Risk Factors: More Risky Than You Might Think

Here’s a cynical proposition: Risk factors do a much better job of selling drugs and diagnostic tests than preventing diseases. But, let’s take this back a few steps. First of all, what is a “risk factor”? One of the better definitions has it: A characteristic, condition, or behavior, such as high blood pressure or smoking, that increases the possibility of disease or injury.

But even this definition could be improved. Properly understood, risk factors are associated with the increased possibility of disease or injury. After all, correlation is not causation! The term was first used in the late 1940s, likely stemming from the Framingham Heart Study in which such factors as cigarette smoking, elevated blood cholesterol, and high blood pressure were said to be predictors of one’s likelihood of dying from heart disease.

Again, though, we must step back. Physician Edward Jenner (1749–1823) is justly famous for turning the observation that milkmaids seldom got smallpox into the practice of inoculating patients to render them immune to the disease. Here was a negative risk factor that led to the eventual eradication of a once dreaded disease, even if Jenner did not use that term.

It would not be until the 1950s that any risk factor finding even remotely as good as Jenner’s would appear. That, of course, was primarily the work of another Englishman—Richard Doll (1912-2005), who documented the extreme correlation of cigarette smoking with lung cancer. It is estimated that 90 percent of all cases of lung cancer are caused by smoking, or to be more precise, occur in individuals who have smoked.

No chemical agent or lifestyle factor has ever come anywhere near such correlation with a disease, and it is quite doubtful that another ever will. But that doesn’t stop people from constantly proclaiming such correlations—touting them as would-be risk factors—virtually nonstop. Sadly, the “science” behind most of these pronouncements—and it matters not how esteemed the source—is questionable at best.

Yet, go to any major health website to read up on any significant disease, and you will surely find the risk factors. One of the more well-known is that being obese is a big risk factor for type 2 diabetes. As mentioned last week, someone came up with the figure that 80 percent of type 2′s are overweight. OK, let’s do the math.

According to the American Diabetes Association, 25.8 million children and adults in the US have diabetes, and this number includes 7 million who are undiagnosed (how does that work?). 90-95% of these have type 2, so that puts it at 24.5 million cases of type 2 diabetes. And, if 80% of these folks are overweight, that gives us 19.6 million corpulent type 2′s.

Now, how many people in the US are obese? We are told that 35.7% of adults fit this qualification, so let’s just apply it to a total population of 314 million. That gives us 112.1 million, of which 19.6 million are type 2′s.

Thus, our big risk factor correlating being overweight with type 2 diabetes proves out at a measly 17.5 percent, and that’s with all best case scenario assumptions in play. In reality, it could be much lower. Compare this to the 90 percent figure for smoking and lung cancer. Bear in mind that outside of smoking/lung cancer, the obesity/type 2 diabetes connection is the most highly publicized risk factor in public health.

With hundreds of fear-inducing risk factors extant, patients flock to all sorts of recommended diagnostics, and take many drugs whose sole purpose is to adjust blood titer numbers, indicative of a so-called risk factor.

Drs. H. Gilbert Welch, Lisa Schwartz, and Steve Woloshin collaborated on the 2011 book Overdiagnosed: Making People Sick in the Pursuit of Health. Following the book launch, Welch was interviewed by Lisa Chedekel of BU Today, and offered these remarks:

A lot of people [benefit from overdiagnosis]: Pharma, device manufacturers, imaging centers, and even your local hospital. The easiest way to make money isn’t to build a better drug or device—it’s to expand the market for existing drugs and devices by expanding the indication to include more patients. Similarly, for hospitals, the easiest way to make money isn’t to deliver better care; it’s to recruit new patients—and screening is a great way to do this.

The poster child for the problem [of overdiagnosis and overtreatment] is prostate cancer screening: Twenty years ago, a “simple blood test” was introduced; 20 years later, over one million Americans had been treated for a cancer that was never going to bother them. The test was the PSA. It’s able to detect minute quantities of prostate-specific antigen—minute as in one-billionth of a gram. Turned out a lot of men had “abnormal” PSAs. Many were found to have microscopic cancers—far more than would ever suffer from prostate cancer. So they were overdiagnosed.

