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Sunday, January 15, 2012

Some interesting new studies: Should you take aspirin to prevent heart attacks? Do statin medications cause diabetes? Does marijuana smoking cause lung disease?

This week has been really interesting in the medical journals. Although I often question the relevance of population based medical research to guide treatment of individuals, large trials are excellent for helping us question widely held beliefs. Since doctors are often unreasonably convinced that they are right, studies that make us question ourselves are valuable.

Last year when reviewing recommendations of the US Preventive Services Task Force and looking at the studies on which these recommendations were based, I began to recommend regular use of aspirin for men over the age of 45 and women over the age of 55 to prevent heart attacks. This month an article came out in the Archives of Internal Medicine that showed that for patients without heart disease, there was no decrease in  mortality with regular aspirin use and that the reduction in risk of heart attack and stroke is really quite small. Risk of bleeding related to taking even a baby aspirin is significant. This only leads me back to my previous position on the subject, which was that each individual should look at his or her risk for heart attack and stroke and weigh their risk associated with aspirin use and then decide if using it will make sense. The USPSTF had labeled aspirin use as a level A recommendations, suggesting that there was good medical evidence that it helped. They will probably change that, but usually those changes take awhile.

Use of statins for primary prevention of heart disease (that is prevention of heart attack or angina in patients who are not already known to have coronary artery disease) has been something I have hesitated to recommend. Statins, such as lipitor, have such powerful effects on so many systems that using them in patients who are otherwise healthy worries me. Cardiologist seem to be positively enamored of statins, and it seems that very little time passes between studies that show yet another benefit of statin therapy. As a primary care physician I saw many patients with side effects of statins, including muscle pains and stomach problems, many of which were not recognized as side effects until the medication was stopped. It just can't be good to take something that makes you feel miserable, even if that something doesn't kill you or cause organ failure. Many of my patients voted with their feet on the statin issue and just quit taking the medicine even after I had prescribed it and made a good case for using it. Statin safety was addressed in an article, again in the Archives of Internal Medicine this month that showed that in the Womens' Health Initiative patients on statins had about a 1.5 times average risk of developing diabetes. This was corrected for such issues as weight and other known risk factors. I can imagine that such a finding might still be just an association, since doctors might have put patients on statins due to perception of their risk for diabetes since diabetes often goes hand in had with elevated cholesterol levels. Still, I harbor ongoing suspicion of statin drugs since their manufacturers have made such an obscene amount of money on them which in turn fuels more advertising and feeds back to influence both clinicians and researchers. It will be interesting to see how this piece of data pans out since diabetes is hardly an acceptable medication side effect.

Finally, in the Journal of the AMA (JAMA) an article addressed the lung risks of long term marijuana smoking. An Article in the Archives of Internal Medicine in 2007 reported that marijuana dilated the small airways, which would tend to be a good thing, but was only able to say that long term smokers of marijuana often had a productive cough. In this article, pulmonary function testing was done regularly in a group of over 5000 patients who were being followed to look at risk of heart disease. These patients had periodic testing of lung function and, on average, low frequency but long term use of marijuana was not associated with lung disease and even frequent marijuana use was not clearly bad for the lungs. Marijuana smokers did have an increase in lung capacity that was theorized to be due to the fact that they learned how to take deeper breaths. I have certainly seen patients who have lung disease that looks much like that of my tobacco smokers even though they only use marijuana, and studies like this do not prove that marijuana is safe for everyone's lungs. Still, marijuana use is by no means equivalent to cigarette use in terms of respiratory complications. I suspect we will never see a study that looks at effects of smoking the amount of marijuana equivalent to a pack of cigarettes a day. Other complications of that level of use would probably eclipse breathing issues.

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