Study shows BMI levels impact health care costs
Number of claims higher for at-risk employees
A study of 3,066 First Chicago NBD employees has shown that people who are at risk for BMI (body mass index) "are more likely to have additional health risks, short-term disability and illness absence, and higher health care costs than those not at risk for BMI."1
BMI is calculated by taking an individual’s weight in kilograms and dividing it by their height in meters squared. The National Institutes of Health defines obesity as a BMI of 27.8 or higher for men and 27.3 or higher for women, which represents about 124% and 120% of desirable weight, respectively.
The mean health care costs for the BMI at-risk population in the study was $6,822, compared with $4,496 for the not at risk population. When sick days were converted to costs (average cost per sick day was $189), those at risk for BMI cost an average of $1,546 per person, while those not at risk for BMI cost $683 per person.
Why study BMI?
There have been any number of studies linking obesity with increased health problems and health care costs. What the researchers in this study sought to determine was if a "progressive correlation" existed between BMI, health care costs and absenteeism — that is, the higher the BMI, the higher the health care costs.
Why was it so important to focus on BMI? "Basically, because overweight’ was just a general term before, as in overweight vs. normal weight, and people just drew a line somewhere," explains Alyssa B. Schultz, MS, research associate at the University of Michigan Health Management Research Center, Ann Arbor, and co-author of the paper. "Someone above that level tended to cost more than someone of normal’ weight. We wanted to see if it was true that as you got more and more overweight it was more and more costly."
And did they? "The progressive correlation did bear up in the study," she replies. What we also found is that there’s a group of people who are underweight who cost more than what we term normal. This occurs in individuals who generally have a BMI less than 18 — but it’s not progressive."
Other significant findings
Schultz notes several other significant findings in the study. "We found that not only were overweight people at risk for weight, but for other factors as well; so obesity is doubly bad," she says. "Overweight employees tended to have additional risk factors — they smoked, had high blood pressure, and so forth. High BMI was rarely found in a vacuum."
The study also showed that cost increases were different for different disease categories. "For example, being overweight showed up more in musculoskeletal disorders than in mental disorders," Schultz explains. "And when we looked at a person’s whole cost and then the different diseases, there was a different cost curve for different weight levels."
The link to increased absenteeism costs was also "a fairly new finding," Schultz adds, although the researchers did not look for a progressive correlation in this area.
Another highly significant finding is that the greatest contributing factor to the increased medical costs for at-risk employees was the number of claims, rather than the cost. In other words, people with higher BMIs saw their doctors more often, but for less expensive claims, than those employees with lower BMIs. "This needs to be looked at more closely," says Schultz. "One possible reason for this is that this employee population is relatively young; we’re not looking at heart disease here — but back strain, knee problems, and so forth."
One of the most dramatic statements in the study was that "previous estimates of the economic impact of obesity to the employed population probably have been conservative."1
Why did the authors make such an assertion? "Researchers have never looked at absenteeism before, and health care costs alone do not tell the whole story," Schultz explains. "Now, with our productivity study, we find that along with health risk factors comes a reduced performance at work, as demonstrated by an increase in STD [short-term disability] among at-risk employees."
Schultz has this take-home’ message for wellness professionals: "What we’ve learned is that you need to attack multiple issues, not just weight issues," she advises. "As we saw, these employees are at risk in other areas as well, so take a multifaceted approach. We really feel you should address these [weight] problems when they’re not that serious, when the employees are young, to prevent them from getting more serious in the future."
Reference
1. Burton WN, Chen C-Y, Schultz AB, Edington DW. The economic costs associated with body mass index in a workplace. JOEM 1998; 40:786-792.
[For more information, contact: Alyssa Schultz, University of Michigan Health Management Research Center, 1027 E. Huron, Ann Arbor, MI 48104-1688. Telephone: (734) 764-3732. E-mail: abelaire@umich. edu.]
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