In-patient obesity diagnosis, use of surgical treatment and associated costs by payer type in the United States: Analysis of the National Inpatient Sample, 2011 through 2014

Summary

This study aims to examine the trend in the diagnosis of obesity and the use of surgical treatment in in-patient settings as well as per person and national costs associated with the surgical treatment of obesity. We conducted cross-sectional and trend analyses of in-patient obesity diagnosis and surgical treatment for obesity using data from the National Inpatient Sample (2011–2014) of adult patients in the United States aged 18 years and older. We studied the rate of in-patient obesity diagnosis among hospitalized patients, the rate of bariatric surgery among patients diagnosed with obesity in the hospital, and the costs associated with surgical treatment. Trend analyses showed a statistically significant increase in the proportion of (a) hospitalized patients diagnosed with obesity, and (b) bariatric surgery among those diagnosed with obesity and among different socio-demographic and insurance groups. Despite the increase in the national in-patient cost, the average in-patient cost per hospitalization associated with bariatric surgery decreased from 2012 to 2014. With the increase in the rate of diagnosed obesity and bariatric surgery among hospitalized patients and the decrease in the average in-patient cost, future research should address the short- and long-term cost-effectiveness of bariatric surgery on chronic diseases.

1 |. INTRODUCTION

In 2016, the global prevalence of obesity in adults was 13%, with the highest obesity rate in the United States.^1,2 The prevalence of adult obesity in the United States increased from 30.5% in 2000 to 39.6% by 2016.³ Obesity has been identified as one of the biggest drivers of preventable chronic diseases and rising healthcare costs in the United States.⁴ Additionally, it is a risk factor for many conditions such as high blood pressure, cardiovascular diseases, type 2 diabetes, certain types of cancer, gallbladder disease and arthritis.^5–7 Estimates of obesity-related health care costs range from $147 billion to nearly $210 billion per year.^8,9 Extant trend studies related to obesity treatments show growth in the number of surgeries^10,11 and also report inequity in bariatric surgery with publicly insured patients undergoing surgery at lower rates.¹² The US healthcare system includes a variety of private and public insurance. Private insurance is employer-sponsored and insures the largest share of the US population. The two largest public payers in the United States are the Medicare and Medicaid programs, which primarily support older and lower-income individuals, respectively.¹³ However, no study has yet looked at the cost of bariatric surgeries associated with payer type.

Practice guidelines for the treatment of obesity suggest clinicians offer or refer adults with a body mass index (BMI) of 30 or higher to intensive, multicomponent behavioural interventions.¹⁴ Behavioural interventions include a focus on diet and exercise, behaviour modifications, and pharmacotherapy regimens.^15,16 These options are typically used as first-line treatments for obesity. When such interventions are ineffective, the next treatment approach is surgery. Surgery includes bariatric and gastric bypass surgeries, among others.¹⁷ The updated recommendations for bariatric or weight loss surgery are if the patient has a BMI more than 40, or if the BMI is more than 35 and the patient has an obesity associated illness, per the International Federation for the Surgery of Obesity and Metabolic Disorders (IFSO).¹⁸ These surgeries are immediate weight loss interventions and are feasible when first-line treatment has failed. Such surgeries are also the only long-lasting options for individuals with severe and complex obesity. Furthermore, it has also been shown that bariatric surgery is not only effective treatment for obesity but also reduces the incidence or severity of chronic diseases. While earlier studies have shown that in some cases, bariatric surgery can cause regaining of weight, and severe complications, more recent studies demonstrate that laparoscopic technology has decreased the mortality rate associated with the surgery.¹⁹

There are disparities in obesity prevalence and treatment based on socio-demographic characteristics. For example, obesity prevalence is higher among the low-income population,²⁰ who are likely to receive health insurance coverage through public options, most commonly Medicaid. Similarly, previous studies have shown a disparity in obesity prevalence by age, race, and sex overall and within both rural and urban areas.^21–23 The obesity rate is the highest among Hispanics, followed by Blacks, and then Whites.²⁴ In the present study, we used data from the National Inpatient Sample (NIS) to assess the most recent trends in the rate of in-patient obesity diagnosis and surgical treatment of obesity in the United States. We analysed these trends by age, sex, race and payer type. We then estimated the costs associated with surgery by payer type. Analysis of cost by payer type allows us to compare the economic burden of in-patient obesity treatment in private and public insurance.

