Moderate and Severe Obesity
Have Large Differences
in Health Care Costs
Tatiana Andreyeva, RAND Graduate School
Roland Sturm, RAND
Jeanne S. Ringel, RAND
Why look at health care costs across
obesity groups?
• Obesity-related health problems are particularly
common among severely obese individuals
• One would expect commensurate differences in
health care costs across obesity groups, yet few
data are available
• The prevalence of severe obesity is increasing at
a much faster rate than the spread of obesity
Obesity and Health Status
45
% reporting fair or poor health
40
35
30
25
20
15
10
5
0
Normal, 18.5<BMI<25
Obese, 30<BMI<35
Overweight,
25<BMI<30
Males 50-69
Severely obese,
BMI>35
Females 50-69
Source: Sturm et al, Health Affairs, March 2004
Obesity and Disability
% with any ADL limitation
20
18
16
14
12
10
8
6
4
2
0
Normal, 18.5<BMI<25
Overweight,
25<BMI<30
Obese, 30<BMI<35
Males 50-69
Severely obese,
BMI>35
Females 50-69
Source: Sturm et al, Health Affairs, March 2004
Severe obesity is increasing at a much
faster rate than the spread of obesity
500
BMI>=30
BMI>=35
400
BMI>=40
BMI>=45
300
BMI>=50
200
100
19
86
19
87
19
88
19
89
19
90
19
91
19
92
19
93
19
94
19
95
19
96
19
97
19
98
19
99
20
00
Percentage Increase (1986=100)
600
Source: Sturm, Arch Internal Med, Oct 2003
Our Approach
• Estimate the association between obesity
and health care utilization and
expenditures across varying degrees of
obesity
– Data from Health and Retirement Study,
1996-2000
Methodology
• Main dependent variables:
– Health care utilization
• outpatient visits, hospitalization, inpatient days
– Total health care expenditures
• Main explanatory variable: BMI weight class
– Normal weight (18.5-25), Overweight (25-30),
Moderate obesity (30-35), Severe obesity (35-40), and
Extreme obesity (40+)
• Analyze data cross-sectionally
Model Estimation Results
• Average predicted health care utilization
and costs
• Adjusted for sociodemographic
characteristics and behavioral risk factors
• By weight class
Obesity and Health Care Costs
9000
Annual total health care costs in 2002 $s
8000
7000
6000
5000
4000
3000
2000
1000
0
Obese, 30<BMI<35
Severely obese, 35<BMI<40
Males 54-69
Extremely obese, BMI 40+
Females 54-69
Obesity and Health Care Utilization
18
Number of outpatient visits
16
14
12
10
8
6
4
2
0
Obese, 30<BMI<35
Severely obese, 35<BMI<40
Males 54-69
Extremely obese, BMI 40+
Females 54-69
Obesity and Health Care Utilization
Number of inpatient days
3.5
3
2.5
2
1.5
1
0.5
0
Obese, 30<BMI<35
Severely obese, 35<BMI<40
Males 54-69
Extremely obese, BMI 40+
Females 54-69
Limitations
• Self-reported height and weight
underestimate BMI
• Limited age range of HRS data
• Excluded institutionalized population
• Cross-sectional estimates and cannot be
interpreted as causal effects
Discussion
• Widely cited average effects of obesity on health
care costs (36-37%) obscure major differences
across obesity groups
– BMI of 35-40 is associated with twice the increase in
medical expenditures above normal weight (50%
increase) than BMI of 30-35 (25% increase)
– BMI of 40+ doubles costs (100% above normal weight)
• Average estimates will underpredict future health
care costs because severe obesity grows at a
much faster rate than obesity in general
Conclusion
An increasing burden of obesity on the health
care system grows disproportionally for the
most obese segment of the US population
As the prevalence of severe obesity increases
at a much faster rate than that of obesity,
average estimates of obesity effects obscure
real consequences for individuals, hospitals
and health plans.
Back up
Model Estimation
• Log-linear model for health care
expenditure data
– Better fit the data than alternative models in
cross-validation tests
– Homogenous smearing transformation
• Linear model for continuous utilization
outcomes (number of doctor visits and
hospital days) and a probit model for any
inpatient stay
• Analyze data separately by gender
Obesity and Health Care Costs
9000
Annual total health care costs in 2002 $s
8000
7000
6000
5000
4000
3000
2000
1000
0
Obese, 30<BMI<35
Severely obese,
35<BMI<40
Extremely obese,
BMI>=40
Individuals ages 54-69
Obesity, BMI>=30
Obesity and Health Care Utilization
Number of outpatient visits
18
16
14
12
10
8
6
4
2
0
Obese, 30<BMI<35
Severely obese,
35<BMI<40
Extremely obese,
BMI>=40
Individuals ages 54-69
Obesity, BMI>=30
Obesity and Health Care Utilization
Number of inpatient days
3.5
3
2.5
2
1.5
1
0.5
0
Obese, 30<BMI<35
Severely obese,
35<BMI<40
Extremely obese,
BMI>=40
Individuals ages 54-69
Obesity, BMI>=30
Obesity and Health Care Utilization
% with any inpatient stay
35
30
25
20
15
10
5
0
Obese, 30<BMI<35
Severely obese, 35<BMI<40
Males 54-69
Extremely obese, BMI 40+
Females 54-69