ORIGINAL ARTICLE
Long-term Clinical Outcomes and Health Care Utilization After Bariatric Surgery A Population-based Study David J. R. Morgan, MBBS, FACEM, FCICM,∗ Kwok M. Ho, PhD, MPH, FANZCA, FCICM,† Jon Armstrong, MBBS, BA, FRACS,∗ and Edward Litton, MSc, MBBS, FCICM∗
Objective: To determine the long-term outcomes, health care utilization, and risk factors for complications after bariatric surgery. Background: With the burgeoning problem of obesity and the consequential rise in bariatric surgery, uncertainty remains as to whether this has been matched by a reduction in long-term health care utilization. Methods: A population-based linked-data cohort study, utilizing a comprehensive set of data, including detailed comorbidity and complications, of each individual who had undergone bariatric surgery between 2007 and 2011 in Western Australia. Records were obtained via data linkage through the Western Australian Department of Health Data Linkage Unit. Every patient was followed for a minimum of 12-months after surgery or until death. Results: A total of 12062 patients underwent bariatric surgery during the study period with a mean follow-up period of 41 months. Hospitalization rates after bariatric surgery were substantially reduced for all-cause (361 vs 501 per 1000 patient-years, P = 0.002) and diabetes mellitus–related (7 vs 31 per 1000 patient-years, P < 0.001) diagnoses when compared with hospitalization rates before bariatric surgery. Complications occurred in 2171 (18.0%) patients during the follow-up period. Patient age, sex, open surgical procedures, and Charlson Comorbidity Index were associated with an increased risk of complications, with age the most important and accounting for 77% of the variability in the risk of complications. Long-term all-cause mortality rate after surgery was extremely low (0.54 deaths per 1000 patient-years). Conclusions: When measured against long-term safety outcomes, bariatric surgery has low mortality and morbidity associated with a significant reduction in subsequent hospitalizations. Keywords: age, bariatric surgery, complications, long-term outcomes, mortality, population-based risk factors (Ann Surg 2015;262:86–92)
I
t is now regarded that bariatric surgery confers the most effective and durable treatment for obesity with an excellent short-term safety profile.1–3 With the establishment of bariatric surgery in the United States and its increasing acceptance elsewhere around the world,4–7 it is pivotal to confirm that the excellent short-term results after such surgery extend into the longer term by demonstrating
From the ∗ Department of Intensive Care Medicine, St John of God Hospital Subiaco, Western Australia, Australia; and †School of Population Health, University of Western Australia, Perth, Australia. Disclosure: St John of God Hospital Subiaco Research Grant: Sum value: AU $2845.00 (∼US $3004 in January 2013). This research grant was paid directly by St John of God Hospital Subiaco to the Western Australian Department of Health covering the Data Linkage Branch data extraction fees. No funding from NIH, Wellcome Trust, or Howard Hughes Medical Institute was received for this study. The authors declare no conflicts of interest. Reprints: David J. R. Morgan, MBBS, FACEM, FCICM, Department of Intensive Care, St John of God Hospital Subiaco, 12 Salvado Road Subiaco, Western Australia 6008, Australia. E-mail: [email protected]. C 2014 Wolters Kluwer Health, Inc. All rights reserved. Copyright ISSN: 0003-4932/14/26201-0086 DOI: 10.1097/SLA.0000000000000972
86 | www.annalsofsurgery.com
ongoing low complication rates and improved health expenditure cost-effectiveness. Although the data emerging around longer-term outcomes in bariatric surgery seems promising, currently published studies tend to focus primarily on enduring weight loss and obesity sequela such as diabetes with only limited reporting on long-term complications and their contributing risk factors.1,8,9 The changing landscape of contemporary bariatric surgery from open to laparoscopic procedures offers an additional expectation for reduced longterm surgical morbidity.10,11 Further acceptance of bariatric surgery as a long-term solution thus relies on the ability to corroborate that long-term complications, like short-term complications, are acceptably low and that measures of health expenditure such as reduced hospital readmission rates ensue. Where complications do arise, a better understanding of the factors that contribute to them may help inform health care providers on how to minimize these adverse outcomes further. We hypothesized that bariatric procedures are safe with a low incidence of long-term surgical and medical complications and are effective in reducing subsequent hospital readmissions by improving the complications associated with obesity. In this study, we aimed to determine the long-term outcomes, health care utilization, and risk factors for complications after bariatric surgery in the whole population of Western Australia.