2 |. METHODS

2.1 |. Data

This study utilized National Inpatient Sample (NIS) data from 2011 to 2014, obtained from the Healthcare Cost and Utilization Project (HCUP) of the Agency for Healthcare Research and Quality. NIS is the largest publicly available hospital discharge database that provides information on in-patients entering community hospitals in the United States. According to the HCUP report, it contains more than 8 million discharges from about 20% of community hospitals.²⁵ The study is limited to adult patients, 18 years and older, for the period from January 1, 2011, to December 30, 2014. We defined diagnosed obesity using the International Classification of Diseases, 9th Revision Clinical Modification (ICD-9-CM) Code.

2.2 |. Measures

We defined a hospitalization with an in-patient obesity diagnosis code in the NIS data as any record with one of the following ICD-9-CM codes: obesity (278.00), morbid obesity (278.01), obesity hypoventilation syndrome (278.03), or a diagnosis-related group code of 288 (DRG is a patient classification system that standardizes prospective payment to hospitals and to classify hospital cases into one of approximately 500 groups using specific codes). The NIS data did not differentiate primary or secondary diagnostic codes. We identified hospitalization cases for bariatric surgery among patients with an obesity diagnosis using a large number of ICD-9-CM codes^a (see Appendix Table A1 for the complete list). Some studies report an under-diagnosis of obesity in community health centres; however, our research is based on the hospitalized patient, and it has been found that hospitalization offers healthcare providers a chance to identify obesity and initiate weight management interventions.^26,27 Finally, we stratified the sample by age, sex, race and payer type.

2.3 |. Statistical analysis

The analysis consists of three main parts. First, we performed descriptive analyses to study the trends in the prevalence of diagnosed obesity among all hospitalizations and the proportion of bariatric surgeries among hospitalizations of adult patients with an obesity diagnosis (number of bariatric surgery cases divided by the total number of cases with an obesity diagnosis). Second, we stratified the trends in hospitalization with an obesity diagnosis by age group (18–34 years, 35–54 years, 55–64 years vs ≥65 years), sex (Men vs Women), race (non-Hispanic White, non-Hispanic Black, Hispanic, Asian, Native American vs Other races) and payer type (Medicaid, Medicare, Private Insurance, Self/Others). For all analyses, to create national estimates for the prevalence of obesity diagnosis, we applied trend weight (TRENDWT) through Stata’s ‘svy’ command for the year 2011, while we implemented discharge weight (DISCWT) for years from 2012 to 2014. Due to the redesign of NIS data beginning with the year 2012, we applied TRENDWT only in the year 2011. We tested statistical significance for trends using a chi-square test. Finally, we examined the cost per in-patient hospitalization for bariatric surgery by payer type and estimated the total costs for these surgeries in each year of study. To deal with the skewed distribution of the cost data, we utilized generalized linear models with the log link and gamma distribution to estimate the in-patient costs (inflation adjusted to 2014 US dollars^b) associated with bariatric surgeries, controlling for patient and hospital factors. Cost-to-charge ratios by year were used to convert the hospital charges into estimated actual payments.²⁸ We conducted all statistical analyses using Stata S.E. 15.

3 |. RESULTS

Based on the NIS, there were 3.6 million in-patient obesity diagnoses among all hospitalizations in 2011. The number of in-patient obesity diagnoses increased to 4 million in 2014. Table 1 shows the total number per year and the rate of in-patient obesity diagnosis per 100 000 hospitalizations by age, sex, race and payer type. The rate of in-patient obesity diagnosis was the highest among persons aged 55 to 64 years, followed by middle-aged individuals (35–54 years) across all the study years. The rate of an in-patient obesity diagnosis among hospitalizations is higher among women than in men and higher among non-Hispanic Blacks, followed by non-Hispanic Whites and Hispanics, as well as higher among those with private payer followed by Medicaid and Medicare respectively across all years. When Medicaid and Medicare patients are combined, the rate of in-patient obesity diagnosis is higher among patients with public insurance than those with private insurance. The rate of an in-patient obesity diagnosis increases from 2011 to 2014, and this trend is significant across all age groups, sex, race and payer type.

TABLE 1.

Rate (%) of in-patient obesity diagnosis among adult in-patients in the National Inpatient Sample between 2011 and 2014^a

	Year
	2011	2012	2013	2014	P trend b
N (obesity diagnosis)	3 654 251	3 658 640	3 829 409	4 085 036
Overall rate	11.1	11.9	12.8	13.7
Age
18–34 years	7.27	7.58	8.29	8.93	<.001
35–54 years	15.07	16.08	17.14	18.35	<.001
55–64 years	16.65	17.39	18.35	19.28	<.001
>65 years	8.55	9.54	10.38	11.33	<.001
Gender					<.001
Male	9.96	10.71	11.51	12.39	<.001
Female	11.90	12.72	13.66	14.66	<.001
Race					<.001
White	10.80	11.76	12.64	13.60	<.001
Black	13.69	14.74	15.56	16.53	<.001
Hispanic	11.29	11.34	12.28	13.24	<.001
Other racesc	9.78	9.77	10.55	11.36	<.001
Payer					<.001
Medicaid	11.10	11.79	12.54	13.48	<.001
Medicare	10.38	11.45	12.31	13.32	<.001
Private	12.33	13.02	14.01	14.95	<.001
Self/Others	10.75	11.01	11.84	12.24	<.001

^aSampling weight adjusted in all statistics.

