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Santry HP, Gillen DL, Lauderdale DS. Trends in Bariatric Surgical Procedures. JAMA. 2005;294(15):1909–1917. doi:10.1001/jama.294.15.1909
Context The increasing prevalence and associated sociodemographic disparities
of morbid obesity are serious public health concerns. Bariatric surgical procedures
provide greater and more durable weight reduction than behavioral and pharmacological
interventions for morbid obesity.
Objective To examine trends for elective bariatric surgical procedures, patient
characteristics, and in-hospital complications from 1998 to 2003 in the United
Design, Setting, and Patients The Nationwide Inpatient Sample was used to identify bariatric surgery
admissions from 1998-2002 (with preliminary data for 12 states from 2003)
using International Classification of Diseases, Ninth Revision, codes for foregut surgery with a confirmatory diagnosis of obesity
or by diagnosis related group code for obesity surgery. Annual estimates and
trends were determined for procedures, patient characteristics, and adjusted
Main Outcome Measures Trends in bariatric surgical procedures, patient characteristics, and
Results The estimated number of bariatric surgical procedures increased from
13 365 in 1998 to 72 177 in 2002 (P<.001).
Based on preliminary state-level data (1998-2003), the number of bariatric
surgical procedures is projected to be 102 794 in 2003. Gastric bypass
procedures accounted for more than 80% of all bariatric surgical procedures.
From 1998 to 2002, there were upward trends in the proportion of females (81%
to 84%; P = .003), privately insured patients
(75% to 83%; P = .001), patients from ZIP
code areas with highest annual household income (32% to 60%, P<.001), and patients aged 50 to 64 years (15% to 24%; P<.001). Length of stay decreased from 4.5 days in 1998 to 3.3 days
in 2002 (P<.001). The adjusted in-hospital mortality
rate ranged from 0.1% to 0.2%. The rates of unexpected reoperations for surgical
complications ranged from 6% to 9% and pulmonary complications ranged from
4% to 7%. Rates of other in-hospital complications were low.
Conclusions These findings suggest that use of bariatric surgical procedures increased
substantially from 1998 to 2003, while rates of in-hospital complications
were stable and length of stay decreased. However, disparities in the use
of these procedures, with disproportionate and increasing use among women,
those with private insurance, and those in wealthier ZIP code areas should
be explored further.
Morbid obesity is an increasing health problem in the United States.
In 2002, 5.1% of US adults had a body mass index (BMI) higher than 40.1 The prevalence of individuals with a BMI higher than
40 quadrupled from 1:200 in 1986 to 1:50 in 2000; the prevalence of individuals
with a BMI higher than 50 quintupled from 1:2000 to 1:400.2 Morbid
obesity is associated with adverse health conditions and early mortality,3-6 and causes
psychosocial and quality of life detriments.7-9 Livingston
and Ko10 found significantly higher proportions
for black race, lower education and income levels, and reliance on Medicaid
among morbidly obese individuals in the United States. The increasing prevalence
and associated sociodemographic disparities of morbid obesity are serious
public health concerns.
In 1991, a National Institutes of Health Consensus Statement established
guidelines for gastric bypass surgery and vertical banded gastroplasty for
the treatment of morbid obesity (BMI of 35-40 with comorbidities or BMI >40).11 Bariatric surgery remains the only durable option
for weight loss in the morbidly obese.12 However,
bariatric surgery has changed dramatically since 1991 due to the increase
in the prevalence of morbid obesity, the advent of new procedures, and growing
demand for surgery.13-15
Pope et al16 reported that total bariatric
surgical procedures in the United States increased from 4925 in 1990 to 12 541
in 1997 and recently reported a continued increase to approximately 41 000
procedures in 2000.17 The American Society
for Bariatric Surgery estimates that its members performed 63 000 bariatric
surgical procedures nationwide in 2002, suggesting that growth in bariatric
procedures has been much greater in recent years.14
In this study, we examined recent national population-based trends in
bariatric surgical procedures, patient characteristics, and in-hospital complications.
In particular, we wanted to determine trends in newer techniques, in patient
sociodemographic characteristics and comorbidities, and in surgical complications
due to these procedural and patient population changes.