METHODS Study Design and Setting This was a retrospective, observational, population-based study including all patients who underwent elective bariatric surgery in the state of Western Australia over a 5-year period between 2007 and 2011. All patients were observed until December 31, 2012, unless they died beforehand, allowing for a minimum 12-month follow-up period after bariatric surgery. In 2011, Western Australia had a population of 2.39 million, comprising 10.4% of the total Australian population.12
Data Sources This study utilized the administrative records from the Western Australian Department of Health Data Linkage Unit that systematically connects and updates all the available health data for every individual within the entire state of Western Australia. The Western Australian Data Linkage Unit brings together 8 core data elements (birth records, midwives’ notifications, cancer registrations, inpatient private and public hospital morbidity, inpatient and public outpatient mental health services data, emergency department data collection, and the Western Australian electoral roll).13,14 In addition, the death registry together with postmortem and coroners’ reports, when available, were also linked and provided the date and causes of death for those who died during the follow-up period of this study (Fig. 1). The accuracy of this database has been previously validated and formed the basis of a large number of population-based epidemiological studies in Western Australia.15,16 In addition, the techniques used by the Annals of Surgery r Volume 262, Number 1, July 2015
Copyright © 2014 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Annals of Surgery r Volume 262, Number 1, July 2015
Long-term Bariatric Outcomes and Risk Factors
FIGURE 1. Flowchart showing the inclusion of the patients and their follow-up in relation to before and after the index bariatric operation during the study period. Western Australian Data Linkage Unit to obtain linkage of health data across different jurisdictions has also been applied to other states in Australia and was found to be capable of providing high-quality data for research purposes.17 Prior approval from the Western Australian Department of Health Human Research Ethics Committee was granted before the release of de-identified data in a format using only the International Classification of Diseases, Tenth Revision (ICD-10) diagnostic and procedure codes, which were adopted throughout all Western Australian hospitals in July 1999.
Participants Participants were defined by their first elective hospital admission for bariatric surgery during the study period, and this was regarded as the index case for statistical purposes. We used the following ICD-10 procedure codes: 30511–00 (gastroplasty for morbid obesity C 2014 Wolters Kluwer Health, Inc. All rights reserved.
including gastric banding or stapling), 30511–01 (laparoscopic gastric reduction such as adjustable gastric banding, sleeve gastrectomy), 14215–00 (revision of gastric band such as addition or removal of fluid from implanted reservoir of gastric band, adjustment of gastric band, replacement of implanted reservoir of gastric band), 30512–00 (gastrojejunostomy or gastroenterostomy or gastroduodenostomy for morbid obesity, gastric reduction of gastroplasty for, by any method including anastomosis), 30512–01 (laparoscopic biliopancreatic diversion), 30512–02 (biliopancreatic diversion), 30514–00 (surgical reversal of procedure for morbid obesity), and 90950–00 (insertion of gastric bubble or balloon) together with a diagnostic code of either “obesity” or “type 2 diabetes mellitus with complications” to capture patients who had bariatric surgery for this study. A strong limitation of the ICD-10 codes is its inability to delineate between many specific bariatric procedure types, especially adjustable gastric bands www.annalsofsurgery.com | 87
Copyright © 2014 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Annals of Surgery r Volume 262, Number 1, July 2015
Morgan et al
and sleeve gastrectomies, anecdotally the 2 most common bariatric procedures in Western Australia during this time period. Patients’ comorbidity data were captured by diagnostic codes recorded in their private and public hospital admissions before the index admission for the bariatric surgery and was summarized using the Charlson Comorbidity Index.18
Variables and Outcomes Primary outcomes included health care utilization and longterm complication rates. Health care utilization was evaluated by comparing the hospital admission rates before and after index bariatric surgery for known complications of obesity (type 2 diabetes mellitus and sleep apnea) and conditions known to complicate abdominal surgery [gastrointestinal conditions, thromboembolism, sepsis, acute kidney injury (AKI), and thromboembolism]. Long-term complications compared incidence rates of all-cause and specific conditions known to complicate abdominal surgery in the postoperative period (defined in detail in the footnote of Table 2), including gastrointestinal complications, repeat bariatric surgery, sepsis, AKI, atrial fibrillation, deep vein thrombosis, and pulmonary embolism. Secondary outcomes included risk factors for long-term complications and long-term mortality rate.
