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Impact of morbid obesity on medical expenditures in adults

Abstract

CONTEXT:

Morbid obesity (body mass index (BMI) ≥40 kg/m2) is associated with substantially increased morbidity and mortality from chronic health conditions and with poorer health-related quality of life; however, less is known about the impact of morbid obesity on healthcare expenditures.

OBJECTIVE:

To examine the impact of morbid obesity on healthcare expenditures using a nationally representative sample of US adults.

DESIGN, SETTING, AND PARTICIPANTS:

We performed a cross-sectional analysis of 16 262 adults from the 2000 Medical Expenditure Panel Survey, a nationally representative survey of the noninstitutionalized civilian population of the United States. Per capita healthcare expenditures were calculated for National Institutes of Health BMI categories, based on self-reported height and weight, using a two-part, multivariable model adjusted for age, gender, race, income, education level, type of health insurance, marital status, and smoking status.

MAIN OUTCOME MEASURES:

Odds of incurring any healthcare expenditure and per capita healthcare expenditures associated with morbid obesity in 2000.

RESULTS:

When compared with normal-weight adults, the odds of incurring any healthcare expenditure in 2000 were two-fold greater among adults with morbid obesity. Per capita healthcare expenditures for morbidly obese adults were 81% (95% confidence interval (CI): 48–121%) greater than normal-weight adults, 65% (95% CI: 37–110%) greater than overweight adults, and 47% (95% CI: 11–96%) greater than adults with class I obesity. Excess costs among morbidly obese adults resulted from greater expenditures for office-based visits, outpatient hospital care, in-patient care, and prescription drugs. Aggregate US healthcare expenditures associated with excess body weight among morbidly obese US adults exceeded $11 billion in 2000.

CONCLUSIONS:

The economic burden of morbid obesity among US adults is substantial. Further research is needed to identify interventions to reduce the incidence and prevalence of morbid obesity and improve the health and economic outcomes of morbidly obese adults.

Introduction

The prevalence of morbid obesity, also termed class III or extreme obesity (body mass index (BMI) ≥40 kg/m2), is rising twice as fast as the prevalence of obesity (BMI ≥30 kg/m2) in the United States.1,2 Between 1990 and 2000, the prevalence of morbid obesity increased from 0.78 to 2.2%, representing a total of over 4.8 million morbidly obese US adults in the year 2000.3 Morbid obesity is associated with a substantially increased risk of morbidity and mortality from chronic health conditions, such as diabetes, hypertension, cardiovascular disease, and cancer,4,5,6,7,8,9 and it has been linked to multidimensional impairments in health-related quality of life and psychosocial well-being.10,11

Several articles have examined the impact of obesity, broadly defined as BMI ≥30 kg/m2, on medical expenditures in the United States.12,13,14 Another recent article also examined the impact of ‘severe’ obesity, defined as a BMI ≥35 kg/m2, on medical expenditures for adults aged 50–69 y in 1992 and found that total expenditures among severely obese adults were 60% greater than for normal-weight adults.15 Highlighting the disproportionate medical expenditures incurred by people in specific classes of obesity can help inform ongoing health policy and insurance coverage discussions regarding weight-loss interventions and programs (eg bariatric surgery). To this end, we examined the impact of morbid obesity on healthcare expenditures using a nationally representative sample of US adults.

Methods

Medical Expenditure Panel Survey population and data

We analyzed data from the 2000 Medical Expenditure Panel Survey (MEPS).16 MEPS was designed to provide nationally representative estimates of healthcare use, expenditures, sources of payment, and insurance coverage for the US civilian noninstitutionalized population. In MEPS, healthcare expenditures are defined as the sum of direct payments for care provided during the year (office- and hospital-based care, home healthcare, dental services, vision aids, and prescribed medicines), including out-of-pocket payments and payments by private insurance, Medicaid, Medicare, and other sources. Payments for over-the-counter drugs and for alternative care services are not included in MEPS total expenditure calculations.

MEPS also provides information about each person's health status and sociodemographic characteristics, including self-reported height and weight. For purposes of confidentiality, height was capped at 6 feet 5 inches and weight was capped at 350 pounds. We analyzed BMI using the 1998 National Institutes of Health (NIH) classification scheme: underweight (BMI <18.5 kg/m2), normal weight (BMI 18.5–24.9 kg/m2), overweight (BMI 25.0–29.9 kg/m2), class I obesity (BMI 30.0–34.9 kg/m2), class II obesity (BMI 35.0–39.9 kg/m2), and class III obesity (BMI ≥40.0 kg/m2).17 For our analyses, we excluded participants who refused to provide height or weight data (n=936), were under age 18 y (n=7338), or were pregnant (n=384). Our final sample included 16 262 adults aged 18 y or older, of whom 507 had class III obesity.

