A medical costs study of older patients with acute myocardial infarction and metabolic syndrome in hospital
Clinical Interventions in Aging
A medical costs study of older patients with acute myocardial infarction and metabolic syndrome in hospital
guan-qi Fan 2
Kai-li Fu 2
Cheng-wei Jin 2
Xiao-zhen Wang 1
Ming Zhong 2
Yun Zhang 2
Wei Zhang 2
Zhi-hao Wang 0 2
0 Department of geriatric Medicine, Qilu hospital of s handong University , Ji'nan, People's republic of China
1 s handong University of Traditional Chinese Medicine
2 Key l aboratory of Cardiovascular remodeling and Function research, Chinese Ministry of education and Chinese Ministry of Public health, Department of Cardiology, Qilu hospital of shandong University
PowerdbyTCPDF(ww.tcpdf.org) lu han 1 hui Wang 1 Background: Older patients with acute myocardial infarction (AMI) usually have a poor prognosis, but whether this poor prognosis leads to high hospital costs remains unclear. This study investigated the clinical outcomes of and costs incurred by older patients with AMI and metabolic syndrome (MS) in hospital. Methods and results: Patients with AMI seen at Qilu Hospital of Shandong University between January 2011 and May 2013 were separated into four groups: young non-MS patients (n=282), older non-MS patients (n=324), young MS patients (n=217), and older MS patients (n=174). We found that advanced age was significantly associated with worse clinical outcomes, and that the clinical outcomes in patients with AMI and MS are also worsened. At the same cost (RMB¥10,000), older patients with and without MS had a markedly increased number of cardiovascular incidences compared with younger patients without MS. In a comparison of the incremental cost-effectiveness ratio (ICER) of percutaneous coronary intervention, older patients without MS had a lower ICER for cardiovascular incidences and a higher ICER for cardiac event-free survival rate when compared with young patients without MS, but a lower ICER for cardiovascular incidences and a higher ICER for cardiac event-free survival rate when compared with older MS patients. Conclusion: Older AMI patients have poor clinical outcomes and their treatment is not costeffective; however, the results are worse in patients with AMI and MS. Percutaneous coronary intervention is a cost-effective therapy in older patients with AMI, but its cost-effectiveness decreases in patients with AMI and MS.
metabolic syndrome; aging; vascular; acute myocardial infarction; cost-
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open access to scientific and medical research
Introduction
As one of the largest populated countries in the world, the People’s Republic of China
is facing serious problems associated with aging. According to the Chinese National
Bureau of Statistics, the number of people aged 65 years and older increased to
12
7 million in 2012
, representing approximately 9.4% of the total population of the
People’s Republic of China. Moran et al reported that aging and population growth
will increase rates of cardiovascular disease by more than a half in the next 20 years
in the People’s Republic of China,1 which will be accompanied by a tremendous
economic burden.
Acute myocardial infarction (AMI) is one of the most deadly of the cardiovascular
diseases. Mortality following AMI increases exponentially with age, and is associated
with clinical features that vary according to age. Older patients are more likely to have
a “silent” or unrecognized AMI and to develop heart failure, atrial fibrillation, cardiac
rupture, and shock, all of which are associated with increased
mortality and a poor prognosis.2,3 However, whether the
medical costs of older AMI patients increases is not known.
The rapidly evolving management of patients with
AMI over recent decades has led to improved survival
rates.4–6 Although doctors seek more clinical effectiveness,
which is always costly, patients seek effective but inexpensive
18 management, leading to cost-effectiveness issues.
Percutanel-02 ous coronary intervention (PCI) is proven to be an effective
-J3u treatment for coronary artery disease. However, because of
n1o their clinical features and concerns about PCI, older AMI
702 patients are less likely to undergo this procedure.7 Studies
..64 show that PCI can decrease the risk of complications and
.795 improve the prognosis8–10 in older patients with AMI. In
y3b such situations, it is important to determine whether existing
/om therapies are cost-effective.
