Two child specialists issue a timely reminder in the December 22 issue of the British Medical Journal . Indianpolis-based Rachel C Vreeman, a fellow in children's health services research, and Aaron E Carroll, an assistant professor of pediatrics, remind physicians not to be taken in by myths perpetuated in medical science:
Physicians understand that practicing good medicine requires the constant acquisition of new knowledge, though they often assume their existing medical beliefs do not need re-examination. ...
Even physicians sometimes believe medical myths contradicted by scientific evidence.
The prevalence and endorsement of simple medical myths point to the need to continue to question what other falsehoods physicians endorse.
Examining why we believe myths and using evidence to dispel false beliefs can move us closer to evidence based practice.
Let's face it, doctors are busy people. Reading all the latest journals -- and, particularly, the methods sections that often contain the key statistical manipulations -- is a virtually insurmountable task for GPs or area specialists like those serving our children. Take, for example, an aricle on salt and blood pressure in children published in the Journal of Human Hypertension in September 2007 by anti-salt war chief Graham MacGregor and his associates. MacGregor et al reported that
An increase of 1g/day in salt intake was related to an increase of 0.4 mm Hg in systolic and 0.6 mm Hg in pulse pressure....The consistent finding of our present analysis of a random sample of free-living indiviudals with that from controlled salt reduction trials provides further support for a reduction in salt intake in children and adolescents.
That's the item that may have caught readers' attention and, if so, it would have perpetuated another myth -- that salt was important to the blood pressure of children. Don't blame the journal, however; the editors commissioned an editorial to attempt to keep the story straight -- and they continue to make that editorial available as their top-listed Featured Article. In that corrective editorial , fomer International Society of Hypertension president Michael H. Alderman explains:
Specifically, a difference in salt intake of 1 g was associated with a 0.4 mm Hg rise in blood pressure. However, the significance of this relationship disappeared after correction for energy intake. ...
Regrettably, the current report provides little information regarding other associations to blood pressure or variations in other characteristics that might be associated with variations in sodium intake. For example, stature and physical maturation are associated with blood pressure. Bigger children may be muscular or pudgy. Children who exercise vigorously may have large energy (and sodium) intakes, and be taller and leaner than youngsters who have the same body mass index and different life styles. Cooper et al. postulated that the strong link of creatinine to blood pressure might reflect muscle mass and perhaps be a marker of body size. This, in turn, might be the most powerful determinant of blood pressure in children-more important than age or sodium. Perhaps, the best measure of growth and development available here is mid-arm circumference. The strong arm to blood pressure correlation may reflect muscle mass and suggests that diets high in energy (and therefore, among other things, sodium) may be conducive to physical maturation, along with a slightly higher blood pressure. In short, if this were the causal pathway, then higher pressure might even be a desirable sign in children.
Dietary intake is complex, and to characterize it on the basis of one element may well oversimplify any assessment of its value. For example, given the high correlation of energy with virtually all other nutrients, it is possible that those consuming more sodium (and energy) had more satisfactory consumption of other important dietary elements-both known and unknown. In any event, blood pressure is not the only measure of the health of children. The British Survey of Young People probably includes, in addition to physical and physiological data, information on other social, economic and developmental characteristics whose explanation might well inform our understanding of the relation of blood pressure, diet, health and development in these youngsters. Of note, He et al. also provide some other interesting information. For example, they note that 18-year-old British residents, in 1997, were consuming 2.6-g of sodium per day. That was similar to levels found in Chicago a decade earlier, and falls within the range of adult sodium intake seen world-wide in most countries and suggests that, a decade and 2 ago, these near adults were within that range.
It is also interesting to note that measures of discretionary sodium use did not correlate with blood pressure. This supports the Cochrane Collaboration conclusion that there was not sufficient evidence for a general dietary recommendation to reduce sodium intake. (emphasis added)
Medical myths can cause real damage. With regard to children, it seems that once corrected for caloric intake, there is no association of blood pressure and salt intake, but there IS a strong association of calories (and salt) with healthy development of children. Perhaps the biggest myth is that diet is less important than its component nutrients. Don't let your pediatrician get duped or pass on medical mythology.