We used the Nationwide Inpatient Sample (NIS) from the Healthcare Cost
and Utilization Project. It is the largest all-payer inpatient database in
the United States. The NIS represents a 20% stratified sample of inpatient
admissions to acute care hospitals nationwide (excludes federal and prison
hospitals). Stratification is based on hospital region, urban/rural location,
teaching status, number of beds, and ownership. Sampling weights are provided
for accurate calculations based on the complex survey design. We obtained
data from the most recent years available (1998 to 2002). Preliminary data
were available for 2003 for some states via the Healthcare Cost and Utilization
Project online query system. The NIS is publicly available and contains no
personal identifying information; therefore, this study was exempt from institutional
review board approval.
The International Classification of Diseases, Ninth
Revision (ICD-9),18 coding system does
not have specific codes for all procedures currently performed for weight
loss. We consulted previous studies and the Centers for Medicare & Medicaid
Services’ billing guidelines to develop a thorough list of ICD-9 codes to identify bariatric procedures.10,16,17,19-24 We
relied on both a procedure code(s) for foregut surgery (43.0-44.99, 45.50-45.91)
and a confirmatory diagnosis code for obesity (278.00-278.8) or a diagnosis
related group code for obesity surgery (288). We excluded observations that
were unlikely for elective weight-loss procedures based on diagnosis codes
for gastrointestinal tract neoplasm (150.0-159.9), inflammatory bowel disease
(555.0-556.9), or noninfectious colitis (557.0-558.9), and emergent admission
codes (admission-type variable = emergent or urgent and/or admission-source
variable = emergency department or other hospital).
In the ICD-9, there is no code for laparoscopic
bariatric surgery, so we explored whether the code for laparoscopy (54.21)
would capture laparoscopic procedures. However, too few cases were identified
to be plausible; therefore, we did not analyze laparoscopy further. Procedures
were grouped by codes into 5 categories: gastric bypass, gastroplasty (vertical
banded gastroplasty and adjustable gastric banding), malabsorptive (duodenal
switch, biliopancreatic diversion, and isolated intestinal bypass), gastrectomy
(all types of partial gastrectomies), and other (nonspecified gastric procedures
and gastric bubble insertion) (Table 1).
Patient data included age, race, sex, and type of insurance. Average
annual household income in the patient’s ZIP code of residence (adjusted
for inflation based on projections of the 1990 census; hereafter referred
to as ZIP code level income) was reported in the NIS in 4 strata: less than
$24 999, $25 000 to $34 999, $35 000 to $44 999,
and more than $45 000. Based on 15 diagnosis codes (ICD-9 )
included in the data, we calculated a comorbidity index using the Deyo adaptation25 of the Charlson Weighted Index of Comorbidity, a
validated measure for use with administrative data that correlates with in-hospital
morbidity and mortality.
Each state participating in the Healthcare Cost and Utilization Project
had its own race classification schema or systematically did not report race.
The Healthcare Cost and Utilization Project then created a uniform race variable,
the categories of which were used for our data analysis. We attempted to analyze
data to explore our hypothesis that racial disparities exist in the receipt
of bariatric surgery. Unfortunately, due to the large amount of missing race
data (21%-34%), this was not possible. However, for the purposes of multivariable
analyses, race was included as an independent variable with missing race used
as a separate category.
After reviewing recent studies,26-36 we
classified complications that occurred during admissions for a bariatric surgical
procedure by codes into 2 categories: technical and systemic. Technical complications
included unexpected reoperations for surgical complications, splenic injury,
hemorrhage, anastomotic leaks, and wound complications. Systemic complications
included respiratory tract, cardiac, neurological, thromboembolic, genitourinary
tract, and multisystem (shock) complications. Mortality was available directly
from the data set (Table 1).
Our primary outcomes of interest were types of bariatric procedures,
patient characteristics, in-hospital complications, and length of stay. In
our statistical analysis, we calculated frequencies of these outcomes for
each year and determined if there were any trends in outcomes from 1998 to
2002. The complex survey design of the NIS prohibited conducting these analyses
in a single step because sampling weights are changed annually to reflect
increases in state participation. Collapsing multiyear data with varying sampling
weights into a single data set results in invalid annual point and variance
estimates and consequently invalid tests for trends across years.