.css A recent study has shown that there is a high and rapidly
re growing incidence of metabolic syndrome (MS) in the elderly
.vdoepw l.syeon Chinese population.11 It is also known that MS is associated
w u with a poor prognosis in AMI patients.12–15 Thus, it would be
://sw lona worthwhile to determine if clinical outcomes are worse and
tthp rsep associated with increased hospital costs in elderly patients with
from roF both AMI and MS. To answer this question, we reviewed the
ed case files of patients admitted with AMI to Qilu Hospital of
ldoa Shandong University between January 20
11 and May 2013
and
onw analyzed their clinical outcomes and hospital costs.
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Methods
ethics statement
This research was approved by the ethics committee of Qilu
Hospital of Shandong University. Written informed consent
was given by the participants for their clinical records to be
used in this study. All data were anonymized and
deidentified prior to analysis.
Case file collection
We identified the case files of consecutive patients with a
discharge diagnosis of AMI at Qilu Hospital of Shandong
University between January 20
11 and May 2013
. In total,
1,150 patients were included. Information taken from these
case files included sex, height, weight, diagnosis on
admission, discharge diagnosis, duration of hospital stay, hospital
costs, history of smoking, past medical illness, family
medical history, laboratory examination, coronary arteriography,
cardiac ultrasound, complications, and drug treatment.
Definition of MS
Metabolic syndrome was defined by the Chinese Diabetes
Society criteria as the presence of three or all of the following
330
four characteristics: overweight and/or obesity (body mass
index 0.25 kg/m2); hyperglycemia (fasting plasma
glucose 6.1 mmol/L and postprandial glucose 7.8 mmol/L,
and/or diagnosed diabetes mellitus receiving treatment);
hypertension (systolic/diastolic blood pressure 140/90 mmHg,
and/or the diagnosed hypertension receiving treatment);
and lipid disorder (triglycerides 1.7 mmol/L and/or
high-density lipoprotein cholesterol 0.9 mmol/L for males
or 1.0 mmol/L for females).
grouping
We defined older patients as those aged older than 65 years.
The patients with AMI were separated to four
elderlyMS groups, ie, young non-MS patients (n=282), older non-MS
patients (n=324), young MS patients (n=217), and older MS
patients (n=174). One hundred and fifty-three cases could not
be categorized because of inadequate information.
statistical analysis
All analyses were conducted using Statistical Package for the
Social Sciences version 18.0 software (SPSS Inc., Chicago, IL,
USA) and P0.05 was considered to be statistically significant.
The results are expressed as the mean ± standard deviation or
as a proportion (%). For categorical variables, the χ2 test was
used. Analysis of variance was used to study the impact of
age and MS on duration of hospital stay and costs. Multiple
linear regressions using the stepwise method were performed
to examine predictors of hospital costs. Binary logistic
regressions using the forward conditional method were performed
to examine individual predictors of acute heart failure, atrial
arrhythmia, ventricular arrhythmia, and death in hospital.
Cost-effectiveness analysis
The formula used to calculate the cost-effectiveness ratio
(CER) is as follows:
CER = P
C
where P is the rate of complication and C is the mean total
cost. The formula used to calculate the incremental
costeffectiveness ratio (ICER) is as follows:
ICER = ∆P = P1 − P0
∆C C1 − C0
where P1 is the complication rate with PCI, C1 represents the
mean total costs of PCI, P0 is the complication rate without
PCI, and C0 is the mean total cost without PCI.
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Results
Baseline data
Table 1 shows the admission and treatment information for
the elderly-MS groups. Significant differences were found
between the different elderly-MS groups for all variables
except serum potassium and use of aspirin and
angiotensinconverting enzyme inhibitors.
hospital stay and costs
Table 2 shows the analysis of variance results for hospital
stay and costs in the elderly-MS groups. Hospital stay, total
costs, daily costs, medical treatment costs, laboratory
investigation costs, and tablet costs were significantly different
between the four groups. Analysis of variance showed that
patient age, but not MS, had a significant impact on duration
of hospital stay and costs. There was no age-MS interaction
in the models. Age is an influential factor, and we found that
older AMI patients had longer hospital stays, more laboratory
investigation costs, and tablet costs, but lower total costs,
daily costs, and medical treatment costs.
