Supplementary Table 3: Access to bariatric surgery by socioeconomic status (SES)
Study
SES definition
SES categorization
Study Findings
Birkmeyer
201229
Summary score of SES
for each Michigan postal
ZIP code using data on
income, education, and
occupation from the 2000
US census.
Quintiles of SES score

Annual pre-tax household
income (self-reported).
Household income:
<$20,000;
$20,000-$29,999;
$30,000-$39,999;
$40,000-$49,999
$50,000-$69,999;
≥$70,000
Korda 201231
Area level disadvantage:
Based on the socioeconomic Indexes for
Areas Index of Relative
Socioeconomic
Disadvantage (IRSD).
Martin 201015
Wallace
201017
Worni 201237
Household income (selfreported).

Quintiles of Area-level
disadvantage
Quartiles of household
income
Median household income
in patient’s ZIP code of
residence.
Average annual household <$36,000;
income in the patient’s
$36,000-$44,999;
ZIP code of residence.
$45,000-$59,999;
≥$60,000
Average annual household ≤$34,999;
income in the patients ZIP $35,000-$44,999;
code of residence
≥$45,000




White patients in lower
SES quintiles were more
likely to undergo surgery
than white patients in
higher SES quintiles.
Racial minorities in lower
SES quintiles were less
likely to undergo surgery
than patient in the middle
to high SES quintiles.
Individuals more likely to
receive surgery if in the
highest income bracket or
quintile representing low
disadvantage when
compared to individuals in
the lowest income bracket
or quintile representing
high disadvantage
respectively.
20% of the individuals
receiving surgery were in
the lowest quartile of
income.
Patients with an average
household income
<$60,000 have lower odds
of receiving surgery
compared to those with a
household income
≥$60,000
Patients with an average
household income <
$45,000 have a lower odds
of receiving surgery
compared to those with a
household income
≥$45,000
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