Interesting epi abstract of the week
Courtesy of your friends at the American Journal of Epidemiology.

[No comment from me, since I know nothing about this area of research. But I couldn't resist posting this.]

Association of Body Mass Index with Suicide Mortality: A Prospective Cohort Study of More than One Million Men

Patrik K. E. Magnusson 1, Finn Rasmussen 2,3, Debbie A. Lawlor 4, Per Tynelius 2,3 and David Gunnell 4

1 Department of Genetics and Pathology, Uppsala University, Uppsala, Sweden
2 Child and Adolescent Public Health Epidemiology Group, Department of Public Health Sciences, Karolinska Institute, Stockholm, Sweden
3 Division of Epidemiology, Stockholm Centre of Public Health, Stockholm, Sweden
4 Department of Social Medicine, University of Bristol, Bristol, United Kingdom

The authors investigated the association of body mass index (BMI) with suicide in a record linkage study based on the Swedish Military Service Conscription Register, the Population and Housing Censuses, and the Cause of Death Register. The cohort studied consisted of 1,299,177 Swedish men who were conscripted in 1968–1999, had their BMI measured at age 18–19 years, and were followed up for as long as 31 years. A strong inverse association was found between BMI and suicide. For each 5-kg/m2 increase in BMI, the risk of suicide decreased by 15% (95% confidence interval: 9, 21). The association was similar when subjects with mental disorder at baseline were excluded from the analysis. BMI-suicide associations were similar in relation to suicide deaths occurring in the first 5 years of follow-up (hazard ratio for each 5-kg/m2 increase in BMI = 0.84, 95% confidence interval: 0.73, 0.96) compared with associations 10 years after baseline (hazard ratio = 0.87, 95% confidence interval: 0.79, 0.96), indicating that weight loss as a consequence of mental illness does not explain the BMI-suicide association and that factors influencing BMI may be causally implicated in the etiology of mental disorders leading to suicide.

Testing, testing

Amanda Schaffer, who is smart and writes well (and is apparently an M.D., not that this is necessarily a contradiction) says what every epidemiologist has been thinking about one of today's medical trends: over-screening for a host of maladies. One thing she doesn't discuss in detail, though she does mention it, is the controversy over prostate-cancer screening and PSA.

Over at the New Yorker, Dan Baum's article "The Price of Valor" [not available on-line] examines the mental price paid by soldiers for doing their job: killing the enemy. He convincingly shows the need for a thorough study of psychological problems due to killing enemy combatants, and, in a feat of terminological avoidance, he does it all without once using the word epidemiology.

One comment on the article. Baum cites figures showing that the rate of suicide among active-duty servicemen is lower than among the general population, and ascribes this to the fact that "it's difficult for a soldier to be a loner" (I'm paraphrasing). I think this difference is more likely due to something epidemiologists call the healthy worker effect (HWE) -- people with a steady job tend to have lower rates of most diseases than do the (non-employed) general population, because the chronically ill and disabled tend to be screened out of the employment pool. The same is even more true of soldiers.

This raises some interesting questions about psychological sequelae among active-duty servicemen, and whether there is an HWE for mental health among those in the military. Hey, that's a journal-club topic. (I don't mean this, though it seems interesting.)