Major cardiovascular events
Table 3 shows the complication rates and cardiac event-free
survival rates in hospital for the elderly-MS groups. Increased
age was associated with a significantly higher rate of acute
heart failure as well as atrial and ventricular arrhythmia, and
a low cardiac event-free survival rate. However, the
relationship between increasing age and a higher risk of death did
not reach statistical significance. Similarly, there was no
statistically significant relationship when MS was considered.
However, in patients with both AMI and MS, increased age
led to more obvious differences when compared with older
non-MS patients. We also analyzed individual predictors of
acute heart failure, atrial arrhythmia, ventricular arrhythmia,
and death (Table S1).
Figure 1 shows the CER for different aspects of
cardiovascular events in the elderly-MS groups. At the same cost
of RMB¥10,000, young MS patients had a similar or slightly
higher rate of cardiovascular incidences than young non-MS
patients, and the latter had the lowest rate of cardiovascular
incidences; in contrast, older non-MS patients and older MS
patients both had a higher rate of cardiovascular incidences
compared with young non-MS patients. With regard to cardiac
event-free survival, older non-MS patients had the highest CER
at 18.8%, which decreased to 15.8% in older MS patients.
Cost-effectiveness of PCI
Table 4 shows that body mass index and PCI are major
predictors of total costs and daily costs. To examine whether
PCI is a cost-effective therapy, we calculated the ICER
for PCI.
Figure 2 shows the ICER for PCI in different aspects of
cardiovascular events in the elderly-MS groups. With an extra
RMB¥10,000 in young non-MS patients, rates of acute heart
failure and death decreased by 0.3% and 0.1%, respectively.
Atrial arrhythmia and ventricular arrhythmia both increased
by 0.6%, and cardiac event-free survival rate did not change.
With an extra RMB¥10,000 in older non-MS patients, rates
of acute heart failure decreased by 5.1%, atrial arrhythmia
by 1.6%, ventricular arrhythmia by 2.1%, and death by 0.7%,
and cardiac event-free survival increased by 3.9%. With an
extra RMB¥10,000 in young MS patients, acute heart failure
decreased by 2.9%, atrial arrhythmia by 0.7%, and death by
0.8%, while the ventricular arrhythmia rate did not change
and cardiac event-free survival increased by 4.0%. With an
extra RMB¥10,000 in older MS patients, acute heart failure
decreased by 2.6%, atrial arrhythmia by 0.7%, ventricular
arrhythmia by 0.9%, and death by 1.7%, while cardiac
eventfree survival increased by 2.8%.
The ICER value for older non-MS patients was smaller
than that for young non-MS patients when considering acute
heart failure, atrial arrhythmia, ventricular arrhythmia, and
death. However, the ICER for older non-MS patients was
higher than that for young non-MS patients when
considering cardiac event-free survival. These results mean adverse
cardiovascular events decrease more and cardiac event-free
survival increases more in older non-MS patients. Similarly,
when we compared the ICER for PCI between older non-MS
and older MS patients, we found that adverse cardiovascular
events, with the exception of death, decrease less and cardiac
event-free survival increases less in older MS patients.
Discussion
In this study, we found that older AMI patients had longer
hospital stays and more laboratory investigations,
examination costs, and tablet costs, but lower total costs, daily
costs, and medical treatment costs. For the same total costs,
older AMI patients had a higher complication rate, which
is more obvious when AMI is combined with MS. PCI is
cost-effective in older patients with AMI, but this effect is
partly offset in patients with both AMI and MS.