Therefore, we first determined the frequency of each outcome for each
year separately. We used sampling weights, strata, and primary sampling units
unique to each year of the data to produce statistically valid point estimates
and variances using the Taylor expansion method.37 Point
estimates and variances for complications were adjusted for patient age, race,
sex, Charlson Index, type of insurance, and ZIP code level income using multiple
logistic regression with SAS software version 9.1 (SAS Institute Inc, Cary,
A simple test for trend based on point estimates alone ignores the fact
that each estimate has an associated variance reflecting its sampling weight
in the survey design. To analyze trends using the annual point estimates and
variances previously calculated, we wrote a program using STATA software version
8 (STATA Corp, College Station, Tex) to perform the Cochran-Armitage test
for trend38 across all 5 years of data. To
achieve statistical significance, the test required both the point estimates
and associated variances for the outcomes of interest to display a consistent
linear relationship over time.
Calculating this test for trend was more complicated when examining
trends in adjusted complication rates because of simultaneous trends in patient
characteristics. Therefore, after determining the annual adjusted complication
rates based on each year’s case mix, we standardized complication rates
to the 1998 patient characteristic modal values. Point estimates and variances
of these standardized rates were then used to perform a valid test for trend.
Trend tests were considered statistically significant at P<.05.
Although the NIS varies its sampling design annually so that data are
nationally representative despite increasing state participation each year,
we were concerned that trends may have been influenced by factors unique to
states new to the NIS from 1998 to 2002. We repeated all estimates and statistical
tests using data from 22 states that were continuously in the NIS from 1998
to 2002. No significant differences were found. The results presented herein
include all states in the NIS.
The entire 2003 NIS data have not been released yet, but some state-level
2003 data are available online (http://www.ahrq.gov/data/hcup/).
Using Healthcare Cost and Utilization Project online query system, we obtained
estimates of the total number of procedures as well as patient age, sex, and
type of insurance for 12 states (Arizona, Colorado, Florida, Hawaii, Iowa,
Massachusetts, New Jersey, New York, Oregon, South Carolina, Utah, Washington)
that were continuously in the NIS from 1998 through 2003. These data (hereafter
referred to as state-level data) allowed us to track the number of procedures
and trends in age, sex, and type of insurance in these states through 2003
and to project a national total for 2003.
The estimated number of bariatric surgical procedures increased from
13 365 in 1998 to 72 177 in 2002 (P<.001).
Based on state-level data, this number is projected to be 102 794 in
2003 (Figure). Gastric bypass was the
most commonly performed bariatric surgical procedure, accounting for 80% to
90% of all procedures during the study period (Table 2). The proportion of gastroplasty procedures decreased from
25% in 1998 to 7% in 2002 (P = .01). Proportions
of other procedures did not change significantly although absolute numbers
Trends in patient characteristics appear in Table 3. Mean (SD) age increased from 39.6 (0.28) to 41.7 (0.21)
years (P<.001), with an increase in the proportion
of patients aged 50 to 64 years and a decrease in the proportion of patients
aged 18 to 49 years. The proportion of adolescent patients (<18 years)
was low and the proportion of elderly patients (>64 years) was stable. Between
1998 and 2003, state-level data showed an upward trend in the proportion of
patients aged 45 to 64 years from 36% to 42% (P = .03;
data not shown). The majority of patients were female nationally and in state-level
data; nationwide the proportion of female patients increased from 81% in 1998
to 84% in 2002 (P = .003). Based on the
Charlson Index, the proportion of patients without comorbidities decreased
from 71% to 64% (P = .001). The proportion
of patients with only 1 comorbidity increased from 23% to 29% (P<.001), but there were no changes in the proportion of patients
with more than 1 comorbidity.
The proportion of patients with the highest ZIP code level income (>$44 999
per year) increased from 32% to 60% (P<.001).
Proportions of all other ZIP code level income groups decreased. The proportion
of patients with private insurance increased from 75% to 83% (P = .001), while proportions of patients with Medicare and
Medicaid decreased from 9% to 6% (P = .003)
and from 7% to 5% (P = .05), respectively.
State-level data showed the proportion of Medicaid patients declined from
10% to 7% between 1998 and 2003 (P = .03;
data not shown) and the proportion of privately insured patients increased
from 60% to 77% (P = .04; data not shown).
The proportion of self-pay patients was stable.
Trends in adjusted and standardized in-hospital complications appear
in Table 4. The standardized in-hospital
mortality rate was stable between 0.1% and 0.2%. Standardized mean length
of stay decreased from 4.5 days to 3.3 days (P<.001).