Statistical Analysis Categorical variables were described in absolute numbers and percentages and continuous variables were described in mean, median, standard deviation (SD), and interquartile range (IQR). Incidences of hospitalization were presented as rate per 1000 patient-years of follow-up time, and the differences in incidence of hospitalization rates between before and after bariatric surgery were assessed by a paired t test after logarithm transformation. Multivariate logistic regression was used to assess the effects of age, Charlson Comorbidity Index, sex, and type of bariatric surgery on risk of complications after bariatric surgery, allowing nonlinearity for all continuous variables using a 3-knot restricted cubic spline function.19,20 A restricted cubic spline function is similar to a polynomial function and will allow a continuous predictor to displace a multimodal nonlinear relation (eg, U-shape or exponential) to the categorical outcome in a logistic regression model. The relative contribution of each predictor in explaining the variability in risk of complications was assessed using the χ 2 statistic minus the degrees of freedom.19,20 A sensitivity analysis was conducted after excluding patients who had bariatric surgery before the commencement of the study. All analyses were performed by SPSS for Windows (version 21, IL 2013) or S-Plus (version 8.0, 2007. Insightful Corp., Seattle, Washington, USA) with P < 0.05 being considered as significant.
RESULTS Between 2007 and 2011, there were 12,062 index cases of bariatric surgery with a mean preoperative follow-up time (±SD) of 30.4 (±16.6) months and postoperative follow-up time of 40.6 (±16.6) months after surgery (Fig. 1). Table 1 exhibits the baseline characteristics of the entire cohort. The mean age (±SD) was 43 (±11.6) years, with female patients comprising 78.4% of the total cohort. Most bariatric operations (89.9%) were performed in a private metropolitan hospital, with 94.3% of patients being either self-funded or using private health insurance to finance their surgery. Open bariatric procedures were very uncommon with laparoscopic procedures being performed in 95.1% of cases. Despite their obesity only 765 (6.3%) of patients had a Charlson Comorbidity Index 1 or more. Of the 846 patients (7.0%) who had more than 1 bariatric procedure, 174 (1.4%) had at least 1 bariatric surgery before the commencement of the study in 2007. 88 | www.annalsofsurgery.com
TABLE 1. Demographic Characteristics of All Patients Undergoing Bariatric Surgery Between 2007 and 2011 in Western Australia (n = 12,062) Follow-up, mean [SD, median, IQR], mo Proportion of female patients, no. (%) Age, mean [SD, median, IQR], yr Age groups, no. (%), yr 2
40.6 [16.6, 41, 26–54] 9451 (78.4) 43 [11.65, 43, 34–52] 4778 (39.6) 6299 (52.2) 985 (8.2) 9923 (82.3) 1449 (12.0) 581 (4.8) 102 (0.8) 7 (0.1) 174 (1.4) 368 (3.1) 11,489 (95.1) 17 (0.1) 7 (0.1) 7 (0.1) 174 (1.4) 728 (6.0) 11,297 (93.7) 641 (5.3) 124 (1.0)
∗ A complete list of all searched bariatric ICD-10 codes is contained in the methods section. †Patients who underwent their original adjustable gastric band before 2007 but had subsequent revisional bariatric surgery between 2007 and 2011. SD indicates standard deviation; IQR, interquartile range; ICD, International Classification of Diseases.