Statistical methods

We used a two-part model to estimate total healthcare expenditures for US adults by BMI category.18 In the first part of the model, we used logistic regression to predict the probability of incurring any healthcare expenditure in 2000. For the second part, we used the algorithm of Manning and Mullahy19 to identify the most appropriate model specifications to predict health expenditures for adults who incurred any healthcare expenditures in 2000. Expenditures were log-transformed to estimate an ordinary least squares equation and address the substantial kurtosis (>3) exhibited in the residuals. Heteroskedasticity was not evident, so expenditures were retransformed using the Duan nonparametric procedure to obtain predictions expressed in dollars.18,19 We calculated overall annual per capita expenditures by multiplying each individual's probability of incurring any expense by his or her predicted expenditure. Using these same methods, we also calculated annual per capita expenditures for office-based visits, outpatient hospital visits, in-patient hospital visits, and prescription drugs. The two-part model does not allow statistical tests of equivalence for overall predicted expenditures; therefore, 95% confidence intervals (CIs) were generated by bootstrapping with 1000 repetitions. All regression models were adjusted for gender, race/ethnicity, age, region, household income, education level, marital status, type of health insurance, and smoking status.

For each BMI category, we used the per capita expenditure predictions to construct two additional estimates of expenditures associated with excess body weight: (1) the percentage of per capita expenditures associated with excess body weight, and (2) aggregate US expenditures associated with excess body weight. The percentage of per capita expenditures associated with excess body weight in each BMI category was calculated by dividing the overall per capita expenditures associated with excess body weight (overall per capita expenditures for the BMI category minus overall per capita expenditures for the normal-weight reference group) by overall per capita expenditures for the BMI category.12,20 Aggregate national expenditures associated with excess body weight in each BMI category were calculated as the product of the percentage of aggregate US expenditures associated with each BMI category times the MEPS estimates of total US expenditures for nonpregnant adults in 2000 in each BMI category.12,20

Finally, to examine the possible impact of BMI underestimation on our results due to self-reported height and weight,21 we ran our entire two-step model and bootstrap procedure using BMI values that were corrected for self-report bias using correction factors for self-reported BMI from the Third National Health and Nutrition Examination Survey.22 Results were substantively similar, so the uncorrected results are presented. We conducted all of our analyses with STATA 8.0 SE (Stata Corporation, College Station, TX, USA), using survey commands to control for the complex design used in MEPS. The Institutional Review Board of the University of Cincinnati approved this study.

Results

The prevalence of morbid (class III) obesity among adults in the 2000 MEPS sample was 2. 8%; 35.7% were overweight, 14.6% had class I obesity, and 5.1% had class II obesity (Table 1). When compared with normal-weight adults, those with morbid obesity were more likely to be female, African-American, living in the southern United States, and living in a household with an income below 200% of the federal poverty level. Morbidly obese adults were less likely to smoke, be married, have received a college or postgraduate degree, and have private health insurance.

Table 1 2000 MEPS participant characteristics by BMI categories

After adjusting for age, gender, race/ethnicity, income, education level, type of health insurance, marital status, and smoking status, the odds of incurring any health expenditure in 2000 were two-fold greater among adults with morbid obesity compared with normal-weight adults (Table 2). Overall per capita healthcare expenditures for morbidly obese adults were $1975 greater than normal-weight adults (81% greater; 95% CI: 48–121%), $1735 greater than overweight adults (65% greater; 95% CI: 37–110%), $1415 greater than adults with class I obesity (47% greater; 95% CI: 11–96%), and $888 greater than adults with class II obesity (25% greater; 95% CI: −2.3 to 52%). Expenditure estimates for adults with class I and II obesity were also significantly higher than the normal-weight reference group.

Table 2 Adult per capita total healthcare expenditures by BMI category, 2000

Furthermore, morbidly obese adults were more likely to incur costs for office-based visits (adjusted odds ratio (AOR) 2.0; 95% CI: 1.5–2.7), outpatient hospital care (AOR 1.9; 95% CI: 1.4–2.5), in-patient care (AOR 1.7; 95% CI: 1.2–2.3), and prescription drugs (AOR 2.8; 95% CI: 2.1–3.6). These AORs translated into 50% greater per capita annual expenditures for office visits, 195% greater expenditures for outpatient hospital care, 95% greater expenditures for in-patient hospitalizations, and 95% greater expenditures for prescription drugs.