There were no trends in technical complications, which occurred in 1% to 2%
of admissions. Standardized rates of unexpected reoperations for surgical
complications during the same admission ranged from 6% to 9%. The most frequent
systemic complications were pulmonary and occurred in 4% to 7% of admissions.
Rates of other complications were low and stable.
These data suggest that the estimated number of bariatric surgical procedures
has increased markedly from 13 365 in 1998 to a projected 102 794
in 2003. Recent growth was substantially higher than that previously reported.16,17,21
Encinosa et al39 recently analyzed the
costs associated with this increase in bariatric procedures and found increasing
costs despite decreasing lengths of stay and fewer complications. If our observed
rate of growth continues, there will be approximately 130 000 bariatric
procedures in 2005 and as many as 218 000 in 2010. The cost to the US
health care system will be substantial. However, in the absence of a nonsurgical
option for morbid obesity, our findings regarding in-hospital safety of bariatric
surgery are promising while our findings regarding worsening sociodemographic
disparities are worrisome.
Similar to previous studies,16,17,21 we
found gastric bypass to be the predominant procedure. Because adjustable gastric
banding was approved in the United States in 2001 and there was no code to
separate it from vertical banded gastroplasty, we had expected an increase
in gastroplasty procedures in 2001; instead, the proportion of gastroplasty
procedures decreased during this period. National studies previously examining
gastric bypass and gastroplasty procedures found trends toward increasing
proportions of gastric bypass.16,17 However,
when we measured malabsorptive procedures and isolated gastrectomies, the
proportion of gastric bypass procedures remained stable, suggesting that newer
procedures were filling the gap between gastric bypass and gastroplasty from
1998 to 2002. We are aware of only 1 previous national study that also attempted
to capture malabsorptive procedures21; however,
that study did not describe trends in their proportions, which we found to
Patients undergoing bariatric surgical procedures were overwhelmingly
female and the trend continued to increase during our study period. This is
similar to findings in Wisconsin and North Carolina that rates of women undergoing
bariatric surgery in the late 1990s to 2001 far outpaced those of men.23,24 Using cross-sectional data from 2000,
Livingston and Ko10 found that 36% of US adults
meeting current BMI criteria for bariatric surgery were male. However, fewer
than 20% of patients during our study period were male. Trus et al17 did not observe sex-based trends in bariatric surgery
use between 1990 and 2000. This suggests that our observation is due to increases
in the proportion of female patients since 2000 and may be attributable to
a greater popularity of newer techniques among women.
Despite controversy over bariatric surgery for adolescent and elderly
patients, each accounted for a small and stable proportion of patients. Overall,
we demonstrated a shift toward higher risk patients in terms of both older
age and higher comorbidities. Individuals aged 50 to 64 years were increasingly
likely to undergo surgery during our study period. Other investigators17,22,40 have found a trend
toward increasing average age of bariatric surgery patients; our results suggest
this is due to increases among the oldest age group (50-64 years). We also
found that patients were increasingly likely to have at least 1 comorbidity
in the Charlson Index, an observation previously made in the data from a single
Bariatric surgery is not a regulated or credentialed surgical subspecialty.
With the expanding pool of prospective patients and profitability of bariatric
surgical procedures,14 surgeons and hospitals
have been offering weight loss surgeries without accurate methods of tracking
surgeons, procedural volume, patient characteristics, and postoperative complications.
Despite a shift toward higher risk patients, we did not find increases
in in-hospital morbidity or mortality. We had anticipated that complication
rates might increase as surgeons and hospitals operated at rates exceeding
the learning curve for bariatric surgical procedures. Bariatric surgery is
elective, and morbid obesity, despite associated adverse medical and social
consequences, is not an immediate surgical indication. Therefore, even small
increases in complication rates would have been clinically significant. Although
rates of unexpected reoperations for surgical complications were substantial
(7%-9%), mortality and rates of other technical and systemic complications
were low and remained stable or improved during our study period. We did,
however, find a decrease in length of stay. Because our study was based on
in-hospital data, it is possible that some complications were not measured
due to earlier discharge.
Although we could not assess racial trends, we did find evidence suggesting
increasing socioeconomic disparities based on insurance status and ZIP code
level income. Zhang and Wang41 had previously
identified an inverse relationship between socioeconomic status and obesity.
