Flum DR, Salem L, Broeckel Elrod JA, Dellinger EP, Cheadle A, Chan L. Early Mortality Among Medicare Beneficiaries Undergoing Bariatric Surgical
Procedures. JAMA. 2005;294(15):1903-1908. doi:10.1001/jama.294.15.1903
Author Affiliations: Departments of Surgery
(Drs Flum, Salem, Broeckel Elrod, and Dellinger), Health Services (Drs Flum
and Cheadle), and Rehabilitation Medicine (Dr Chan), University of Washington,
and the Division of Clinical Standards and Quality, Centers for Medicare and
Medicaid Services, Region 10 (Dr Chan), Seattle, Wash.
Context Case series demonstrate that bariatric surgery can be performed with
a low rate of perioperative mortality (0.5%), but the rate among high-risk
patients and the community at large is unknown.
Objectives To evaluate the risk of early mortality among Medicare beneficiaries
and to determine the relative risk of death among older patients.
Design Retrospective cohort study.
Setting and Patients All fee-for-service Medicare beneficiaries, 1997-2002.
Main Outcome Measures Thirty-day, 90-day, and 1-year postsurgical all-cause mortality among
patients undergoing bariatric procedures.
Results A total of 16 155 patients underwent bariatric procedures (mean
age, 47.7 years [SD, 11.3 years]; 75.8% women). The rates of 30-day, 90-day,
and 1-year mortality were 2.0%, 2.8%, and 4.6%, respectively. Men had higher
rates of early death than women (3.7% vs 1.5%, 4.8% vs 2.1%, and 7.5% vs 3.7%
at 30 days, 90 days, and 1 year, respectively; P<.001).
Mortality rates were greater for those aged 65 years or older compared with
younger patients (4.8% vs 1.7% at 30 days, 6.9% vs 2.3% at 90 days, and 11.1%
vs 3.9% at 1 year; P<.001). After adjustment for
sex and comorbidity index, the odds of death within 90 days were 5-fold greater
for older Medicare beneficiaries (aged ≥75 years; n = 136) than
for those aged 65 to 74 years (n = 1381; odds ratio, 5.0; 95% confidence
interval, 3.1-8.0). The odds of death at 90 days were 1.6 times higher (95%
confidence interval, 1.3-2.0) for patients of surgeons with less than the
median surgical volume of bariatric procedures (among Medicare beneficiaries
during the study period) after adjusting for age, sex, and comorbidity index.
Conclusions Among Medicare beneficiaries, the risk of early death after bariatric
surgery is considerably higher than previously suggested and associated with
advancing age, male sex, and lower surgeon volume of bariatric procedures.
Patients aged 65 years or older had a substantially higher risk of death within
the early postoperative period than younger patients.
In the United States, most adults are overweight or obese,1 and
obesity is soon to become the leading cause of death. Bariatric surgical procedures
are the only interventions2 that consistently
help patients achieve significant and sustained weight loss and improvements
in comorbid medical conditions.3- 5 As
a result, there has been dramatic growth in bariatric surgery over the last
decade, with interest in applying it to those at high risk based on associated
medical conditions and the growing population of older, obese patients.6 Balanced against these beneficial effects, however,
are the risks of perioperative death and short-term adverse outcomes. These
risks have been poorly defined in the community at large, with the expected
rates largely derived from case series.4 Several
high-profile reports of death after bariatric surgery have challenged these
estimates and have triggered a critical reappraisal of bariatric surgical
Medicare, the United States’ largest health care insurer, currently
reimburses for bariatric procedures on a regional basis and is the primary
payer for approximately 20% of all procedures performed in at least 1 state.7 However, Medicare policy in this area is at a crossroads:
there is no national coverage decision and no consensus regarding the efficacy
and safety of bariatric surgery in older patients. The purpose of this study
was to determine the risk of all-cause early postsurgical mortality among
Medicare beneficiaries undergoing open bariatric surgery to help inform patients,
clinicians, insurers, and other stakeholders who are involved in medical decision
making. A secondary goal was to determine the risk of adverse outcomes among
older Medicare beneficiaries undergoing these procedures compared with that
of younger patients.
We used a retrospective cohort design, using Medicare National Claims
History Part B data from January 1, 1996, through December 31, 2002, that
contained Current Procedural Terminology (CPT) codes pertaining to bariatric surgery. The University of Washington
(Seattle) Human Subjects Review Committee (04-3527-X) approved this study.
