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I’m always amazed at how the lipid hypothesis of heart disease has wormed its way deep into the souls of physicians, scientists, and medical/nutritional writers the world over. The flimsiest piece of research appearing to confirm this entrenched bias is not only accepted uncritically (not by yours truly, of course), but is shouted from the rooftops by the likes of USA Today, the New York Times, Reuters, and other general publications.
Then along comes a study with some true value that, although published in a prestigious journal, is vigorously ignored. Such seems to be the fate of a tremendous piece of research appearing in the current issue of Diabetes Care. Since this journal, like JAMA, makes available to the public the full text of articles its editors deem of significant public health importance, you can get the article in its entirety .
Researchers at University College in London looked at the mortality data generated over the past 33 years from the Whitehall Study, which, like the Women’s Health Initiative, is a large, government funded study. In the Whitehall Study
18,403 nonindustrial London-based male civil servants aged 40-64 years were examined between September 1967 and January 1970. In brief, measurements included height, weight, blood pressure, six-lead electrocardiogram, lung function (forced expiratory volume in 1 s and forced vital capacity), plasma cholesterol concentration, and a glucose tolerance test. A self-administered questionnaire was completed regarding employment grade, smoking habits, health status, and physical activity.
After an overnight fast the participants of this study underwent a glucose tolerance test in which they drank a preparation containing 50 grams of glucose. Two hours later they had their blood sugars measured. In a normal glucose tolerance test blood sugars typically return to normal within two hours after having consumed a glucose drink. The researchers wanted to record these 2-hr post glucose load figures and see how they correlated with mortality over the ensuing years.
The researchers divided the study participants according to their 2-hr blood glucose values into three groups. Those with 2-hr glucose levels below 95 mg/dl were considered normal; those who measured 96-199 mg/dl were deemed glucose intolerant; and those with 2-hr blood glucose levels at 200 mg/dl or greater were classified as diabetic.
As might be expected, after 33 years the diabetic group fared poorly compared to the normal and even the glucose intolerant group. Having a diabetic 2-hr post load glucose profile increased the odds of all-cause mortality by 2.37 and of death from coronary heart disease by 3.70. Clearly having an abnormal glucose tolerance test is bad news for prospects of a long life, much more so, in fact, than a “bad” cholesterol test.
But, the most interesting aspect of this study is what the researchers found in the normal group first at 10 years then at 33 years down the road. Everyone knows that a markedly elevated blood sugar level or a diabetic glucose tolerance test bodes poorly for long term mortality, but what about the lower end of the curve? Is there a difference there? Is there a difference in long term mortality between a blood glucose level of, say, 95 mg/dl and one of 85 mg/dl, both of which are considered normal.
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