We observed that AMI patients aged younger than
65 years were more likely to be males. In addition, younger
patients had more of a smoking history and family history
of hypertension, diabetes, coronary heart disease, and stroke
compared with older patients. Increased triglycerides and
decreased high-density lipoprotein, as main components
of MS, were apparent in young AMI patients. All of these
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P-value
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suggest male sex, smoking history, family history of
cardiovascular disease, and dyslipidemia are risk factors in young
patients with AMI.16–18
Our results show that older patients with AMI had longer
hospital stays but lower total costs. At baseline, older patients
with AMI had high levels of blood urea nitrogen, creatinine,
cystatin C, uric acid, and urinary protein, indicating poor renal
function which may account for their longer hospital stays.
There are reports in the literature showing that the duration
of hospital stay in patients with AMI is associated with PCI,
complications, and sex.19,20 Our results show that PCI is the main
factor influencing hospital costs in patients with AMI, which is
in accordance with other reports.21,22 The lower PCI rate in older
patients with AMI may account for their lower total costs.
The impact of MS on hospital stay and costs in patients
with AMI has not been well reported. Our results show that
MS did not result in longer hospital stays and lower total
costs in patients with AMI. The reason could be that the
impact of each MS component on AMI is different, which
may counterbalance the total effect.
We found that older AMI patients were more likely to
experience cardiovascular complications and less likely to
survive free of cardiac events, which is in agreement with
previous research.23 We evaluate the cost-effectiveness of
management in AMI patients at Qilu Hospital of Shandong
University using a CER comparison. We found that older
non-MS patients had a higher CER in terms of complications
and cardiac event-free survival, it was difficult to determine
whether the management in older non-MS patients is
costeffective. We presume that management of older non-MS
patients is cost-effective, but this cost-effectiveness decreases
when complications of AMI occur. Older MS patients had a
high CER in terms of complications and a low CER in terms
of cardiac event-free survival, suggesting that management
in older MS patients is not cost-effective. In other words,
MS decreases the cost-effectiveness of management in older
patients with AMI.
Our results show that PCI is cost-effective in older
patients and those with MS, and the cost-effectiveness
decreases when the two factors are combined, while the
cost-effectiveness of PCI compared with that of drug therapy
is equal in young non-MS patients with AMI. These results
help to inform patients about the cost-effectiveness of PCI
in their particular circumstances. There has been a recent
report showing that female AMI patients aged younger than
40 years have a higher long-term mortality rate than their
male counterparts after PCI,24 suggesting that the
effectiveness of PCI in young AMI patients is sex-related. However,
how sex influences the cost-effectiveness of PCI in AMI
patients needs further investigation.
Our study has several limitations. Firstly, it was a
retrospective observational study, so we could not determine the
Ventricular arrhythmia
n (%)
16 (5.7)
28 (8.6)
9 (4.1)
24 (13.8)*†
0.003
Death
n (%)
3 (1.1)
7 (2.2)
2 (0.9)
7 (4.0)
0.115
Cardiac event-free
survival n (%)
258 (91.5)
244 (75.3)*†
190 (87.6)
122 (70.1)*†
0.001
A
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2.5%
1.1%
MS
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io 0.0%
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MS
Acknowledgments
This work was supported by research grants from the
National Basic Research Program of China (973
Program, 2013CB530700), the National Natural Science
Foundation of China (81070192, 81070141, 81100605,
81270352, and 81270287), the Natural Science
Foundation of Shandong Province (BS2013YY017), the
Independent Innovation Foundation of Shandong University
(2012JC034), and the Cardiovascular Exploration Research
Foundation of the Chinese Medical Doctor Association
(DFCMDA201320).
Disclosure
The authors report no competing interests in this work.
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submit your manuscript | www.dovepress.com
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Supplementary material
in elderly AMI patients
Ventricular arrhythmia
glucose
0.187
1.568
−1.910
−1.833
Abbreviations: AMI, acute myocardial infarction; NEFA, nonesterified fatty acids; PLIP, phospholipids; HDL, high-density lipoprotein; ARB, adrenergic receptor blocker;
CI, confidence interval; OR, odds ratio.
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−1.274 −0.021 1 . 630 − 0 .967 P-value