All-cause mortality after bariatric surgery was very low (n = 22,
Long-term Clinical Outcomes and Health Care Utilization After Bariatric Surgery A Population-based Study David J. R. Morgan, MBBS, FACEM, FCICM,∗ Kwok M. Ho, PhD, MPH, FANZCA, FCICM,† Jon Armstrong, MBBS, BA, FRACS,∗ and Edward Litton, MSc, MBBS, FCICM∗
Objective: To determine the long-term outcomes, health care utilization, and risk factors for complications after bariatric surgery. Background: With the burgeoning problem of obesity and the consequential rise in bariatric surgery, uncertainty remains as to whether this has been matched by a reduction in long-term health care utilization. Methods: A population-based linked-data cohort study, utilizing a comprehensive set of data, including detailed comorbidity and complications, of each individual who had undergone bariatric surgery between 2007 and 2011 in Western Australia. Records were obtained via data linkage through the Western Australian Department of Health Data Linkage Unit. Every patient was followed for a minimum of 12-months after surgery or until death. Results: A total of 12062 patients underwent bariatric surgery during the study period with a mean follow-up period of 41 months. Hospitalization rates after bariatric surgery were substantially reduced for all-cause (361 vs 501 per 1000 patient-years, P = 0.002) and diabetes mellitus–related (7 vs 31 per 1000 patient-years, P < 0.001) diagnoses when compared with hospitalization rates before bariatric surgery. Complications occurred in 2171 (18.0%) patients during the follow-up period. Patient age, sex, open surgical procedures, and Charlson Comorbidity Index were associated with an increased risk of complications, with age the most important and accounting for 77% of the variability in the risk of complications. Long-term all-cause mortality rate after surgery was extremely low (0.54 deaths per 1000 patient-years). Conclusions: When measured against long-term safety outcomes, bariatric surgery has low mortality and morbidity associated with a significant reduction in subsequent hospitalizations. Keywords: age, bariatric surgery, complications, long-term outcomes, mortality, population-based risk factors (Ann Surg 2015;262:86–92)
I
t is now regarded that bariatric surgery confers the most effective and durable treatment for obesity with an excellent short-term safety profile.1–3 With the establishment of bariatric surgery in the United States and its increasing acceptance elsewhere around the world,4–7 it is pivotal to confirm that the excellent short-term results after such surgery extend into the longer term by demonstrating
From the ∗ Department of Intensive Care Medicine, St John of God Hospital Subiaco, Western Australia, Australia; and †School of Population Health, University of Western Australia, Perth, Australia. Disclosure: St John of God Hospital Subiaco Research Grant: Sum value: AU $2845.00 (∼US $3004 in January 2013). This research grant was paid directly by St John of God Hospital Subiaco to the Western Australian Department of Health covering the Data Linkage Branch data extraction fees. No funding from NIH, Wellcome Trust, or Howard Hughes Medical Institute was received for this study. The authors declare no conflicts of interest. Reprints: David J. R. Morgan, MBBS, FACEM, FCICM, Department of Intensive Care, St John of God Hospital Subiaco, 12 Salvado Road Subiaco, Western Australia 6008, Australia. E-mail: [email protected]. C 2014 Wolters Kluwer Health, Inc. All rights reserved. Copyright ISSN: 0003-4932/14/26201-0086 DOI: 10.1097/SLA.0000000000000972
86 | www.annalsofsurgery.com
ongoing low complication rates and improved health expenditure cost-effectiveness. Although the data emerging around longer-term outcomes in bariatric surgery seems promising, currently published studies tend to focus primarily on enduring weight loss and obesity sequela such as diabetes with only limited reporting on long-term complications and their contributing risk factors.1,8,9 The changing landscape of contemporary bariatric surgery from open to laparoscopic procedures offers an additional expectation for reduced longterm surgical morbidity.10,11 Further acceptance of bariatric surgery as a long-term solution thus relies on the ability to corroborate that long-term complications, like short-term complications, are acceptably low and that measures of health expenditure such as reduced hospital readmission rates ensue. Where complications do arise, a better understanding of the factors that contribute to them may help inform health care providers on how to minimize these adverse outcomes further. We hypothesized that bariatric procedures are safe with a low incidence of long-term surgical and medical complications and are effective in reducing subsequent hospital readmissions by improving the complications associated with obesity. In this study, we aimed to determine the long-term outcomes, health care utilization, and risk factors for complications after bariatric surgery in the whole population of Western Australia.