The Medicare Part B database, maintained by the Centers for Medicare
& Medicaid Services (CMS), contains all the payment claims for the professional
component of services delivered to Medicare beneficiaries in either an inpatient
or an outpatient setting. Dates of death were obtained from the Enrollment
Database, which is obtainable from the Social Security Administration’s
database, the Master Beneficiary Record.
Patients were defined as having had bariatric surgery if they had a
claim for any of the following procedures: (1) CPT code
43842: gastric restrictive procedure without gastric bypass for morbid obesity;
vertical-banded gastroplasty; (2) CPT code 43843:
gastric restrictive procedure without gastric bypass for morbid obesity; other
than vertical-banded gastroplasty; (3) CPT code 43846:
gastric restrictive procedure with gastric bypass for morbid obesity, with
short-limbed (<100-cm) Roux-en-Y gastroenterostomy (RYGB); (4) CPT code 43847: gastric restrictive procedure with gastric bypass for
morbid obesity with small intestine reconstruction to limit absorption (including
long-limbed [≥100-cm] gastric bypass and distal bypasses such as biliopancreatic
diversion); or (5) CPT code 43848: revision of gastric
restrictive procedure for morbid obesity.
Individual surgeons were identified by their Unique Physician Identification
Number. We calculated the total number of claims for bariatric procedures
for each surgeon (1997-2002) and used this in analyses as a surrogate measure
of surgeon volume. Surgeon volume was divided into quartiles of numbers of
bariatric procedures. Surgeons with less than the median number of procedures
are referred to as lower-volume surgeons.
To adjust for potential confounding based on comorbid conditions, a
modified Charlson Comorbidity Index8 (score
range, 0-3, with 3 indicating greatest comorbidity) was calculated for each
patient based on all available claims.
The date of all-cause death was obtained from a cross-match with the
Enrollment Database performed August 14, 2004, and reported at 30 days, 90
days, and 1 year after bariatric procedure. For multivariable analyses, the
outcome of 90-day mortality was used to mark an “early” death.
Descriptive and comparative statistics were applied to compare rates
of death based on patient and surgeon characteristics. Categorical variables
were compared using Pearson χ2 statistics; continuous variables
were compared using analysis of variance.
A multivariable logistic regression model was constructed to evaluate
the odds of 90-day death based on age of 65 years or older or sex (models
1a and 1b), age of 65 years or older and sex (model
2), model 2 elements plus the Charlson Comorbidity Index (model 3), and model
3 elements plus surgeon volume (model 4), adjusting for clustering based on
surgeon using generalized estimating equations. These models were developed
using a nonparsimonious approach and including variables of clinical interest
or those demonstrated in prior studies to be potentially important (eg, sex).
Model fit was assessed using generalized Pearson residuals.9 A
secondary logistic regression model was performed to assess the differential
risk of 90-day mortality in patients older than 75 years compared with those
aged 65 to 74 years, adjusting for model 3 correlates.
To estimate the probability of death over time, Kaplan-Meier curves
were constructed. Survival was evaluated by age category (≥65 years), and
log-rank and Wilcoxon tests were used to compare unadjusted survival estimates
to determine the equality of survival curves. Rates of survival at all time
points were also compared using χ2 tests. The hazard ratio
of survival for patients aged 65 years or older compared with younger patients
was compared using multivariable Cox proportional hazard regression analyses
adjusted for clustering based on surgeon. The median follow-up was 3.4 years,
with 25% of patients followed up for 5 years or more. The longest follow-up
time was 7.7 years. Survival time was measured as the time from the index
procedure until death or August 15, 2004. The proportional hazards assumption
was confirmed by inspection of Schoenfeld residuals and log-log plotting.
Surgeon identifiers were present in 89% of cases, and analyses that
involved surgeon volume, based on number of procedures, were performed using
only complete cases. Missing data on surgeon identifiers were handled first
by assessing the degree to which the data were missing at random. Serial comparisons
of known variables were performed to determine if records missing surgeon
identifier data were measurably different from those that contained the identifiers.
We failed to identify any systematic way in which the physician identification
variable was missing, so we assumed it to be missing at random and, therefore,
we conducted a “complete case only” evaluation for multivariable
analyses and tabular evaluations of this issue. We also performed a multiple
imputation procedure for the missing surgeon volume data point and found that
this did not change our results. We also performed a sensitivity analysis
recategorizing cases with missing data as performed by surgeons with either
lower or higher volume of bariatric procedures, and this did not change the
results of the analysis.