^bTest for trend analysis was examined using ‘ptrend’ command in Stata (it provides a chi-square statistic for trend across the groups).

^cOther races include Asian Americans or Pacific Islanders and Native Americans.

This study also looked at the rate of surgical treatment-bariatric surgery among in-patients diagnosed with obesity within the NIS. There were close to 560 000 total cases of bariatric surgery among hospitalized patients from 2011 to 2014. Table 2 shows the proportion of patients among in-patients diagnosed with obesity getting bariatric surgery by age, sex, race and payer type. The proportion of hospitalizations with an in-patient obesity diagnosis was highest among 35–54-year-old patients, followed by 18–34-year-old patients. The proportion was also highest for patients covered by private insurance followed by self-pay. Bariatric surgery also appears to be more common among women than in men with an in-patient diagnosis of obesity. The trend in the proportion of in-patients diagnosed with obesity getting bariatric surgery increased across all age and race groups and insurance types.

TABLE 2.

Proportion of bariatric surgeries among hospitalized adults with an in-patient obesity diagnosis in the National Inpatient Sample between 2011 and 2014^a

	2011	2012	2013	2014	P trend b
N (bariatric surgeries)	111 468	133 915	152 310	161 925
Overall proportion	3.05	3.66	3.98	3.96
Age
18–34 years	5.28	6.01	6.43	6.12	<.001
35–54 years	5.21	6.49	7.23	7.34	.003
55–64 years	2.35	2.86	3.01	3.01	<.001
>65 years	0.63	0.71	0.84	0.89	<.001
Gender
Male	1.85	2.16	2.29	2.34	.287
Female	3.73	4.53	4.96	4.92	.117
Race
White	3.17	3.61	3.94	3.90	<.001
Black	2.38	3.05	3.56	3.59	<.001
Hispanic	3.44	4.68	4.85	4.85	<.001
Other racesc	3.08	4.14	4.11	4.14	<.001
Payer					<.001
Medicaid	2.28	2.39	2.56	2.66	<.001
Medicare	1.14	1.25	1.46	1.51	<.001
Private	5.99	7.92	8.70	8.39	<.001
Self/Others	3.17	3.02	3.11	3.78	<.001

^aSampling weight adjusted in all statistics.

^bOther races include Asian Americans or Pacific Islanders and Native Americans.

^cTest for trend analysis was examined using ‘ptrend’ command in Stata.

Table 3 shows the average length of stay, average in-patient costs per hospitalization, and the national total in-patient costs associated with bariatric surgeries in the NIS. The average length of stay decreased from 2.41 days in 2011 to 2.21 days in 2014, which may partly explain the decreasing trend in the average total in-patient cost for bariatric surgeries in in-patient settings. Finally, while the average total in-patient cost per hospitalization has decreased during this period, the national total in-patient cost is increasing, as there is an increasing number of surgeries in hospitals. The average per-person in-patient cost is highest among Medicare patients, while the total national in-patient cost is highest among the private payers.

TABLE 3.

Average length of stay and in-patient costs per hospitalization associated with bariatric surgeries in the National Inpatient Sample between 2011 and 2014

	2011	2012	2013	2014
N (Bariatric surgeries)	111 468	133 915	152 310	161 925
Average length of stay (days)	2.41	2.36	2.25	2.21
Average in-patient cost ($)a	13 623.42	14 147.85	13 528.75	13 067.85
Average in-patient cost for Medicare	15 314.59	16 280.48	14 934.26	14 864.66
Average in-patient cost for Medicaid	14 660.17	13 873.44	13 337.37	12 851.50
Average in-patient cost for Private	13 521.26	13 724.09	13 263.44	12 690.47
Average in-patient cost for Self/Others	12 855.60	13 916.69	12 975.42	12 420.81
National in-patient cost ($million)	314	374	411	422
National in-patient cost for Medicare	57	66	75	83
National in-patient cost for Medicaid	38	38	40	49
National in-patient cost for Private	200	245	270	266
National in-patient cost for Self/Others	25	26	26	24

^aPredicted average in-patient cost was estimated using generalized linear models adjusting for age, age square, gender, race/ethnicity, payers, number of co-morbidities and hospital-level characteristics.

