By Dr. Geoffrey Modest
The CDC just released a somewhat encouraging report showing that newly diagnosed cases of diabetes in the US has started to decline (see overall graph below, and the various articles/subgroup analyses at http://www.cdc.gov/diabetes/statistics/incidence_national.htm ). A few observations:
- There seems to be an overall consistent trend to fewer cases since 2009, though the number of new cases is way above 1980 (the age-adjusted incidence in 1980 was about 3.5/1000 and in 2014 was 6.6/1000) and is basically the same as in 2004-5. Of note, the criteria for diagnosis of diabetes did change in 2010 to include the A1C>=6.5. No doubt this increased the number of diagnoses of diabetes, so the subsequent falloff may even be more significant.
- These data includes only those with diagnosed diabetes, and from current epidemiologic studies, it seems that about 25% of diabetics are currently unaware of their diagnosis
- The age-adjusted incidence of diagnosed diabetes has trended down for whites, blacks and hispanics, but was only significant for whites. Also, the overall incidence has consistently been much lower in whites (in 2014, was 6.4/1000, in 2009 was 8.0/1000) than blacks (was 8.4/1000 in 2014 and 11.5/1000 in 2009) and hispanics (was 8.5/1000 in 2014 and 11.9/1000 in 2009)
- The age-adjusted incidence of diagnosed diabetes has trended down for those with less than high-school education, those with high-school education and those with greater than high-school education, but was only significant for those with greater than high-school education. Also the overall incidence has consistently been much lower in those with greater than high-school education (in 2014, was 5.3/1000, in 2009 was 6.7/1000) than those with high-school education (was 7.8/1000 in 2014 and 9.0/1000 in 2009) and those with less than high-school education (was 11.1/1000 in 2014 and 15.4/1000 in 2009)
So, what does this all mean and how do we interpret it?
- Part of the issue may be that diabetes has a strong genetic component and some of the leveling off of new cases may be that the steep rise prior to 2008 reflected obesity/lifestyle issues in conjunction with genes, and we have perhaps reached the saturation point for the genetic component (i.e., those predisposed genetically to diabetes have largely already become diabetic)
- Part of the issue may be changes in obesity. Hard to compare CDC data over the past 20 years, since there was a change in CDC methodology in 2011, but it appears at least that obesity has plateaued and downtrended a bit in adolescents.
- Some really positive changes have been the decrease in soda consumption: over the past 20 years, there has been a >25% decrease in sales of full-calorie soda, with a “serious and sustained decline”. From 2004-12, children consumed 79% fewer sugar-sweetened beverage calories a day (4% cut in overall calories) — see http://www.nytimes.com/2015/10/04/upshot/soda-industry-struggles-as-consumer-tastes-change.html
- These changes seem to reflect public health initiatives to decrease soda consumption (since the changes are not related to increased taxes or other financial incentives)
- McDonalds, for the first time, is closing more stores than they are opening…
- More people are doing daily exercise than before
- Unfortunately, the CDC data really shows that the significant changes in new diabetes incidence pertains mostly to white and more-educated people. That being noted, I should add that my experience in a poor minority community is that there really have been pretty consistent improvements overall in lifestyle. I have many more patients who eat better (much less soda/more water for drinks, decreases in junk food) and much more consistently do exercise (mostly walking outside when the weather is nice, or climbing up and down stairs for 10-15 minutes when not. And some who ride bikes or have some home exercise machines, or go to gyms). This has been a pretty striking change over the past 10 years or so. I suspect part of the issue is that I have spent a long time discussing lifestyle changes with my patients over many years, but also (and perhaps more important) is that there has been more general awareness of the importance of eating well and exercising which i am supporting and reinforcing.
- Though, an important cautionary note. One concern I have raised in many past blogs is that we (scientists and physicians alike) often develop our models of disease based on what seem to be reasonable physiologic data, then generalize it and formalize it as recommendations. We always do this, and there really is no way around it. But we are often wrong. In the 1970s, it seemed reasonable to note that dietary fats are related to atherosclerotic disease (which was a particularly big killer then), and that some fats were worse than others (saturated fats seemed to be the worst then, though there were early data that trans fats were actually the worst by far and still took another 4 decades to be reduced/eliminated, polyusaturated were better but lowered HDL as well as LDL, then the best were monousaturates which raised HDL while lowering LDL). So, we endorsed a low-fat diet, which translated to a high-carb diet (e.g., low fat ice cream, etc., had fewer fats and more carbs). Many of us realized subsequently (though a lot of the data was available many years ago), that eggs really were not so bad in terms of clinical outcomes, and that the high glycemic/high carb diets may well have been the major factor propelling the obesity epidemic and diabetes. So, I think the take-home message here is that we will always be constucting biological/medical models (whether they be about dietary fat, homocysteine, postmenopausal estrogens, etc. etc.); that these models are natural for us to do and really important in determining policy (though best after the appropriate studies with important clinical outcomes are performed, but these often take many years to do, if done at all); but that we always need to be really vigilant in continually questioning the basis of these models through introspection and further studies, and not allowing a model such as the low-fat diet above to last for so long (I believe the goal is something like: do no harm….)
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