This analysis was essentially a descriptive evaluation of mortality
rates after bariatric procedures among different groups within the Medicare
beneficiary cohort, and no a priori power calculations were performed. To
evaluate the possibility of a type II error, we determined the number of patients
needed in a 2-group evaluation of 30-day mortality rates between those younger
than 65 years and those aged least 65 years (based on a baseline rate of 2%).
Eight hundred seventy-four patients in each group of a 2-group trial would
be needed to identify a doubling of this rate (with an α level of .05
and power of 90%).
Statistical analysis was performed using Stata statistical analysis
software, version 7 (Stata Corp, College Station, Tex).
A total of 16 155 patients underwent bariatric surgical procedures
(mean age, 47.7 years [SD, 11.3 years]; 75.8% women), with 90.6% younger than
65 years (Table 1). A total of 61.2%
of cases were claims for RYGB and 19.9% were for RYGB with small intestine
reconstruction to limit absorption (distal bypass). There was more than a
3-fold increase in the number of procedures performed from 1997 (n = 1464)
to 2002 (n = 4814). The median number of bariatric procedures performed
per surgeon (among Medicare beneficiaries over the 6-year period) was 35 (interquartile
Among all patients, the rates of 30-day, 90-day, and 1-year mortality
were 2.0%, 2.8%, and 4.6%, respectively. Advancing age and male sex were associated
with early death after bariatric surgery (Table
2), with the highest rates of early mortality identified among older
men. Overall, men were much more likely to die after bariatric surgery than
women (3.7% vs 1.5%, 4.8% vs 2.1%, and 7.5% vs 3.7% for men and women at 30
days, 90 days, and 1 year, respectively; P<.001
for all time points). Mortality rates were greater for those aged 65 years
or older (n = 1517) compared with younger patients (4.8% vs 1.7%,
6.9% vs 2.3%, and 11.1% vs 3.9% at 30 days, 90 days, and 1 year, respectively; P<.001 for all time points). We found no differences
in early mortality rates between patients who had primary vs revision surgery
(2.0% vs 1.5%, 2.8% vs 2.2%, and 4.6% vs 4.3% at 30 days, 90 days, and 1 year,
respectively; all P>.10).
Higher Charlson Comorbidity Index score was associated with early death
(2.6%, 3.5%, 18.8%, and 24.7% for a Charlson score of 0-3, respectively; P<.001). Patients aged 65 years or older had a higher
Charlson Comorbidity Index score than younger patients (0.13 vs 0.06; P<.001) but there were no significant differences in
the sex distribution between these groups. After controlling for patient sex
and Charlson Comorbidity Index score (Table 3), the odds of a 90-day death were 2.8 times higher (95% confidence
interval [CI], 2.3-3.6) for patients aged 65 years or older compared with
younger patients. Similarly, after controlling for patient age and Charlson
Comorbidity Index score, the odds of death at 90 days were 2.3 times higher
(95% CI, 1.9-2.7) for men than for women. The relationship of age and adverse
outcome was stronger among older beneficiaries. The odds of death within 90
days of the operation were 5 times greater for patients aged 75 years or older
than for those aged 65 to 74 years (95% CI, 3.1-8.0) after adjustment for
sex, Charlson Comorbidity Index score, and surgeon volume.
Patients undergoing procedures by surgeons with lower volume of bariatric
procedures (less than the median of surgical volume among Medicare beneficiaries
between 1997-2003) had a higher rate of mortality than those with at least
median experience (3.3% vs 2.0%; P<.001). Patients
aged 65 years or older had much higher rates of early death when undergoing
surgery by surgeons within the lowest quartile of volume (Table 4) compared with those in the highest quartile (9% vs 1.1%
at 30 days and 13.8% vs 1.1% at 90 days; P<.001).
Surgeons in the highest quartile of bariatric procedure volume had similar
rates of early mortality in both younger and older patients (1.8% 90-day mortality
in patients <65 years and 1.1% mortality in patients ≥65 years; P = .40). The higher overall rates of death among
older patients were attributable in part to a higher proportion (36%) of older
patients undergoing surgery by surgeons within the lowest quartile of bariatric
surgery volume compared with younger patients. The odds of a 90-day death
were 1.6 times higher for patients of surgeons with lower volume (less than
the median) after adjusting for age, sex, and Charlson Comorbidity Index score
(95% CI, 1.3-2.0).
The hazard ratio for death (Figure)
at any time after the procedure was 2.3 times greater for patients aged 65
years or older compared with younger patients (95% CI, 2.0-2.7), with 9.5%
5-year mortality in younger patients compared with 21.6% mortality in the
older cohort (P<.001). The odds of 90-day death
did not change significantly based on the year the procedure was performed,
even after controlling for patient age, sex, and Charlson Comorbidity Index
score (odds ratio, 1.0; 95% CI, 0.9-1.0).