Or should we title this: "Get government out of the bedroom ... and the kitchen"?
Don't miss the "Brave New Diet" op ed piece by Sally C. Pipes in today's Washington Post . To give you a flavor, she points out that basketball superstar Kobe Bryant and undefeated New England Patriot's QB Tom Brady -- to say nothing of "Hollywood hearttrobs" Brad Pitt, Matt Damon, Tom Cruise and George Clooney" -- are all "fatties." They're overweight using today's metrics. Besides some useful facts on government games-playing on the obesity issue, the political insight about dietary guidelines is particularly timely -- and planned -- for this holiday season with its parties and feasts. Ms. Pipes notes that
"underlying this ["common political refrain that America faces a childhood obesity epidemic"] is the premise that we're helpless before gingerbread cookies and honey-roasted hams -- unable to resist these and other foods and incapable of putting down our forks. We can be cured, it seems, only by government intervention such as the banning of trans-fats and sodas from public schools.
But is it the food, or is it us? Is it a proper role of government to tell us what we can or can't eat?
She poses some questions she'd like answered "[b]efore we let Uncle Sam into our kitchens, at school or at home" and concludes:
People make choices. And government should protect -- not restrict -- the freedom to make those choices so long as we're not harming others.
While we may not always like the choices others might make, it is essential that we all have the freedom to choose for ourselves. Once we accept the idea that the Nanny State should step in when it's "for our own good," we've taken a very big step down the road to something like the scene painted in George Orwell's "1984" -- when citizens wake each day to mandatory exercise classes on the Telescreen.
Most of us would prefer to choose for ourselves whether to exercise or have an extra helping of apple pie. And if we gain an extra pound over the holidays -- so what? That's why we have New Year's resolutions.
How can it be that Americans are living longer and healthier lives than ever before and yet dying in unprecedented numbers from chronic diseases? Are we confusing risks of proxy conditions for real risks of adverse health events?
Successful people live in the present, but they think seriously about the future. They invest themselves and their resources to make tomorrow better than today and to cushion the inevitable bumps in life's road. Through learned precept or harsh experience, they know that "an ounce of prevention is worth a pound of cure." They've also learned to count their blessings along the way, to temper their worry about the future by appreciating the good fortune they've enjoyed.
We use the same thought process to fashion public health policy. As a society, we have never been healthier nor longer-lived, yet these hard-won achievements are tempered with recognition that many amongst us and elsewhere in the world live Hobbesian lives. We recognize the fragility of our personal health and the imposing shadow of chronic disease in our lives and in our families. We invest ourselves, sometimes wisely, sometimes not, in quests to improve our diet and fitness and otherwise protect our health and that of our loved ones. We crave security in matters inherently uncertain. We sacrifice to prevent potential threats, often accepting taxes and social regimentation, believing that using a seatbelt or getting a flu shot is a reasonable trade-off against injuries in car crashes or a flu pandemic.
Just as we do as individuals, as a society we accept risk trade-offs, but we do it based on our belief that these risks have been fairly described. While each of us has a unique set of risk tolerances, the entire calculus is undermined if the information fed into this vast social "brain" is compromised by poorly-understood data limitations or manipulated by unseen parties with special interest bias.
Not to say that these choices are easy. We are beset, as individuals and citizens, with media coverage of emerging science which often seems conflicting. We hear blaring warnings about health threats and advocates' impassioned appeals for action on divergent strategies based on different diagnoses. It's confusing.
