I have previously posted on the issue of motor vehicle injuries and obesity.
Now a study published by Dietrich Jehle and colleagues from the Buffalo School of Medicine, NY, in the American Journal of Emergency Medicine, again reports greater fatality risk in individuals with moderate or severe obesity (20 and 60% higher, respectively).
The researchers looked at fatalaties in 155,584 drivers included in the 2000-2005 Fatality Analysis Reporting System stratified by body mass index.
Interestingly, fatality rates in people who were overweight (BMI 25 to <30) or slightly obese (BMI 30 to <35) was actually lower than in those with “normal weight” (BMI 18.5 to <25) or “underweight” (BMI
Thus, as the authors discuss, while a bit of extra fat may prove effective as “cushioning” in preventing more severe injuries, this effect is lost at higher weights.
This may have to do with more that just the excess body fat.
As the authors note:
“An obese driver is forced to sit closer in proximity to the steering column and has less time to reduce his or her increased momentum. Most manufacturers design and test vehicle interiors in accordance with the federal motor vehicle safety standards that use a 50th percentile (BMI, 24.3 kg/m2) male dummy. These designs may not be ideal for the more than one third of the US adult population that is obese.”
I’d certainly like to hear from my readers on what they think about excess weight an motor vehicle safety.
I look forward to your comments.
Jehle D, Gemme S, & Jehle C (2012). Influence of obesity on mortality of drivers in severe motor vehicle crashes. The American journal of emergency medicine, 30 (1), 191-5 PMID: 21129887
Today, I am attending the 8th World Congress on Trauma, Shock, Inflammation and Sepsis in Munich, Germany.
Interestingly, this conference features a whole series of seminars on the interdisciplinary management of obesity (under the rather unfortunate title ‘Fat Man – We Will Help You’ [sic]).
I have been invited to chair and speak at the session on medical therapy, but there are also sessions on adipose tissue biology, perioperative management, bariatric surgical procedures, and the emergency management of bariatric patients.
As I often say in my presentations to colleagues: it does not matter what discipline in medicine you practice – you will be seeing an increasing number of heavier patients with their own issues and complications.
The fact that a world conference on trauma should devote this much time to sessions on obesity assessment and management is clearly to be commended in the light of the global obesity epidemic.
The more all health professionals learn and understand the complexities and problems posed by heavier patients, the better we can serve this particularly vulnerable patient population.
Regular readers of these pages may recall a previous article on the development of bariatric crash test dummies.
A new paper, just published in the Journal of Trauma now provides new evidence on just how important this work can be.
In this study Fernanda Tagliaferri and colleagues from the Ospedale Cesare Magati, Scandiano, Italy, analysed data from all front seat occupants with at least one injury, older than 16 years old involved in a frontal collision from 1993 to 2005 from the National Automotive Sampling System (NASS) database.
In this analysis of almost 6000 patients, obese occupants had an 85% higher risk of a fatal outcome and an almost 40% higher risk of a severe injury. Of particular concern is the fact that obese occupants had an almost 2 fold higher incidence of sustaining the most severe type of head injury.
These findings are of particular significance as severely obese patients are often unable to comfortably use the seat belts in most cars.
Obviously, a topic that poses some challenges for car makers and trauma centres alike (not to mention the obese occupants themselves).
On Saturday (June 7), I presented at a session on How Obesity Affects Orthopaedic Care at the 2nd joint meeting of the American and Canadian Orthopaedic Associatons in Quebec City.
Despite being on the last day of this meeting, the session was surprisingly well attended, probably a reflection of the increasing awareness of issues around orthopaedic care for patients with severe obesity.
While I presented my usual take on how obesity is now a widespread chronic disease, I did take away some interesting aspects related to orthopaedic care of patients with obesity that I was unaware of.
For example, George Russell (Jackson, Mississippi) in his talk mentioned the issue that in severely obese patients immobilization of fractures with a plaster cast poses a significant problem due to the “cushioning” effect of the surrounding adipose tissue. This results in an increased risk of “non-union”, often requiring additional internal or external fixation to ensure healing.
Russell also presented an interesting view of how differences in body fat distribution pose specific problems in orthopedic surgery on hips and knees. Thus, in patients with the “large belly – thin limb” phenotype, the operation on the limbs is relatively easy, but, given the association between large bellies and cardiometabolic risk, these patients are at greater risk for poor wound healing and cardiovascular problems. In contrast, patients with “large limbs – thin bellies” present problems related to the size of the limbs resulting in a greater risk for bleeding and wound infections. Obviously, patients with “large bellies – large limbs” are at increased risk for both types of complications.