Does it matter? Absolutely. Most were treated with either radical surgery or radiation. Roughly a third suffered side effects of treatment—generally related to bowel, bladder, or sexual function. And a few have died from it.

Sounds risky to me.

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25 responses to “Risk Factors: More Risky Than You Might Think

  1. “Thus, our big risk factor correlating being overweight with type 2 diabetes proves out at a measly 17.5 percent, and that’s with all best case scenario assumptions in play.”

    Or it proves the government’s “35.7% of adults are obese” is stupid wrong.

  2. Michael: That’s known as “SWAG” in the vernacular. (Scientific Wild____ Guess)

  3. It’s probably a statistical (read magic) number derived from personal observations, anecdotal evidence at Thanksgiving dinner, and feelings. Can you compete with undiagnosed autism?

  4. a worthwhile effort on nailing down the problem of population studies/relative risk/ causation.

    However a minor quibble–the rate of a problem in the burdened population is not the key, it’s the difference in rates between the unexposed or unburdened and the control population.

    Doll showed a 10 percent risk of lung cancer in smokers, a high rate of smoking i lung cancer patients, but the killer finding was a 900 percent increase in the rate of lung cancer in smokers.

    that’s enough to wipe out known and unknown confounders.

    as for the relative rates of DM type 2 in fat people, the rate of diabetes in fat people compared to non fat people is the killer comparison–adn no doubt you would have to ask–well what is it and how does it get compared adn whats a level where causation can be argued.

    the rate where causation can be asserted is minimum 100 percent increase in rate–Relative Risk of 2, but most epidemiologists ask for a 200 or more percent increase in rate over the control group of people who are not fat.

    to review the numbers Relative risk for fat people getting DM compared to general population is 19/112 as compared to 5/202 that’s 16.9% compared to 2.4 % that equals a Relative risk of 6.6.

    Now i am not commenting on the rates of missed diagnosis or the tendency to over diagnose diabetes, but i can tell you the stand alone Relative Risk of 6.6 is pretty strong for asserting causation.

    Glucose intolerance of the type II variety is due to metabolic inability of the insulin supply to control the glucose absorption/metabolism so the plausibility factor also is present–it’s not like we have no idea why fat people are more glucose intolerant–they are.

    John Dale Dunn MD JD emergency physician–not an endocrinologist–but i am interested in epidemiological rules for proof of causation and i did stay at a Holiday Inn Express in 2010, or maybe i just stole some breakfast when i was there to see a friend.

    • @John–

      Points all well taken, but consider that these popular risk factors are intended to scare people into changing their behavior–supposedly for better health. I left out the rather astounding finding that in the fattest group of people on earth (Sumo wrestlers) almost NONE are diabetic.

      The junk science aspect of all this, is that we are overstating the number of obese and the number of so-called diabetics, whereby the definition went down from 160 mg/dL to 126 mg/dL over less than a generation. More than that, all those terrible things that can happen to diabetics (now that 1′s and 2′s are sneakily grouped together) are also vastly, vastly overstated. Check out the “landmark” papers that all the clones–led by Silvio Inzucchi–love to quote from, conveniently leaving out the actual data.

      it will blow your mind how de minimis the differences between normals and type 2′s really are, with respect to retinal and neuropathy issues.

      • again, shaw, good points and insights on the nature of professiionals to promote themselves and their craft.

        medicalize everything and there will be rewards to the medical providers.

        the whole business of eating well and living well givers nannies a nose under the tent to tell people how to live. they like that.

  5. GoneWithTheWind

    Obesity is genetic. Not simply being overweight or a little over normal on the BMI scale but true obesity is genetic. Some races/cultures/countries are more obese then others. It is more prevalent in races and countries where their population more recently moved from a hunter gatherer to a consumer of food farmed/raised by modern methods. The paleo or hunter gatherer lifestyle is easier to survive if your genes are making you store food/fat. Hence people recently from this culture have higher rates of obesity.