Take, for example, two recent "authoritative" pronouncements. In the new publication from the Department of Health and Human Services (HHS), Health, United States, 2007, a compendium of more than 150 tables reporting data from the Centers for Disease Control and Prevention, as we reported earlier :
Life expectancy is at an all-time high. Females live longer than males, but a baby born in 1900 would live until 1948 (men) or 1951 (women) -- 48 and 51 years, respectively. Boomers born in 1950 will live, on average until 2015 (men) or 2021 (women) -- 65.5 and 71 years, respectively). The new report predicts children born in 2004 will live until 2079 (men) and 2084 (women) -- 75.2 and 80.4 years respectively. We take it for granted, but it's big news. And good news.
Children are healthier. In just the past quarter century, the number of children who died before age 14 has been cut in half -- in half! (since the mid-20th century, the rate has been cut 80%). Youth and teens are 60% less likely to be in "fair" or "poor" health. Almost as good as Ivory Soap, 98.2% of our children are healthy.
Adults are thriving, too. Despite our aging population, the percentage of all people in "fair" or "poor" health has dropped in a decade by more than 10% -- from 10.4% in 1991 to 9.2% in 2005. Physical limitations have also been dropping, from 13.3% to 11.7% over the past eight years while age-adjusted vision- and hearing-impairment, over the same period, have improved a remarkable 65% (dropping from 10% to 3.5%).
Mortality continues to decline. The new figures confirm those we reported earlier this year in comparing the U.S. with Americans' steady salt intakes with mortality figures in Finland which compromised its health improvements as it reduced its population's salt intake. Overall, age-adjusted mortality for all of the leading causes of death are in decline -- cut in half since 1950. In just the past 14 years, deaths from the leading cause, heart disease, have dropped by a third. Deaths from the second-leading cause, cancer, have fallen 14% and the third, stroke, by a whopping 72% (with no reduction in dietary salt). The key is age-adjusting. If we don't die of something in our youth or early adulthood, we reach old age where we (all, eventually) die of "old age" ailments like respiratory infections or Alzheimers's. In fact, the biggest risk of dying is getting old.
But, just as we were feeling that perhaps all the doom and gloom of rising health costs and millions without health insurance, was a manageable challenge, The Partnership to Fight Chronic Disease, a new national coalition of business and labor groups, issued its "Policy Platform" declaring that "rising rates of chronic health problems pose a significant and unsustainable burden on the U.S. health care system" and called for Americans to display "a willingness to enact policies that help Americans better prevent and manage chronic illnesses." The Platform calls on the presidential candidates to "highlight common-sense reforms." Pointing out that 77% of U.S. healthcare costs are due to chronic disease, it cites (other) CDC figures showing two-thirds of American children will develop diabetes leading to "lower life expectancy than their parents." Scary stuff. The Platform throws around a lot of numbers, too, such as alleging that obesity costs society $200 billion a year.
Head-scratching time. What about the other CDC figures that show that overweight Americans are actually healthier than their thinner fellow-citizens ( 1 2 3 4 )? You may remember: the ones CDC issued as revisions to their earlier obesity alert .
Now, let's accept that the people making these analyses are most likely fair-minded advocates for their views. The first thought in sorting this out is the correct one: consult the data; a close reading of the studies may help explain the discrepancies and where the authors of various studies may have claimed more than their data show. There is another possibility, however.
While there is general consensus that preventing cancer or heart disease is better - and likely less expensive - than caring for the victim after a malignant tumor is discovered or a heart attack occurs, the differing statistical worldviews as described in Health, United States, 2007 and the PFCD Platform may come down to how risk is defined.
Take the seat belt example. Unrestrained car drivers and passengers are clearly at greater risk of injury or death than those who "buckle up for safety." We'd never, knowingly, combine the two groups to determine the average risk when the documentation of the very different risk profiles is available.