We estimated that 45% of per capita healthcare expenditures among adults with morbid obesity were associated with excess body weight (Table 2). By comparison, 9, 19, and 31% of per capita healthcare expenditures were associated with excess body weight among overweight adults and adults with class I and II obesity, respectively. In 2000, 10% of all US healthcare expenditures were associated with excess body weight, and one-fifth of those expenditures occurred among morbidly obese adults. Thus, the aggregate healthcare expenditures associated with excess body weight in the United States reached $56 billion in 2000, and, although they represented less than 3% of the US adult population, morbidly obese US adults were responsible for over $11 billion of those expenditures (Figure 1). By comparison, the healthcare expenditures associated with excess body weight among overweight US adults, who make up over 35% of the population, amounted to $17 billion.

Figure 1
figure1

Aggregate US medical expenditures associated with abnormal body weight by BMI categories, 2000 (aggregate US expenditures associated with abnormal body weight in each BMI category were calculated by multiplying the percentage of aggregate US expenditures associated with BMI in each category by the MEPS estimates of total US expenditures for nonpregnant adults in 2000. The prevalence of each BMI category is presented on the X-axis).

Discussion

Morbid obesity is an increasingly important health problem in the United States, and our study highlights the economic impact of this condition among adults. Consistent with previous studies, we found that obesity was associated with greater healthcare expenditures in a dose-dependent fashion.12,20,23 Earlier national estimates indicated that obese adults (defined as those with a BMI ≥30 kg/m2) incurred costs that were 36–37% higher than for normal-weight adults.12,13 We found that excess costs were substantially greater for morbidly obese adults (81% greater than the normal-weight group), which is consistent with another study of adults aged 50–69 y.15 We also identified significant expenditure differences across classes of obesity—adults with class III obesity incurred $1400 more in annual per capita healthcare expenditures than the class I obesity group. This study also sheds new light on the types of healthcare services that are driving these excess expenditures. We found that morbidly obese adults had outpatient hospital expenditures that were nearly three-fold greater, and expenditures for office visits, in-patient care, and prescription drugs were two-fold greater than for normal-weight adults.

Our estimates have important implications for health insurers and policy makers because they suggest that the disproportionate cost increases experienced by morbidly obese adults might be averted by implementing programs to prevent overweight and obese individuals from becoming morbidly obese. Our findings also have important implications for the problem of rising healthcare costs in the United States. We found that 10.2% of all US healthcare expenditures ($56.0 billion in total) in 2000 were associated with excess body weight, up from a previous estimate of 9.1% ($51.5 billion) in 1998.14 If the number of overweight and obese Americans continues to increase over the next decade, and if new medical and surgical technologies are developed to treat obesity and its complications, the proportion of US expenditures associated with overweight and obesity will likely continue to rise. On the other hand, broad-based and aggressive population-level interventions to reduce the incidence and prevalence of obesity in the United States might help to slow the growth in national health expenditures.

Our study has several limitations. We found that the self-reported prevalence of morbid obesity was 0.6% greater (2.8 vs 2.2%) than what was previously reported in an analysis of data from the Behavioral Risk Factor Surveillance System, which also used self-reported height and weight;1 however, those authors limited their analyses to non-Hispanic whites, non-Hispanic blacks, and Hispanics (other racial/ethnic groups—comprising 4% of the adult population—were excluded).1 Second, the methods we used to calculate aggregate healthcare expenditures associated with excess body weight are widely accepted,12,14,15,20,23 but those methods are more appropriately applied to incident—not prevalent—conditions and assume no confounding of the exposure–outcome relationship.24 In this analysis, the obesity–expenditure relationship may be confounded by unmeasured health conditions (eg physical disability). Further research is needed to establish an unbiased method of calculating estimates of obesity-attributable expenditures, accounting for the complex causal relationships between body weight and chronic medical conditions.

In conclusion, the economic burden of morbid obesity among US adults is substantial. If the prevalence of morbid obesity continues to increase over the next decade, obesity-associated healthcare expenditures will likely rise at an alarming rate. Furthermore, given the high cost of morbid obesity ascertained in this study, public and private payers may find value in weight loss interventions, such as bariatric surgery, that have been shown to be cost effective in treating morbidly obese patients.25,26 This report should serve to mobilize interest and resources toward dealing with the problem of morbid obesity.27 Improving our knowledge of how and why morbidly obese adults use healthcare services may lead to better care for these individuals. More research is needed to identify the factors driving medical expenditures among morbidly obese adults and to establish system-level strategies that improve the management of patients with morbid obesity and reduce its associated costs.28

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Correspondence to D E Arterburn.

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Arterburn, D., Maciejewski, M. & Tsevat, J. Impact of morbid obesity on medical expenditures in adults. Int J Obes 29, 334–339 (2005). https://doi.org/10.1038/sj.ijo.0802896

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Keywords

  • health services
  • economic
  • cost
  • overweight

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