METHODS Study Design and Setting This was a retrospective, observational, population-based study including all patients who underwent elective bariatric surgery in the state of Western Australia over a 5-year period between 2007 and 2011. All patients were observed until December 31, 2012, unless they died beforehand, allowing for a minimum 12-month follow-up period after bariatric surgery. In 2011, Western Australia had a population of 2.39 million, comprising 10.4% of the total Australian population.12
Data Sources This study utilized the administrative records from the Western Australian Department of Health Data Linkage Unit that systematically connects and updates all the available health data for every individual within the entire state of Western Australia. The Western Australian Data Linkage Unit brings together 8 core data elements (birth records, midwives’ notifications, cancer registrations, inpatient private and public hospital morbidity, inpatient and public outpatient mental health services data, emergency department data collection, and the Western Australian electoral roll).13,14 In addition, the death registry together with postmortem and coroners’ reports, when available, were also linked and provided the date and causes of death for those who died during the follow-up period of this study (Fig. 1). The accuracy of this database has been previously validated and formed the basis of a large number of population-based epidemiological studies in Western Australia.15,16 In addition, the techniques used by the Annals of Surgery r Volume 262, Number 1, July 2015
Copyright © 2014 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Annals of Surgery r Volume 262, Number 1, July 2015
Long-term Bariatric Outcomes and Risk Factors
FIGURE 1. Flowchart showing the inclusion of the patients and their follow-up in relation to before and after the index bariatric operation during the study period. Western Australian Data Linkage Unit to obtain linkage of health data across different jurisdictions has also been applied to other states in Australia and was found to be capable of providing high-quality data for research purposes.17 Prior approval from the Western Australian Department of Health Human Research Ethics Committee was granted before the release of de-identified data in a format using only the International Classification of Diseases, Tenth Revision (ICD-10) diagnostic and procedure codes, which were adopted throughout all Western Australian hospitals in July 1999.
Participants Participants were defined by their first elective hospital admission for bariatric surgery during the study period, and this was regarded as the index case for statistical purposes. We used the following ICD-10 procedure codes: 30511–00 (gastroplasty for morbid obesity C 2014 Wolters Kluwer Health, Inc. All rights reserved.
including gastric banding or stapling), 30511–01 (laparoscopic gastric reduction such as adjustable gastric banding, sleeve gastrectomy), 14215–00 (revision of gastric band such as addition or removal of fluid from implanted reservoir of gastric band, adjustment of gastric band, replacement of implanted reservoir of gastric band), 30512–00 (gastrojejunostomy or gastroenterostomy or gastroduodenostomy for morbid obesity, gastric reduction of gastroplasty for, by any method including anastomosis), 30512–01 (laparoscopic biliopancreatic diversion), 30512–02 (biliopancreatic diversion), 30514–00 (surgical reversal of procedure for morbid obesity), and 90950–00 (insertion of gastric bubble or balloon) together with a diagnostic code of either “obesity” or “type 2 diabetes mellitus with complications” to capture patients who had bariatric surgery for this study. A strong limitation of the ICD-10 codes is its inability to delineate between many specific bariatric procedure types, especially adjustable gastric bands www.annalsofsurgery.com | 87
Copyright © 2014 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.