Transfer that thinking to the question of the risk of high blood pressure. About 20% of Americans have high blood pressure, hypertension. And hypertension is responsible for about 16% of heart disease. The 20% with high blood pressure include, of course, those whose current blood pressure exceeds the defined minimum 140/90 mmHg. But the calculation also includes all those whose blood pressure would have been at the "hypertension" threshold except that they took medications or made lifestyle adjustments to lower their blood pressure. Those who managed their blood pressure (like those with seat belts), surely have a lower risk. Unlike the seat belt example, however, they are all lumped together: "once a hypertensive, always a hypertensive." The group that modified its blood pressure should be considered a separate, lower-risk group. By lumping them together, we inflate the number of people identified at risk and targeted for public health concern.
Better data would, thus, help us understand why we continue to have a large number of people with hypertension while at the same time we have achieved fantastic reductions in the rate of heart disease. Hypertension is often "sold" as a disease when it is, rather, an indicator, a marker, an intermediate variable. We are concerned about heart attacks, strokes and mortality. When it comes to treating this surrogate marker, we must never lose track of the real objective: improving health outcomes, not modifying "risk factors" - especially one that explains only one-sixth of the problem. The body is complex and its systems, redundant and interconnected. Simple solutions may make great headlines, but they don't change the "medical facts of life."
So, as we marshal our resources and prioritize our public health targets, let's keep in mind that efforts to prevent chronic disease must be assigned using real-world data. We can prevent high blood pressure, but if the side-effects (e.g. increased insulin resistance, elevated plasma renin activity, etc.) impose unanticipated costs, we need to prevent heart attacks using the best weapons we have. And those weapons are proven. They include medications. They may include lifestyle interventions like weight control and fitness. They don't include salt reduction for the general population.
The Food and Drug Administration recently asked for comments on what new reference values the agency might use to calculate the percent daily value (DV) on the Nutrition Facts and Supplement Facts labels and what factors the agency should consider in establishing such new reference values. The Salt Institute provided a comprehensive response addressing the questionable value of this type of labeling to consumers.
The Salt Institute strongly support the provision of objective scientific information to consumers in a manner that will help consumers can make informed choices. Currently, nutrients are labeled in isolation - not in reference to thief role in the whole diet. While placing the impact of individual nutrients into context with our "whole diet" is a complicated task, this is how nutrients are metabolized on an ongoing basis. Lacking a complete knowledge of how individual nutrients impact upon each other in the overall diet, the question remains as to whether the consideration of nutrients in isolation for the purposes of informing consumers is truly a functional benefit to them. While no one doubts that this data provides information, it can compromise perspective by taking nutrients out of their 'holistic diet' context.
Based upon the results of the DASH diet and the most recent results on the positive impact of vegetables on the diet, we are not certain that the establishment and dissemination of a DV is of particular benefit to consumers. Salt consumption is self limiting because of taste and despite the outcry regarding our current levels of consumption, our cardiovascular performance is significantly better than that of Finland - the only country that has significantly reduced its salt consumption by 40-50% in the last 30 years. If a DV is felt to be absolutely necessary, it is certainly not in anyone's interest to reduce it any further than its current level.
The news media's been reporting a paper in The Lancet this past week that purports to "prove" that salt produces chronic disease mortality, killing 8.5 million persons around the world. As the headline writers penned, that would be a serious condition, indeed, if it were true. But a closer look shows the authors engaged in the same statistical sleight-of-hand that was on display at the FDA hearing a couple weeks ago.
No matter how you quantify the enormous costs associated with chronic disease and, in this case, heart disease, the key to assessing the veracity of the numbers associated with salt is the linkage. Simply put, there is none. It's manufactured -- it exists only as the product of a mathematical model that assumed that lower salt diets WILL lower population blood pressure AND that lowering BP in this way WILL produce the lower incidence of CV death. GIGO's the term for it; garbage in, garbage out.
In fact, the authors cite one of two studies of salt reduction in Finland. The study they don't report is the health outcomes of Finand over the year it reduced its citzens' salt intake. Absent any control, the numbers show improvement, but compared with other countries over the years, Finland lagged behind those countries that did NOT reduce salt .
That The Lancet would choose to publish this reflects the policy preference on the author, not a substantive contribution to public health nutrition policy.