In a talk on orthopaedic problems in childhood obesity, Benjamin Alman (Sick Kids, Toronto) mentioned the issue of “relatively” (i.e. in relationship to their body mass) lower bone density in children with overweight and obesity, an issue that may increase the likelihood of traumatic fractures in these kids – again, something I had not previously thought much about.
Bassam Masri (UBC, Vancouver) confirmed that despite slightly greater risk and less functionality following joint replacement in patients with severe obesity, their satisfaction is no smaller than that or non-obese patients – clear indication that obese patients should not be denied surgery simply because of their size. But don’t expect to see spontaneous weight loss after surgery – in fact weight sometimes even goes up in overweight patients following surgery (I have blogged on this before).
I was particularly happy to note that all three surgeons called upon their colleagues to show compassion and deliver care with the same professional attitudes with which they approach their non-obese patients.
Overall, a most interesting session. I am delighted to see the orthopaedic surgeons taking this great interest in this (unfortunately) increasingly important issue.
Given the increase in average body size (and weight), it is not surprising that the automotive safety community is questioning the impact of obesity on the performance and assessment of occupant protection systems.
This issue was recently addressed by David Viano and colleagues, who work at ProBiomechanics LLC, a Michigan firm specializing in occupant kinematics and injury causation, published last month in Traffic Injury Prevention.
The authors investigated the relationship between fatality and serious injury risks for front-seat occupants by body mass index (BMI) using a matched-pair analysis. They also developed a simple model for the change in injury risk with obesity which includes the normal mass (m) and stiffness (k) of the body resisting compression during a blunt impact. For a given impact severity, the risk of injury was assumed proportional to compression. Energy balance was used to determine injury risks with increasing mass.
Data for 1993-1004 was analyzed from the National Automotive Sampling System Crashworthiness Data Set (NASS-CDS), an ongoing study of more than 5,000 accidents each year, in which trained investigators look at wrecked vehicles, read through police reports, and talk to accident victims. Occupant injury was divided into normal and obese categories. A matched-pair analysis was carried out. Driver and front-right passenger fatalities or serious injuries (MAIS 3+) were analyzed in the same crash to determine the effect of obesity.
Based on the model, an obese occupant (BMI = 30-35 kg/m2) has 54-61% higher risk of injury than a normal BMI occupant (22 kg/m2). Matched pairs showed that obese drivers have a 97% higher risk of fatality and 17% higher risk of serious injury than normal BMI drivers. Obese passengers have a 32% higher fatality risk and a 40% higher risk than normal passengers. Obese female drivers have a 119% higher risk than normal BMI female drivers and young obese drivers have a 20% higher serious injury risk than young normal drivers.
These data add to several prior publications highlighting the increased risk for overweight and obese drivers and passengers in automobiles.
Viano and colleagues also estimated how much extra ballast the family of Hybrid III crash test dummies would need to represent an obese or morbidly obese occupant. According to these assessments, the smallest crash test dummies need proportionately more ballast to represent an obese or morbidly obese occupant in the evaluation of safety systems. The 5% female Hybrid III (BMI = 20.4) and needs 22 kg of ballast to represent an obese and 44.8 kg to represent a morbidly obese female, while the 95% male needs only 1.7 and 36.5 kg, respectively.
The authors conclude that
“Obesity influences the risk of serious and fatal injury in motor vehicle crashes. The effect is greatest on obese female drivers and young drivers. Since some of the risk difference is related to lower seatbelt wearing rates, the comfort and use of seatbelt extenders should be examined to improve wearing rates by obese occupants. Also, crash testing with ballasted dummies to represent obese and morbidly obese occupants may lead to refined safety systems for this growing segment of the population.“
As also noted recently by Ben Zarzaur and Stephen Marshall, Surgeons at the University of Tennessee Health Science Center, Memphis, in The Journal of Trauma, the combination of obesity and not using a seat belt is particularly deadly.
Most importantly, David Schlundt and colleagues from Vanderbilt University just reported in OBESITY based on data from the 2002 Behavioral Risk Factor Surveillance System Survey, that seatbelt use declines as BMI increases, with approximately 55 percent of extremely obese individuals say that they do not use a seatbelt.
Consequence of these finding for counseling our obese patients: buy cars where seatbelts fit your size or buy seatbelt extenders AND USE THEM!
Sounds like a class-action waiting to happen!