    Diabetes enjoys a similar relationship in that it is genetic and the hunter gatherer diet allows diabetics to survive longer without obvious symptoms or early death. But once modern food practices are introduced to their lifestyle diabetes symptoms show up earlier and are more severe. Contrary to obesity which helped survival rates for hunter gatherers, diabetes merely was moderated by the paleo diet allowing individual to procreate and the genes to be carried to the next generation.

    Given this historic diet based connection it is logical that indeed whole races of people and cultures would be likely to produce obese people who also were diabetic if their culture were more recently from a hunter gatherer existence. Numerous examples of this can be found; the native Americans, Mexicans, South and Centtral Americans, African tribes, South Pacific Islanders, etc. This diet relationship is also responsible for the belief that it is the diet that “causes” obesity AND diabetes. But it is not.

    • @Gone–

      Interesting. So, in the long run, we’re all screwed.

      • GoneWithTheWind

        Well, no. Just choose your parents carefully. But on the other hand we all will indeed die from something. The trick is to die as late in your life as possible and to enjoy life as much as possible. But if your point is that we are prisoners of our genes I will only disagree in that I think that genes can predict a range of results. That is you might be overweight but you can indeed decrease or increase your weight with some effort and diet. Or you may have parents with high blood pressure but you can take steps throughout your life to reduce your blood pressure thus enjoying longer life and less risk. But in the end we all play the hand we are dealt and it is yours to play. The question is are you playing it or sitting out the game. What risks are you ignoring and can they be mitigated. A very difficult question in most cases made even more difficult because of the misinformation that is out there and often presented in a very seductive way.

        • @Gone–

          Thus, we come full circle. Should we consider risk factors or not? My take is that it is overwhelmingly simplistic hype. Why? Because all medical history is primarily based on self-assessments (until things get acute and become better documented).

          Thus, you need to have a blindingly obvious thing like smoking/lung cancer to achieve a finding worth worrying about. And, don’t even get me started regarding the side effects from titer-controlling drugs that are worse than the diseases they supposedly prevent.

          Does heart disease “run in my family” because my grandparents who smoked like chimneys died from it?

          Junk science, baby.

    • “Obesity is genetic.”

      Any third grader can tell you obesity comes from eating too much.

  6. A1C is a test for average glucose level over a period of several weeks or months. Since exponential decay is involved, the shorter period is less inaccurate. Us type 2 patients were told the disease was under control if our A1C score was 7.0 or less. In the last few years, the signs at a nationally respected hospital were changed from 7.0 to 6.5.

    • risk factors are crutches for medical people and ubiquitous–risk factors for heart disease are associations of varying strength–so if you ask a group of medical people whats the lifetime risk of cancer of the lung for smokers they will invariably peg it way too high.

      same with smoking and heart disease.

      risk ractors of 5 % percent range Relative Risk 1.05, de minimus, still get cosidered in evalautons and public health.

    • nannies always are working toward perfections and that means more intervention.

      reducing your risk? maybe

  7. Shaw, you made a conceptual mathematics error that undermines your whole paper

    You compared 90% of lung cancers occur in smokers to 17.6% of obese people have diabetes. The proper comparison is the 90% to 80% of diabetics are obese. You could also find the fraction of smokers who get lung cancer and calculate it that way. However, as it is, your thesis is based around apples to oranges.

    • @Ben–

      Comparison was not meant to be rigorous. Rather, the point was that risk factors are overblown. Besides, there are not reliable figures either on who is “obese” and who has diabetes—compared to lung cancer victims and their medical histories.

      The 80% figure on obese type 2′s is probably made up. I have searched in vain for a source for that for years.

      More than that, over-treating people (read statins, PSA-based modalties, etc) causes far more harm than good.

  8. GoneWithTheWind

    “Any third grader can tell you obesity comes from eating too much.”
    Indeed! But with more education you might discover that some people can eat as much as they want and literally eat massive amounts of food and stay thin while those with a genetic predisposition to obesity can diet their entire life and never achieve a normal or near normal weight. Please set your sights beyond third grade education.

  9. Life is a 100% risk of death.. ;)

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