Saturday, December 31, 2005

More Piling On: Obesity Association with Injury Risk Equivocal

Am J Prev Med 2005;29(1): 41–45
Obesity and Risk of Nonfatal Unintentional Injuries

Huiyun Xiang, MD, MPH, PhD, Gary A. Smith, MD, DrPH, J. R. Wilkins III, BCE, DrPH,
Guanmin Chen, MD, PhD, Sarah Grim Hostetler, BA, Lorann Stallones, MPH, PhD

Background: Obesity is recognized as a risk factor for multiple chronic diseases. Yet, it is unclear whether
obesity is also associated with an increased risk of nonfatal unintentional injury.

Methods: A population-based survey was conducted among adults aged 18 years from January 1999
through October 2000. The relationship was investigated between body mass index (BMI),
defined as weight in kilograms divided by the square of the height in meters (kg/m2), and
risk of nonfatal unintentional injuries among 2575 respondents aged 20 years by
comparing percentage of adults between obese and nonobese respondents who had
injuries. Multivariate logistic regression further examined this relationship by controlling
for confounding demographics.

Results: A total of 370 respondents reported injuries in the previous year. We observed a linear
dose–response trend among women. An estimated 7.0% of underweight individuals (BMI
18.5) reported injuries. In contrast, 26.0% of men and 21.7% of women with a BMI 35.0
reported injuries. The odds ratio of injuries for individuals with a BMI 35.0 was 2.00 (95%
confidence interval1.07–3.74, p 0.05) after controlling for gender, age, education level,
marital status, family poverty status, and area of residence.

Conclusions: A marginally significant association between extreme obesity and elevated risk of injuries
was observed. Efforts to promote optimal body weight may reduce not only the risk of
chronic diseases but also the risk of unintentional injury among overweight and obese

BrooklynDodger Comments: Basically, this study provides only equivocal evidence for increased injury risk associated with increased BMI, and that mostly in women. A risk ratio of 2 is pretty strong, driven by MSD's, but two adjustments were needed to the model to get marginal statistical significance.

This population survey observed that 14% of respondants suffered an injury requiring greater than first aid treatment. Only 2% of respondents confessed being very obese. A BMI of 35 in a 6 foot tall person is a weight of 258, which is undersized for an NFL linebacker... The Dodger is no fan of overweight, but also no fan of the trend to blame victims as a softening up process for cutting health care benefits.

The survey observed that about 35% of injuries occurred at work. Considering maybe 40% of waking hours are at work, and less than 100% of the respondents were economically active [actual number not found by BD, maybe not asked], work is riskier than not working for injury. About 35% of injuries were over exertion [that is, MSD's]; these were the only category where the obese were higher than the non obese.

An association of overweight with back injury has a biomechanical plausibility. The increase might also arise from a common driver of health risk behavior [over eat] with injury risk behavior.

The investigators give us two weasel words, "suggest" and "may" in their conclusion: "The findings suggest that efforts to promote optimal body weight may reduce not only the risk of chronic diseases but also the risk of nonfatal unintentional injuries among obese individuals."

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