionally, publicity about these benefits along with the perceived safety of ASA, inspired many people to begin to self-administer ASA absent the recommendation of a physician. Subsequently, hundreds of clinical investigations confirmed these benefits to varying degrees.
At that time, the use of prophylactic ASA for middle aged and older people was indiscriminately recommended and these recs were not based on risk stratification. That is, encouraging ASA use was not selective nor dependent on a person’s risk or chance of developing CVD as compared to any adverse effects from taking the drug. Modern science and current research distinguishes two categories of prevention: Primary Prevention and Secondary Prevention. When ASA is used prophylactically in healthy people with low risk for CVD and no history of CV events (such as heart attack), this treatment is called Primary Prevention. When used in high risk people with a history of a previous CV event, it is referred to Secondary Prevention.
Since trials have been segregated into these categories, results from secondary prevention studies have shown ASA unequivocally beneficial in preventing recurrent CV events. There has been benefit in primary prevention trials, but all results not as dramatic.
ASA has always been assumed to be safe, but most recent studies have traced the incidence of its most serious and common side effect-bleeding. Most of these results have shown that bleeding was much more common in ASA treated groups than the placebo groups. Reviewing the source of bleeding in most of the trials, the most common bleeding involves the GI tract and the great majority of these bleeds were not life-threatening nor disabling. Some of the summaries in the Primary Prevention Trials stated that this risk outweighed the benefits. However, consideration must be given to the fact that most of the side effects were not critical and not preventing a CV event certainly can be disabling with some fatal outcomes up to 50%.
The current study showed no benefit in preventing CV events in participants that used ASA. However, it must be noted that the participants in this trial were very low risk (no known significant atherosclerosis, no family history of CVD, no diabetes, no smokers) and a great majority of them were being treated with anti-hypertensives for elevated blood pressure, statins for cholesterol lowering and pursuing an ideal life style for preventing CVD (exercising and maintaining ideal body weight). The overall rate of CV events for the ASA and the placebo treated group was 50% less than expected from the general population. It is not surprising that ASA was not able to contribute CV protection in this group of participants.
The incidence of bleeding was higher in the ASA treated group, but once again, the overall rate of bleeding for all participants was very low. Most of the bleeds were relatively benign and the investigators included nose bleeds as “critical bleeds”.
This study does not lessen the potential benefit of using ASA for protection against CVD. However, before continuing or beginning daily ASA for CV protection it is wise to consult with your personal physician.
Dr. Tippett is founder of Comprehensive Quality Healthcare Providers, a concierge internal medicine practice, located at 1210 Commerce Dr. Suite 106 Greensboro, Ga. 30642. He can be reached at 706-510-3659. Visit his website at www.drtippett.com