Annals of Surgery r Volume 262, Number 1, July 2015
Morgan et al
and sleeve gastrectomies, anecdotally the 2 most common bariatric procedures in Western Australia during this time period. Patients’ comorbidity data were captured by diagnostic codes recorded in their private and public hospital admissions before the index admission for the bariatric surgery and was summarized using the Charlson Comorbidity Index.18
Variables and Outcomes Primary outcomes included health care utilization and longterm complication rates. Health care utilization was evaluated by comparing the hospital admission rates before and after index bariatric surgery for known complications of obesity (type 2 diabetes mellitus and sleep apnea) and conditions known to complicate abdominal surgery [gastrointestinal conditions, thromboembolism, sepsis, acute kidney injury (AKI), and thromboembolism]. Long-term complications compared incidence rates of all-cause and specific conditions known to complicate abdominal surgery in the postoperative period (defined in detail in the footnote of Table 2), including gastrointestinal complications, repeat bariatric surgery, sepsis, AKI, atrial fibrillation, deep vein thrombosis, and pulmonary embolism. Secondary outcomes included risk factors for long-term complications and long-term mortality rate.
Statistical Analysis Categorical variables were described in absolute numbers and percentages and continuous variables were described in mean, median, standard deviation (SD), and interquartile range (IQR). Incidences of hospitalization were presented as rate per 1000 patient-years of follow-up time, and the differences in incidence of hospitalization rates between before and after bariatric surgery were assessed by a paired t test after logarithm transformation. Multivariate logistic regression was used to assess the effects of age, Charlson Comorbidity Index, sex, and type of bariatric surgery on risk of complications after bariatric surgery, allowing nonlinearity for all continuous variables using a 3-knot restricted cubic spline function.19,20 A restricted cubic spline function is similar to a polynomial function and will allow a continuous predictor to displace a multimodal nonlinear relation (eg, U-shape or exponential) to the categorical outcome in a logistic regression model. The relative contribution of each predictor in explaining the variability in risk of complications was assessed using the χ 2 statistic minus the degrees of freedom.19,20 A sensitivity analysis was conducted after excluding patients who had bariatric surgery before the commencement of the study. All analyses were performed by SPSS for Windows (version 21, IL 2013) or S-Plus (version 8.0, 2007. Insightful Corp., Seattle, Washington, USA) with P < 0.05 being considered as significant.
RESULTS Between 2007 and 2011, there were 12,062 index cases of bariatric surgery with a mean preoperative follow-up time (±SD) of 30.4 (±16.6) months and postoperative follow-up time of 40.6 (±16.6) months after surgery (Fig. 1). Table 1 exhibits the baseline characteristics of the entire cohort. The mean age (±SD) was 43 (±11.6) years, with female patients comprising 78.4% of the total cohort. Most bariatric operations (89.9%) were performed in a private metropolitan hospital, with 94.3% of patients being either self-funded or using private health insurance to finance their surgery. Open bariatric procedures were very uncommon with laparoscopic procedures being performed in 95.1% of cases. Despite their obesity only 765 (6.3%) of patients had a Charlson Comorbidity Index 1 or more. Of the 846 patients (7.0%) who had more than 1 bariatric procedure, 174 (1.4%) had at least 1 bariatric surgery before the commencement of the study in 2007. 88 | www.annalsofsurgery.com
TABLE 1. Demographic Characteristics of All Patients Undergoing Bariatric Surgery Between 2007 and 2011 in Western Australia (n = 12,062) Follow-up, mean [SD, median, IQR], mo Proportion of female patients, no. (%) Age, mean [SD, median, IQR], yr Age groups, no. (%), yr 2
40.6 [16.6, 41, 26–54] 9451 (78.4) 43 [11.65, 43, 34–52] 4778 (39.6) 6299 (52.2) 985 (8.2) 9923 (82.3) 1449 (12.0) 581 (4.8) 102 (0.8) 7 (0.1) 174 (1.4) 368 (3.1) 11,489 (95.1) 17 (0.1) 7 (0.1) 7 (0.1) 174 (1.4) 728 (6.0) 11,297 (93.7) 641 (5.3) 124 (1.0)
∗ A complete list of all searched bariatric ICD-10 codes is contained in the methods section. †Patients who underwent their original adjustable gastric band before 2007 but had subsequent revisional bariatric surgery between 2007 and 2011. SD indicates standard deviation; IQR, interquartile range; ICD, International Classification of Diseases.
All-cause mortality after bariatric surgery was very low (n = 22,
