Sunday, April 25, 2010

When is a Low Salt Diet Beneficial (if ever)

I was upset, both from a medical and a mathematical point of view, after I read the paper published in "Annals of Internal Medicine" by Crystal Smith-Spangler and others: "Population Strategies to Decrease Sodium Intake",Ann.Int.Med. 2010;152:481-487, the lead article in the Annals volume published on April 20 of this year. I have been a reviewer for Annals for over 10 years. I can assure you that I would have rejected this article immediately. I never had an article I rejected overridden by the editor-in-chief, but sometimes the article in question would be published in a journal with less strict criteria.

I object to this paper on epidemiological grounds, on mathematical grounds, and on moral grounds as well.I think we all agree that blood pressure is a monotonically increasing function of the amount of daily NaCl consumption. We also note that increased blood pressure puts one at risk for strokes (CVA's) as well as heart attacks (MI's). The question of course is twofold: does lowering blood pressure reduce the risk or rate of CVA's and MI's? And furthermore, by how much can we reduce blood pressure "the silent killer, by decreasing the salt in the diet.

I will pass over the fact that some heart failure patients on NY Class III or IV worsen their faliure when their salt intake is lessened. I will also ignore the fact that there is no city-wide Institutional Review Board to evaluate the safety of this intervention in various groups of patients, and, of course, the "patients" in an entire city or country are not all consulting adults. So we are treating/testing a group of involuntary "volunteers".

Since correlation is NOT causation, we first have to see if lowering dietary salt lowers cardiovascular events (presumably by lowering blood pressure). Giving a patient a diuretic makes his kidneys excrete extra salt, so a daily water pill mimics a low salt diet somewhat. The result of diuretic treatment to lower blood pressure was that the incidence of CVA's was reduced. but not that of MI's.

To add further spice to the stories, the authors claimed that a 9.7% reduction in salt intake, as achieved by the British Government, would attain a 1.25mm (i.e. 1%) reduction in systolic blood pressure, and this would prevent 513,885 strokes and 480,358 heart attacks.

This not only looks too good to be true, it is too good to be true. The intra-observer error/statistical deviation in measuring blood pressure is+/- 2 mm.The interobserver error is worse, and is +/- 3 to 4 mm. Hg. (Not unlike the radiologist ' mammogram report that says they miss 10% of cancers). This would be similar to my claiming that since the measured speed of light is 186,272 miles/second, and I measured it to be 186,273 +/- 2 miles/sec., it is time to change the accepted value of the speed of light.

This is also like the situation where the government, seeing that pumping auto brakes helps to reduce the skidding of a car insisted on installing an automatic pumping system on the brakes, the ABS. You got a car insurance reduction for doing this,but it did not decrease the number of accidents after a skid, and now it is no longer mandatory. I also am skipping over the fact that the NTSB knew that if they required air bags to explode/expand rapidly enough to protect you even when you were not belted in, then children in the front seat might be hurt. They deliberately did not mention this fact to Congress, in fear that the air bag law might not be pass. They just admitted the week of May 16 that the air bags cause more damage to front-seat passengers and drivers who are belted-in rather than those who are not. Why believe ANY government reports or recommendations unless you can study the basic data from which the recommendations were derived?

Apropos of poor math training, tonight we attempted to give our waitress the check with a coupon good for an $25 discount, and asked her to divide the bill into 2/3 and 1/3 with tax and tip. It took her only 20 minutes (!). Hooray for the new math.

What I am saying again is that correlation is not causation, and we can only hope that the low salt diet will be of benefit to some patients, and not too harmful to others.

BTW, if you have a blood pressure problem, please make sure your doctor measures the blood pressure in both arms.

Saturday, April 17, 2010

Obamacare, Medical Economics, Gov't Guidelines

This blog is an attempt by a family physician to evaluate "Obamacare" from the perspective of a patient, since the bill will affect them the most. To begin with, the same arguments made today against "Obamacare" were made 35 years ago against Medicare, and by the same groups. Almost all of my MCR patients today are more than satisfied with the system, and their children are even more so, since they can spend their money on their children's college education instead of on their parents' medical bills.

The first modern government to start government medical insurance as well as social security and workmen's compensation was that of Prussia under Otto von Bismarck in 1887 (cf. "Blood and Iron"), because he felt that a socially secure worker was a better worker. The first state government to mandate health care was Massachusetts. I don't yet know how it is working out, except that there is always a dearth of primary care physicians, since diagnosis and thinking through are not well-compensated. I think that it is wonderful that the parents' coverage of their children will be extended to age 26, since fewer newly-minted college graduates are getting immediate jobs.

Initially, the plan will cost more than is predicted, because fewer people will die. This was discovered when MCR covered dialysis in all ESRD patients. Without dialysis, many patients died of their renal disease. With dialysis, many lived longer lives, and therefore cost the system more.

I also envision that with state-controlled insurance, you won't have to go scurrying to find a new internist, gynecologist and pediatrician just because your employer changed medical insurance companies.

The one economic calculation that is never done, however, is how much living people contribute to government finances. If you dropped dead from a heart atack now, then that is the end. If they call 911, do CRP, rush you to the hospital and do emergency CABG surgery, the economists say that you cost the system $30,00 in medical expenses. No one adds that now you will work and pay taxes for another 20 years, and yourtaxes will amount to much more than $30,000.

Medical economics is also unpredictable: I bought a lot of Pfizer and Merck stock years ago, because they had the largest and most aggressive sales force. I reasoned that the more drugs people bought, the longer they lived, and the longer they lived, the more drugs they bought, so drug stocks should rise forever. When the drug stocks flattened out for 2 years, I realized that the market made no sense to me, and got totally out.

We will also spend less on acute medical care if everyone has his/her own doctor, because workups of medical problems in the emergency room is enormously expensive, while your family doctor who knows you can diagnose your problem with much fewer tests (e.g. he will not order a CT scan of yuor brain for ordinary dizziness).

BTW, the best way to diminish medical malpractice suits is to eliminate contingency fees. This law could be passed by any state legislature. At the same time, perhaps we should eliminate medical class action suits as well. Dow went bankrupt because a Texas jury was convinced of the "fact" that leaking silicone breast implants caused chemical lupus in susceptible females. Of course the fact that an article in NEJM demonstrated 2 years later that the association was not one of cause-and-effect did nothing to reverse Dow's financial position.

We should be very cautious about following any government guidelines for medical treatment. As I have stated before, it is very unlikely that a panel of 20 physicians agree 100% on anything, but unlike the arguments about global warming, we never get to see a minority report. The "normal" value of glucose and of cholesterol keep on being lowered, although statins seem to benefit everyone regardless of their cholesterol level, and intense control of diabetes seems to benefit few, if any (but if you are over the limit it does raise your life insurance premium). The suggestion that mammograms do not benefit women in their 40's was met with a storm of protest. A Nobel prize in medicine was given to the doctor who "proved" that pre-frontal lobotomies cured schizophrenia.The drug Singulair came out 2 months after the guidelines for asthma treatment were published. The only pro/con discussion about benefits or lack thereof of lowering salt in the diet was published in Lancet more than 10 years ago. The government knows that moderate use of alcohol reduces heart attack risk, but they still don't recommend starting. No patient is "average", and every patient is "special", best known by his family doctor, and we are spending too much time excplaining to insurance companies and Medicare Part D that in this particular patient the generic drug does not work as well as the brand name does.

The overall economic picture is that medical care saves lives, technology works but gets increasingly more expensive, and we wil end up rationing by time, availability, or money