This study of the complete, nationwide fee-for-service Medicare population
undergoing bariatric surgery from 1997 through 2002 found that the early risk
of postsurgical death in this population was higher than suggested by prior
series. We also identified strong associations between the risk of early death
and advancing age, male sex, and surgeon procedural volume.
While at least 1 case series10 has reported
no early deaths following bariatric procedures among elderly patients, most
have found higher mortality rates compared with younger patients.11- 14 Our
study demonstrates that in the community at large, patients aged 65 years
or older face a nearly 3-fold increase in the risk of early mortality. This
absolute mortality risk (4.8% within 30 days) is more than double the risk
of mortality associated with coronary revascularization (≈2%)15 or
hip replacement (≈1%),16 2 procedures commonly
performed in older patients. There may be several reasons for these findings.
Older patients do not tolerate surgical stress as well as younger patients17 and may also have less benefit after surgery than
younger patients because much of the impact of obesity on organ systems, such
as the heart,18 may have occurred by the time
of the operation. It also remains to be seen if surgical weight loss in older
patients decreases utilization of health care resources,19 improves
functional status and quality of life,20 or
extends survival7,21,22 as
has been suggested in studies of younger patients.
Other studies have demonstrated that men have a higher rate of death
and adverse outcome7,12,23 following
bariatric surgery. In 1 retrospective series12 of
1067 patients undergoing RYGB, men had more than a 3-fold higher mortality
rate than women, even after controlling for body mass index differences. In
our previous study of nearly 3000 patients undergoing RYGB in the state of
Washington, men had a 2.3-fold increased odds of death, even after adjustment
for comorbid conditions.7 Further studies are
necessary to better understand why postoperative mortality rates are significantly
higher in men. The fact that this effect persists even after controlling for
body mass index and comorbid conditions suggests that unmeasured characteristics
associated with men (eg, body composition, occult heart disease, diminished
physiologic tolerance to stress) may be involved. Among the youngest subgroup
of patients evaluated in our study (<25 years), we found fewer differences
in death rates between men and women.
Another important factor linked to early postoperative death and adverse
outcomes following bariatric surgery is surgeon7 and
hospital procedural volume.24,25 In
the state of Washington, patients whose surgeons had performed fewer than
20 procedures had a 4.7-fold increased risk of death at 30 days.7 Among
a large, multistate collaborative of teaching hospitals, institutions where
fewer than 50 procedures were performed per year had the highest rates of
in-hospital mortality (1.2% compared with 0.3% in higher-volume [>100 cases]
hospitals).25 In the state of Pennsylvania,
patients of surgeons who performed fewer than 50 cases per year in low-volume
(<50 cases per year) hospitals had the highest rates of adverse outcomes.
This suggests an additive effect of surgeon and institutional volumes.24
The interaction of advanced age of the patient and surgical volumes
may be a particularly important influence on the risk of adverse outcomes.
In the teaching hospital series,25 mortality
rates among patients older than 55 years were 3 times greater at low-volume
hospitals. Despite finding higher-than-expected rates of overall mortality
among older patients, our study clearly demonstrates similarly low mortality
rates for older and younger Medicare beneficiaries who undergo procedures
by surgeons with the highest procedural volume. This study helps to demonstrate
that bariatric surgery is not necessarily a higher-risk procedure among those
aged 65 years or older. The specific processes of care, elements of surgical
training, or patient selection used by surgeons who perform higher volumes
of bariatric procedures should be further investigated.
This study has several limitations. While a proportion of the cases
included in this analysis may have been performed laparoscopically, we cannot
be certain when the laparoscopic procedure was performed or if laparoscopic
procedures were excluded by this analysis. While all procedural codes that
explicitly describe surgical procedures for the treatment of morbid obesity
were used to define this cohort, until January 2005 there was no discrete
code for laparoscopic bariatric procedures. Until this new code was activated,
billing personnel variably used the code 43659 (“unlisted laparoscopic
procedure stomach”) or “open” codes for those procedures.
Unfortunately, the unlisted code was not exclusively used for the purposes
of laparoscopic bariatric procedures and included procedures such as laparoscopic
excision of a gastric mass and laparoscopic repair of a perforated ulcer.