4 |. DISCUSSION

We found an increasing trend in the rate of in-patient obesity diagnosis and the proportion of diagnosed cases getting bariatric surgery among adult patients age 18 or older in the United States over the 4-year study period from 2011 through 2014. Extant studies on trends in bariatric surgery include three types of bariatric surgery (the Rouxen-Y gastric bypass, adjustable gastric banding and sleeve gastrectomy). Our research consists of a more comprehensive list of the types of bariatric surgery and is unique in the assessment of the trends and costs by payer types. The rate of in-patient obesity diagnosis increased during this period across all age and race groups and payer types. The rate of an in-patient obesity diagnosis was highest among hospitalizations of Black patients across all study years. However, the proportion of bariatric surgeries among hospitalizations with an in-patient obesity diagnosis was the highest among Hispanic across all the years. These results suggest racial differences in the rate to seek surgery as a treatment for obesity.

Several factors might contribute to the increasing trend in in-patient obesity diagnosis. The overall prevalence of obesity among adults increased from 35% in 2005–2006 to 38% in 2013–2014.²⁹ In response, the public health and medical sectors have aimed their policy agendas and goals at curbing the obesity epidemic. For example, the American Medical Association’s (AMA) recognized obesity as a disease in June of 2013.³⁰ Besides, many aspects of the Patient Protection and Affordable Care Act (ACA), a US comprehensive healthcare reform law enacted in March 2010 with a major goal to increase access to health insurance in the United States, were implemented during this time. Before the ACA, most states allowed insurance companies in the individual market to deny health insurance coverage or set rates based on health status.³¹ Therefore, implementation of the ACA may have contributed to the increase in surgeries. Further, Medicaid expansion might have made obesity treatment more accessible under ACA. Medicaid and state employee programs experienced an increase in physician recommendations and patient demand for obesity treatment services (nutritional counselling, bariatric surgery and pharmacotherapy) from 2009 to 2017 in many states. Furthermore, the US Preventive Services Task Force (USPSTF) issued its recommendation on screening for obesity in adults in 2012, which has been recently updated.³² In the update, the USPSTF recommends that clinicians offer or refer adults with a BMI of 30 or higher to intensive, multicomponent behavioural interventions.¹⁵

The observed in-patient costs ($13 067 per hospital stay in 2014) are comparable to previous estimates reported in the literature.^33–35 The total national cost estimated in this study ($422 million in 2014) is also comparable to previous estimates. The trend results in this study show a clear pattern. Patients seem more likely to opt for surgeries with private insurance, followed by self-pay, Medicaid and Medicare. Surgical treatment options for obesity are likely to incur higher initial costs, compared to non-surgical treatment options. Still, they may lower long-term costs by providing a more effective, long-lasting treatment. Previous work has suggested that the long-term benefits of bariatric surgeries outweigh the costs.³⁶ However, bariatric surgery is not the ultimate cure for all patients affected by obesity as some patients regain weight post-surgery. The medical sector has shifted its recommendations by lowering the BMI qualification to 30 kg/m² or greater with co-morbidities if substantial weight loss would be beneficial for the individual.³⁷ At present, patients with BMI > 35 kg/m² and co-morbidities or patients with BMI > 40 kg/m² qualify for bariatric surgery. Future studies should identify the best time for surgery to maximize long-term health benefits and reduce future medical costs. The importance of studying the trend and cost-effectiveness of bariatric surgery holds true for the 2/3 of the US population who are overweight or affected by obesity. However, continuous efforts to strengthen public health policy and healthcare services to prevent the remaining 1/3 population from gaining weight in the first place should not be replaced by treatment-oriented efforts.³⁸

Also, it appears that while bariatric surgery is a treatment for obesity, a risk factor for many chronic diseases. Therefore, bariatric surgery potentially could be a procedure to prevent chronic diseases. For example, bariatric surgery can be an effective treatment for Type 2 diabetes. More research is needed in this area, and future research should address the short- and long-term cost-effectiveness of bariatric surgery. First, to recommend the most effective age for surgery for the highest return across the lifetime and second to find if surgery is more cost-effective compared with existing approaches such as behavioural counselling and new approaches such as laparoscopic technologies, across different age groups and payers. Moreover, choosing the best primary procedure may increase the likelihood of long-term success and consequently reduce reliance on surgical revisions.³⁹

