The public health myths of cardiovascular disease prevention

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Like any political activity, public health advocacy must rely on the ordinary tools of political propaganda to advance its intended agenda.  Such is the case with public health proposals for the prevention of cardiovascular disease.  A critical examination of the topic exposes the blurred line between prevention and pretension.

The following characteristic subliminal message was reported last week in the heart.org (1):

Atlanta, GA – Deaths from heart disease in the US were at their lowest rate ever in 2006, down 5.5% on the previous year, according to preliminary figures from the Centers for Disease Control and Prevention (CDC). Nevertheless, it still remains the leading cause of death, say Dr Melonie P Heron (Division of Vital Statistics, CDC, Atlanta) and colleagues.

further adding:

With the exception of 1993, heart-disease mortality has shown a consistent downward trend since 1980, they note.

HALF-TRUTHS ON A SLIPPERY SLOPE

It is of course true that heart disease mortality has shown a “consistent downward trend since 1980.” But the fully disclosed facts date the actual onset of the monotonous decline to three decades earlier. The chart below is taken from an article in the Center for Disease Control’s Morbidity and Mortality Weekly Report curiously entitled “Achievements in Public Health, 1900-1999: Decline in Deaths from Heart Disease and Stroke, United States 1900-1999 (2)”

Click to enlarge

The arrogation of success is not subtle since in the years preceding the 1950 peak, public health policy was almost entirely directed at infectious disease control and not at all at heart disease prevention.  More remarkably, it can be seen that stroke mortality has followed a steady and unperturbed downward course for the entire century, seemingly unaware of our determined eradication efforts.

In the specific case of coronary heart disease, mortality peaked no later than 1968, before large scale public health activities aimed at reducing coronary risk factors were launched (*), and has been on a downward course ever since.

But the notion that the decline in cardiac mortality is a more recent phenomenon is often insinuated in press releases and at fund raising events, providing a plausible temporal relationship between the touted activities and the diminishing death rate.  Thus at a recent gala for the aptly-named “Heart Truth” campaign, we are told that:

NHLBI experts analyzed preliminary data for 2004, the most recent year for which data are available. This analysis showed that the last few years in particular have seen a steady decline in the number of heart disease deaths in women — deaths have gone down in each of the five years from 2000 to 2004, a consecutive yearly decline which has not occurred before,

prompting Ms. Laura Bush to comment: “The good news announced today shows that The Heart Truth awareness campaign is helping. (3)” The data, of course, refer to crude mortality.  When the more relevant age-adjusted numbers are examined in the National Heart Lung and Blood Institute (NHLBI)’s own chart book (4), the steady decline in coronary mortality for women shows no inflection point and has paralleled that for men for more than 30 years.

CUM(PUTER) HOC ERGO PROPTER HOC

But contriving temporal associations between policy and progress is not sufficient, of course.  Nowadays, epidemiologists turned health policy advocates eagerly follow the lead of climatologists and rely on “sophisticated” and “robust” mathematical modeling to “determine” the extent of benefit of public health activities (5).

One such study recently published by CDC investigators in the New England Journal of Medicine was modestly entitled “Explaining the Decrease in U.S. Deaths from Coronary Disease, 1980-2000. (6)”  The description of the methodology occupies a 40-page document only available as a supplementary appendix online.  Needless to say, the assumptions entered in the mathematical model are not few.  But applying the “validated” statistical technique to available epidemiological data the authors conclude:

The burden of coronary heart disease in the United States remains enormous, even though associated mortality rates fell by more than 40% between 1980 and 2000.  These two decades saw rapid growth in costly medical technology and pharmaceutical treatments for coronary heart disease, as well as substantial public health efforts to reduce the prevalence of major cardiovascular risk factors. Establishing the relative contributions of these two approaches is therefore of considerable importance.  We found that reductions in major risk factors probably accounted for approximately half the decrease in deaths from coronary heart disease, as in most other industrialized countries studied.

That reducing risk factors diminishes cardiac mortality is almost certainly true.  But since the reduction in risk factors almost routinely necessitates the use of “costly…pharmaceutical treatments,” meaning ordinary medical care, it takes a certain leap of faith to attribute the benefit to “public health efforts.”  But the authors’ intention of “actively promoting population-based prevention by reducing risk factors,” meaning more directives, targets, or guidelines issued by the CDC, however, is clear.  Meanwhile, the most carefully conducted field study of coronary event rates (7), also reported in the New England Journal of Medicine, showed that while coronary mortality did indeed decline between 1987 and 1994, the incidence of first myocardial infarctions was utterly unchanged, casting some doubt on the magnitude of the benefit derived from population-based risk factor modification and prompting a prominent NIH epidemiologist to briefly ponder on this oddity:

A more puzzling paradox is the fact that no decline in the incidence of myocardial infarction was observed in the ARIC sample during a period when the prevalence of causal risk factors was reduced (8).

