Thursday, July 23, 2009

Increasing autoimmune diseases?

This blog is usually about teen sex, but I'm also interested in the speculation that allergies and autoimmune diseases have increased in recent years, so sometimes I write about those.

A study published this month found evidence of such an increased prevalence of one autoimmune disease in a sample of men. They took old blood sampled from men at an Air Force base just after World War 2 (1948-1954) and used as a comparison group men currently at similar ages and men with similar date of birth. They tested the blood for two indicators of celiac disease, an autoimmune disease: tTGA, followed with a second test (EMA) in only the tTGA positive and weakly positive subjects. I presume that they know that these tests have similar rates of false negatives and false positives in 60 year old blood as in fresher blood.

They found more than 4-fold greater prevalence of celiac disease as judged by this test: 0.2% in the old blood and 0.9% and 0.8% in the new blood. Since the higher rates were found in the similar age comparison group, that finding provokes the question whether the subjects from the air base went on to develop celiac disease, but they don't have blood samples to answer that question.

I am curious whether this finding holds up in other large collections of old blood, (and also whether in 60 years their current samples of new blood test the same way.)

As a reader pointed out: the Air Force cohort was healthier than the contemporary young cohort due to having been pre-screened as part of their Air Force physicals. While this study's stated purpose is to be looking for asymptomatic celiac disease, there is of course a spectrum of non-specific symptoms, some of which may have caused the Air Force to screen people out and they would not have been screened out of the contemporary young cohort. It's too bad they don't have access to a contemporary Air Force cohort, though of course the Air Force standards might have changed over time. The only way to know whether this is a real effect is to repeat the study in different samples with different types of biases and vulnerabilities.

Since we don't know the reason for the higher prevalence of celiac today, the takeaway may be to live more like they did in the late 1940s including those swell hats and suits. If the increased prevalence is from the increased cleanliness we have now versus 60 years ago, use plain soap and toothpaste rather than the ones with antimicrobials and follow fewer food safety rules just as they did in the old days.

They also found that the 0.2% with presumably untreated celiac went on to die at 4 times the rate of the people without it; while they were dealing with small numbers, the mortality rate was at least twice the celiac negative (Hazard Ratio 3.9 with confidence interval (2.0, 7.5)), so this is important.

[Photo from Georgia Encyclopedia.]

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