We found the opposite relationship between socioeconomic status and bariatric
surgery use. Fewer than 5% of patients lived in ZIP code areas with average
household incomes of less than $25 000 per year, and this proportion
was decreasing. Meanwhile, the proportion of patients who lived in ZIP code
areas with average household incomes of more than $44 999 per year increased
to 60% in 2002.
Parallel trends were noted based on type of insurance. In both national
and state-level data, the overwhelming majority of patients had private insurance
and this proportion increased. In contrast, the proportion of Medicaid patients
made up less than 10% of the patient population and this proportion was decreasing.
These trends toward patients in higher socioeconomic groups based on ZIP code
level income and type of insurance were in contrast to Livingston and Ko’s
findings that 28% of morbidly obese US adults in 2000 earned less than $20 000
per year and that 12% were in the Medicaid program.10 It
is possible that these disparities are the result of overuse of bariatric
surgery among higher socioeconomic groups rather than underuse among lower
socioeconomic groups. However, our finding that the socioeconomic profile
of bariatric surgery patients increasingly did not reflect the socioeconomic
profile of individuals with morbid obesity requires further study.
Our study has several important limitations. First, our results are
estimates based on a large, complex survey sample. In the absence of a national
bariatric surgery registry, administrative data are the only source for national
population-based trends in bariatric surgery and the NIS represents the best
available data source given its sophisticated sampling design and large number
of observations. Our estimates were derived from 2713 bariatric surgery patients
in 1998; 4595 in 1999; 6563 in 2000; 11 347 in 2001; and 14 926
in 2002. These numbers exceed most currently available clinical series and
are weighted to provide national estimates.
Second, we relied on ICD-9 codes to capture
bariatric surgery admissions; however, procedural innovation during the study
period outpaced ICD-9 coding. Although laparoscopy
has been widely performed since the late 1990s, like other investigators,42 we were unable to identify laparoscopic procedures
with certainty. Similarly, we could not distinguish between vertical banded
gastroplasty (introduced in 1980) and adjustable gastric banding (approved
in 2001). To identify malabsorptive procedures, we had to combine multiple
codes. Future research using administrative data will benefit from the use
of more specific procedure codes in the International Statistical
Classification of Diseases, 10th Revision.
Third, the administrative data we used cannot assess the benchmark 30-day
morbidity and mortality used to measure perioperative safety in clinical series.
All personal identifying information is eliminated to protect the confidentiality
of patients included in the NIS. Therefore, we were unable to link our findings
to vital statistics or follow-up hospitalizations. A study by Flum and Dellinger19 linked administrative data from Washington with vital
statistics, and found a 2% rate of 30-day mortality after bariatric surgery.
This rate exceeds the mortality in most published clinical series by almost
4-fold and is 5 to 10 times higher than our in-hospital estimates. However,
we assessed a thorough list of acute complications occurring over a 5-year
period after a variety of bariatric procedures. Carbonell et al42 conducted
a 1-year, unweighted, cross-sectional analysis of complications that was limited
to gastric bypass admissions. Two previous studies16,17 of
trends in complications were limited to gastric bypass and vertical banded
gastroplasty. Another study that also included malabsorptive procedures grouped
together admissions over a 5-year period and did not examine trends.21 Our description of the most recent population-based
trends of in-hospital complications complements recent meta-analyses43,44 describing the long-term efficacy
of bariatric surgery, and provides timely and important data for policymakers
and insurance providers who are currently debating the safety of bariatric
Fourth, our study was limited by the variables in the data set. As in
other studies using the NIS,16,45-47 we
could not examine patient race because some states in the NIS systematically
do not report race and, among those that do, 20% of observations are missing
race data. Given the well-documented racial disparities in the prevalence
of obesity,1,48-52 data
on race of bariatric surgery patients may have had significant implications.
Our conclusions about patient socioeconomic status are based on type of insurance
and a proxy for household income. The NIS reports income using 4 strata based
on the average annual household income in the patient’s area of residence,
a proxy measure that may result in misclassification. However, we found that
private insurance and higher ZIP code level income were highly correlated.
Fifth, the NIS does not include BMI or obesity-related comorbidities
(sleep apnea, osteoarthritis, etc), which are not captured well in administrative
data. Therefore, although we did find an increase in comorbidities using the
Deyo adaptation of the Charlson Index, we did not have enough clinical information
to describe trends in surgical indications or obesity-related health conditions.