This study updates the literature on trends in in-patient obesity diagnoses and surgical procedures for obesity treatment and the associated costs for bariatric surgeries. However, the study is limited to in-patient visits and costs only. In recent years, the Food and Drug Administration has approved several different outpatient treatment therapies for obesity. Hence, the bariatric surgery estimate in this study is an underestimation as many of those surgeries (typically gastric bands and sleeve gastrectomy) are now done in an outpatient setting.^40,41 Also, non-surgical treatments for obesity, including gastric balloons and other procedures performed by gastroenterologists and others, are increasingly common, which we could not identify in our in-patient database. In addition, it is likely that we underestimate the rate of bariatric surgeries due to the preauthorization requirement that bariatric surgery needs to have a diagnosis for severe and complex obesity or obesity with a co-morbid condition. Further, the number of bariatric surgeries each year is small, which limits our analysis to estimate the in-patient cost associated with each type of surgery. The study period is limited to 2011 to 2014; the in-patient claims data in the fourth quarter of 2015, and onwards used the ICD-10 coding system that may cause discrepancies in identifying the obesity diagnosis. Finally, states differ in their coverage for obesity prevention and treatment services^31,42; however, the NIS data does not include state identifiers for the study years.

5 |. CONCLUSIONS

From 2011 to 2014 in the United States, there was an increase in obesity diagnoses in hospitalized patients and bariatric surgeries among those diagnosed with obesity. An in-patient obesity diagnosis was most likely among women, non-Hispanic Blacks, and those with public insurance. Bariatric surgeries were most common in 33–54-year-old patients with private insurance. These trends were consistent among different socio-demographic and insurance groups. Total in-patient expenditures on bariatric surgery increased over this period, while the average in-patient cost per hospitalization decreased. Future research should address whether bariatric surgery is a cost-effective option for the treatment of chronic diseases.

What is already known about this subject?

• There has been an increase in the use of bariatric surgery to treat individuals affected by obesity.

• Socio-demographic disparities exist in obesity prevalence and treatment.

What this study adds?

• Both obesity diagnosis and surgery among those diagnosed is increasing.

• The increase is across different socio-demographic and insurance groups.

• The average in-patient cost associated with bariatric surgery has decreased.

GLOSSARY

Medicare

Health insurance provided by the US Federal Government for people age 65 years and older.

Medicaid

Health insurance provided by the US Federal and State Government for people with low income.

Patient Protection and Affordable Care Act (ACA)

A comprehensive healthcare reform law enacted in the United States in March 2010.

National Inpatient Sample (NIS)

The largest publicly available hospital discharge database with information on in-patient discharges in community hospitals in the United States.

APPENDIX

TABLE A1.

ICD-9-CM diagnosis codes used to identify bariatric surgeries

Description	ICD-9-CM code
Partial gastrectomy with anastomosis to oesophagus	43.5
Partial gastrectomy with anastomosis to duodenum	43.6
Partial gastrectomy with anastomosis to jejunum	43.7
Other partial gastrectomy	43.8
Partial gastrectomy with jejunal transposition	43.81
Laparoscopic vertical (sleeve) gastrectomy	43.82
Laparoscopic gastric restrictive procedure with gastric bypass and Roux en Y gastroenterostomy	43.844
Open and other partial gastrectomy	43.89
Total gastrectomy	43.9
Total gastrectomy with intestinal interposition	43.91
Other total gastrectomy	43.99
Gastroenterostomy without gastrectomy	44.3
High gastric bypass	44.31
Laparoscopic gastroenterostomy	44.38
Other gastroenterostomy without gastrectomy	44.39
Revision of gastric anastomosis	44.5
Esophagogastroplasty	44.65
Other procedures for creation of oesophagogastric sphincteric competence	44.66
Laparoscopic procedures for creation of oesophagogastric sphincteric competence	44.67
Laparoscopic gastroplasty	44.68
Laparoscopic gastric restrictive procedure	44.95
Laparoscopic revision of gastric restrictive procedure	44.96
Laparoscopic removal of gastric restrictive device(s)	44.97
Laparoscopic adjustment of size of adjustable gastric restrictive device	44.98
Other operations on stomach	44.99
Revision of gastric anastomosis	(DRG) 288

Note: Coding for bariatric surgeries is from multiple sources.

https://www.healthgrades.com/quality/2014-healthgrades-bariatric-surgery-report-volume-plays-role-in-quality-outcome

https://www.soard.org/cms/10.1016/j.soard.2018.04.002/attachment/b2abeb6f-2529-4004-a26f-79eb2d15fbd8/mmc1.docx

https://www.ncbi.nlm.nih.gov/books/NBK63485/pdf/Bookshelf_NBK63485.pdf