Given the possibility that this code might not refer to bariatric surgerical
procedures (and an inability to absolutely distinguish it from other procedures),
we elected to exclude this claim from the cohort definition. We considered
the possibility that patients undergoing laparoscopic procedures were at lower
risk of death than those undergoing the open procedure as a result of patient,
surgeon, or hospital selection. In that case, excluding laparoscopic cases
from the analysis might have created a cohort of patients at progressively
greater risk for death as the study period advanced and the proportion of
all procedures performed laparoscopically increased. However, we found no
differences in mortality rates over time, and, barring a countervailing trend
of outcome improvement with open bariatric surgery, we would have expected
to see the mortality rate increase if the cohort was becoming progressively
higher-risk over time.
An additional limitation is that because the CMS cohort includes all
patients aged 65 years or older but only medically disabled patients younger
than 65 years, comparisons of outcome between those aged 65 years or older
and younger patients may be biased. Medically disabled patients younger than
65 years may have a higher burden of comorbid conditions than older patients
and this might be expected to act as a conservative bias in that we demonstrate
a comparatively worse outcome in the older population.
Morbid obesity itself is not an indication for a disability claim in
the CMS system; rather, a specific disabling condition is required for coverage.
This data set does not provide information to help determine if obesity-related
comorbid conditions were the reason patients were provided coverage based
on disability. In practice, a group of conditions related to extreme obesity
are often the justification for these disability claims. These conditions
include debilitating osteoarthritis, depression, peripheral edema, and hypoventilation
Another limitation of this analysis is that the measure for surgeon
volume only counts procedures performed among CMS beneficiaries and begins
after 1996. These would tend to underestimate surgeons’ procedure volume
if they had performed any procedures outside of CMS or before the study period.
This might have acted as a conservative bias given our findings linking surgeon
inexperience to adverse outcomes, but surgeons who perform more procedures
among CMS beneficiaries may be different in other ways than other surgeons.
We also used number of bariatric procedures to evaluate the relationship
of surgeon volume and outcome because in evaluations of other abdominal operations,26 “hospital volume” effects are largely
related to “surgeon volume” effects and, when available, surgeon
volume may be the more direct and, therefore, appropriate measure of outcome
that relates to technical factors. While multidisciplinary care and other
hospital resources may play a role in adverse outcome, we did not assess this
effect in these outcomes. Last, surgeon identifiers used to derive the volume
variable were missing in approximately 11% of cases and a complete-case-only
analysis was performed for relevant evaluations. Complete and incomplete cases
were compared and found in all other ways to be similar but the possibility
that cases with missing data were different in other ways from cases with
complete data cannot be excluded.
In conclusion, this study found that the risk of early postsurgical
death among Medicare beneficiaries undergoing bariatric surgery was considerably
higher than prior case series have suggested and was strongly associated with
advancing age, male sex, and lower surgeon volume. Those considering the role
of bariatric procedures in older patients should balance this population-level
risk of adverse outcomes against the anticipated benefits of the procedure.
Directing care of older patients to surgeons who perform higher volume of
bariatric procedures in Medicare beneficiaries might be expected to improve
outcomes in this high-risk population.
Corresponding Author: David R. Flum, MD,
MPH, Department of Surgery, University of Washington, Box 356410, 1959 NE
Pacific St, Seattle, WA 98195-7183 (email@example.com).
Author Contributions: Dr Flum had full access
to all of the data in the study and takes responsibility for the integrity
of the data and the accuracy of the data analysis.
Study concept and design: Flum, Dellinger,
Acquisition of data: Flum, Salem, Dellinger,
Analysis and interpretation of data: Flum,
Broeckel Elrod, Dellinger, Cheadle, Chan.
Drafting of the manuscript: Flum, Dellinger,
Critical revision of the manuscript for important
intellectual content: Flum, Salem, Broeckel Elrod, Dellinger, Cheadle,
Statistical analysis: Flum, Dellinger, Cheadle,
Obtained funding: Flum, Salem.
Administrative, technical, or material support:
Flum, Broeckel Elrod, Dellinger, Chan.
Study supervision: Flum, Chan.
Financial Disclosures: None reported.
Funding/Support: This work was funded in part
by National Institute of Diabetes and Digestive and Kidney Diseases grants
1UO1DK066568-01 and R21 DK069677-01.
Role of the Sponsor: The study’s sponsor
had no role in the design and conduct of the study, in the collection, analysis,
and interpretation of the data, or in the preparation, review, or approval
of the manuscript.
Disclaimer: The views expressed in this article
are those of the authors and not necessarily those of the Centers for Medicare
and Medicaid Services or the University of Washington. Dr Flum was not involved
in the editorial evaluation or decision to publish this article.