AN EPIDEMIC OF PARADOX

So how do politicians respond when allegations are challenged by facts? A common way is by appeal to fear. In the same report from the heart.org we hear the comments from the American Heart Association:

AHA president Dr Timothy J Gardner told heartwire that the new figures were good news, but he warned against complacency: “The sustained decline in deaths from heart disease reflects a reduction in some risk factors, especially less smoking, plus more effective treatment of heart disease.”  But he added, “These gains will be reversed, however, if the epidemic of obesity and diabetes continues.  Today’s young people could become the first generation to face a shorter life expectancy than their parents.”

There is no need to speculate on how the good news could translate into dwindling support for the AHA.  But the obesity epidemic seems so far unwilling to fulfill its prophesied role of heart-breaker, and mounting evidence appears to indicate improved longevity and decreased rates of complication among the “overweight.”  Thus Uretsky et al. reported recently in the American Journal of Medicine:

…our analysis of the INVEST cohort suggests that among patients with a history of hypertension and coronary artery disease, overweight and class I to III obesity were associated with a decreased risk of morbidity and mortality compared with normal-weight patients, despite less blood pressure control. This finding is consistent with the notion of an “obesity paradox” that has been described in patients with documented cardiac disease (eg, heart failure), patients undergoing percutaneous coronary intervention, and patients with coronary artery disease referred for single photon emission computed tomography (9).

And as Sandy Szwarc reminds us in her excellent series on the topic, a paradox could just be a label applied when a simple fact challenges an orthodox opinion long promulgated on the basis of prejudice or without scientific circumspection (10).  In light of this we can only hope that the characteristic alarm-ism expressed in the name of public health will not backlash into an even deeper distrust of the medical profession by the public, hurting those physicians whose intention has always been to practice medicine one individual at a time.

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(*) The anti-smoking campaigns of the 1960’s were primarily directed at the prevention of lung cancer rather coronary disease. Ancel Keys and the diet-heart hypothesis were featured on the cover of Time magazine in 1961 but concerted dietary guidelines and campaigns aimed at reducing fat consumption were not organized until the 1970’s. The prevalence of hypertension seems to have actually increased between1960 and 1970.

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One thought on “The public health myths of cardiovascular disease prevention

  1. Also note the paradiox that this parallel decline in ischemic heart disease death rates in men and women occurred despite the fact that men initially had much higher rates of smoking, while women had much lower rates of quitting during this period.

    And here’s another: When the sharp decline in heart disease death rates began in the United States in the 1960s, it was the same in smokers as in non-smokers: “Nonsudden CHD death decreased by 64% (95% CI 50% to 74%, Ptrend<0.001), and SCD rates decreased by 49% (95% CI 28% to 64%, Ptrend<0.001). These trends were seen in men and women, in subjects with and without a prior history of CHD, and in smokers and nonsmokers.” (Temporal trends in coronary heart disease mortality and sudden cardiac death from 1950 to 1999: the Framingham Heart Study. CS Fox, JC Evans, MG Larson, WB Kannel, D Levy. Circulation 2004 Aug 3;110(5):522-527.) The decline in cigarette smoking has been much greater in middle-aged men than in middle-aged women, which is not at all in accord with the equivalence in the decline in mortality for the sexes. And the decline began before any significant number of smoking bans.

    http://circ.ahajournals.org/cgi/content/full/110/5/522

    For political reasons, the anti-smokers have suppressed the hypothesis that smokers and non-smokers have merely been exposed at different rates to the real causal factor(s), and that their respective rates of heart disease have declined as population-wide exposure declines. This is the hypothesis which best fits the evidence!

    For socioeconomic reasons, smokers and passive smokers are more likely to have been exposed to infectious causes of heart disease, such as cytomegalovirus. The anti-smokers’ studies deliberately ignore the role of infection, in order to falsely blame active smoking and secondhand smoke for the excess. This is the reason that the pretended effects of secondhand smoke are so similar to the pretended effects of active smoking.

    http://www.smokershistory.com/CMVHD.htm

    But here’s the best paradox of all – they claim that smoking bans supposedly cause “immediate, dramatic” declines in the number of heart attacks. In the Pueblo study, the death rates from acute myocardial infarction actually increased in the year after the ban, the same time they were boasting that the number of admissions declined! That suggests that people were dying because they weren’t admitted to hospitals when they should have been! And in the Indiana study, they exploited an anomalous spike in acute MIs during the “before” section of the study, to make the “after” part look better! And in the Helena study, the actual death rates from acute myocardial infarction (as opposed to hospital admissions which were the endpoint of the study) were nearly identical in 2001 (before the ban) and 2002 (the year of the ban), and reached their lowest point in 2003, the year after the smoking ban was repealed.

    http://www.smokershistory.com/etsheart.html