Moreover, most patients in this study had no comorbid conditions (Charlson
Index of 0), which may reflect incomplete coding and limits inferences about
trends in comorbidity. These coding limitations are common to administrative
data, but the NIS remains the best and most current source for nationwide
population-based trends in bariatric surgery.
In light of our finding that in-hospital morbidity and mortality appeared
stable or improved despite higher risk patients, recent data on the long-term
efficacy of surgery,43,44,53 and
increasing consensus that surgery is the only effective long-term treatment
for morbid obesity,53-56 our
findings that bariatric surgery patients were more likely to be women from
higher socioeconomic groups are concerning. State-level data through 2003
suggested that these latter disparities may have worsened. Disproportionate
sociocultural pressures to be thin may explain the imbalance between men and
women undergoing an elective procedure for weight loss. Type of insurance
coverage also may play a role in socioeconomic disparities.
During our entire study period, the Center for Medicare & Medicaid
Services covered bariatric surgical procedures for patients with both a BMI
higher than 35 and obesity-related comorbidities. The Center for Medicare
& Medicaid Services has recently changed its policies to include patients
with a BMI higher than 40, but without obesity-related comorbidities.56 This decision may increase bariatric surgery use
among Medicaid patients. However, many US individuals from low-income groups
do not qualify for Medicaid; it is unlikely that the changes in coverage by
the Center for Medicare & Medicaid Services alone will improve the socioeconomic
disparities we found. Other sources of disparities include the possibility
that cultural attitudes toward morbid obesity may differ by socioeconomic
status, that primary care physicians may be less likely to refer patients
of lower socioeconomic status for bariatric surgery, or that hospitals providing
bariatric surgery may be less accessible to lower socioeconomic groups.
The field of bariatric surgery has changed dramatically in the 14 years
since the National Institutes of Health Consensus Conference statement11 and these 1991 guidelines are being reexamined. As
bariatric surgeons continue to improve procedures for weight loss, researchers
and policymakers should examine factors associated with the uneven use of
bariatric surgery. They also should study the impact of the media, cultural
beliefs about body weight and health, patient socioeconomic status, and surgeon
motivations on the rapid growth of bariatric surgery and differential use
rates. Public health campaigns focusing on the health dangers of obesity may
help shift thinking about obesity from a cosmetic concern of women to a health
concern for both sexes.
With increased knowledge of bariatric surgery indications, risks, and
benefits among health care professionals, bariatric surgery is likely to become
the standard of care for morbidly obese individuals. Together, these changes
should lead to more morbidly obese patients of both sexes and all socioeconomic
groups seeking surgery. Although preventing obesity should remain the focus
of US health care, efforts must be made to ensure equal access to bariatric
surgery irrespective of sex and socioeconomic status for those who are morbidly
obese, have an indication for surgical intervention, and wish to undergo an
elective surgical procedure to improve health, longevity, and quality of life.
Corresponding Author: Heena P. Santry, MD,
5841 S Maryland Ave, MC 6040, Chicago, IL 60637 (firstname.lastname@example.org).
Author Contributions: Dr Santry 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: Santry, Gillen, Lauderdale.
Acquisition of data: Santry.
Analysis and interpretation of data: Santry,
Drafting of the manuscript: Santry.
Critical revision of the manuscript for important
intellectual content: Gillen, Lauderdale.
Statistical analysis: Santry, Gillen.
Obtained funding: Santry.
Administrative, technical, or material support:
Study supervision: Lauderdale.
Financial Disclosures: None reported.
Funding/Support: Dr Santry was supported by
a fellowship from the Robert Wood Johnson Clinical Scholars Program, a pilot
project grant (P30 AG-12857-08) from the National Institute on Aging to the
Center on Aging at the University of Chicago, and the Dr Paul Jordan Research
Fund in Surgery at the University of Chicago.
Role of the Sponsor: Neither the Robert Wood
Johnson Foundation nor the National Institute on Aging played any role in
the design and conduct of the study; collection, management, analysis, and
interpretation of the data; and preparation, review, or approval of the manuscript.
Disclaimer: The authors of this article are
responsible for its contents. No statement in this article should be construed
as an official position of the Agency for Healthcare Research and Quality
or the US Department of Health and Human Services.
Previous Presentations: Abstract of preliminary
data presented at the 11th Annual Charles Huggins Research Conference, Chicago,
Ill, May 15, 2004. Abstract presented at the Chicago Surgical Society, Chicago,
Ill, March 3, 2005.
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