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Prevention—science vs. nonsense

There are many ways in which cult medicine believers try to insinuate themselves into the health care system.  As Dr. Gorski has pointed out, “prevention” is one of their metaphorical feet in the door.  The cult medicine literature often says things like, “mainstream medicine is fine for treating acute illness, but what we do is prevention.” What they often leave out is the question of what “prevention” means, what the data on prevention is, and how to properly approach prevention.  It’s likely that one of my co-editors will touch on this topic in a bit more detail, but let me give you an introduction to the topic of prevention.

Definitions

Prevention is usually divided into three types: primary, secondary, and tertiary.

Primary prevention  refers to the prevention of diseases and conditions before their biological onset.  Examples of our most successful primary prevention interventions are clean water/sewerage and, ironically, vaccination.  I say “ironically” of course because so many of the altmed folks who talk about prevention are anti-vaccine.

Secondary prevention refers to the search for diseases that have not yet progressed to the point of causing overt disease, and intervening to prevent overt disease.  This  includes things like Pap smears, which look for early cervical cancers (which could have been primarily prevented by vaccination), mammography, which looks for early breast tumors,  and colonoscopy, which looks for early colonic neoplasms.  Secondary prevention is sometimes used synonymously with “screening”.

Tertiary prevention refers to the prevention of progression of and complications from existing disease.  For example, retinal and foot exams in diabetics prevent blindness and amputation very effectively.

Science

We know quite a bit about prevention.  As I mentioned, vaccination is a very powerful tool of primary prevention.  Let’s take another example, coronary heart disease (CHD).  We know quite a bit about primary and secondary prevention of this disease, one of the top two killers of Americans.  For example, quitting smoking drastically reduces a person’s chances of developing CHD.  Controlling blood pressure and cholesterol also drastically reduces the risk of developing CHD.  Physical activity and a lower calorie and lower sodium diet lower the risk of developing CHD, although using it as a sole intervention is not always adequate.

Secondary prevention is another area where science has taught us a lot.  We have excellent data on the benefit of certain drugs and certain blood pressure and cholesterol parameters in preventing progression of CHD.  Statin drugs used to lower cholesterol have been shown consistently to significantly lower the risk of cardiovascular events. We are getting quite good at this type of secondary prevention.  So-called lifestyle changes also play a role, but the size of their effect is likely much less than that of medical intervention.  Still, the two used together can be very effective.   Much of the data on lifestyle modification alone are from very small studies, and the data are not nearly as strong as that for quitting smoking, controlling cholesterol, or controlling blood pressure.

Tertiary prevention has been very successful.  For example, diabetics have a very high rate of lower extremity amputations.  Simple foot care programs can prevent most of these.

Nonsense

The alternative medicine community gives a lot of lip service to “lifestyle changes” and prevention, but data from them is very hard to come by.  For example, the U.S. Preventative Services Task Force has dozens of evidence-based recommendations on prevention. The National Center for Preventative and Alternative Medicine (NCCAM) has a page on cancer prevention, but most of it is about studies that have not yet been done, or interventions that have been unsuccessful.

The study of prevention is a science—we can’t just make it up as we go along.  When we give people recommendations on preventing disease, we better know what we’re talking about.  For example, beta-carotenes where thought to have anti-oxidant–and therefore positive–health properties.  It turns out that beta-carotene supplementation may actually increase the risk of some cancers.

When someone talks about prevention, making pretty-sounding promises isn’t enough.  They better make sure they have the data to back it up, or they may end up killing people.

Posted in: Public Health, Science and Medicine

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