Comparative cardiovascular effects of thiazolidinediones:systematic review and meta-analysis of observationalstudies
Yoon Kong Loke, senior lecturer in clinical pharmacology,1 Chun Shing Kwok, medical student,1 Sonal Singh,assistant professor of medicine2
because of concerns about adverse cardiovascular
Objective To determine the comparative effects of the
events.2 Rosiglitazone and pioglitazone are the available
thiazolidinediones (rosiglitazone and pioglitazone) on
thiazolidinediones in North America, but meta-analyses
myocardial infarction, congestive heart failure, and
of randomised controlled trials have suggested an
mortality in patients with type 2 diabetes.
increased risk of ischaemic cardiovascular events with
Design Systematic review and meta-analysis of
rosiglitazone.34 In contrast, meta-analysis of trials of pio-
glitazone indicates the possibility of an ischaemic cardio-
Data sources Searches of Medline and Embase in
vascular benefit.5 Robust evidence also shows that both
drugs increase the risk of congestive heart failure and
Study selection Observational studies that directly
fractures, but whether any meaningful difference exists
compared the risk of cardiovascular outcomes for
in the magnitude of risk between the two thiazolidine-
rosiglitazone and pioglitazone among patients with type
diones is not known.67 The European Medicines
Agency has recommended the suspension of marketing
Data extraction Random effects meta-analysis (inverse
authorisation for rosiglitazone, whereas the US Food
variance method) was used to calculate the odds ratios
and Drug Administration has allowed the continued
for cardiovascular outcomes with thiazolidinedione use.
marketing of rosiglitazone with additional restrictions.8
The I2 statistic was used to assess statistical
No long term trials with cardiovascular outcomes
have directly compared these two drugs. Clinical trials
Results Cardiovascular outcomes from 16 observational
have strict selection criteria that may exclude partici-
studies (4 case-control studies and 12 retrospective
pants at high risk of adverse events, and adverse
cohort studies), including 810 000 thiazolidinedione
cardiovascular outcomes can be rare in such trials.9
users, were evaluated after a detailed review of 189
On the other hand, population based observational
citations. Compared with pioglitazone, use of
studies resemble clinical practice, where patients may
rosiglitazone was associated with a statistically
have risk factors for cardiovascular disease or comor-
significant increase in the odds of myocardial infarction
bidities. Therefore, consideration of the evidence from
(n=15 studies; odds ratio 1.16, 95% confidence interval
carefully conducted observational studies is essential
1.07 to 1.24; P<0.001; I2=46%), congestive heart failure
to determine if any difference in cardiovascular events
(n=8; 1.22, 1.14 to 1.31; P<0.001; I2=37%), and death
or mortality exists between the two drugs.
(n=8; 1.14, 1.09 to 1.20; P<0.001; I2=0%). Numbers
Our objective was to systematically determine the
needed to treat to harm (NNH), depending on the
comparative effects of rosiglitazone and pioglitazone
population at risk, suggest 170 excess myocardial
on cardiovascular outcomes (myocardial infarction
infarctions, 649 excess cases of heart failure, and 431
and congestive heart failure) and mortality from obser-
excess deaths for every 100 000 patients who receive
vational studies in patients with type 2 diabetes. We
rosiglitazone rather than pioglitazone.
aimed specifically to calculate the pooled odds ratios
Conclusion Among patients with type 2 diabetes, use of
for adverse cardiovascular events with rosiglitazone
rosiglitazone is associated with significantly higher odds
compared with pioglitazone—that is, the relative like-
of congestive heart failure, myocardial infarction, and
lihood of cardiovascular harm if rosiglitazone was used
death relative to pioglitazone in real world settings.
Troglitazone, the first thiazolidinedione, was withdrawn
from the market because of liver toxicity.1 Muraglitazar,
We selected controlled observational (non-randomised)
a dual peroxisome proliferator activated receptor
studies that reported on cardiac outcomes in patients
(PPAR) agonist, failed to achieve regulatory approval
receiving rosiglitazone compared with pioglitazone.
Any uncertainties or discrepancies between the two
reviewers were resolved through consensus after re-
checking of the source data and consultation with thethird reviewer. We also contacted authors if any areasof uncertainty needed clarification.
Titles and abstracts screened for studies
Where different timings and durations of thiazolidi-
that might be potentially relevant (n=189)
nedione use were reported in the study participants, we
Review articles, trial reports, or clearly not observational
pre-specified that data would be preferentially extra-
studies of cardiovascular events with rosiglitazone v
cted from the participants with current or most recent
pioglitazone in patients with type 2 diabetes (n=153)
use, until cessation of treatment. We also aimed to
Potentially relevant studies for full checking (n=36)
extract risk estimates pertaining to overall use in theentire cohort rather than in any specific subgroups.
Excluded (n=20): Did not report on direct comparison of rosiglitazone v pioglitazone (n=15)
Earlier study that used same database population as a later study (n=1)
In accordance with the recommendations of the
Cochrane Adverse Effects Methods Group, wechecked the methods of selection of participants
Observational studies with direct comparison of cardiac
outcomes or mortality for rosiglitazone v pioglitazone (n=16)
(including baseline characteristics and adjustment forconfounders), nature of follow-up, ascertainment ofdrug use, and definition and monitoring of adverse
Fig 1 | Flow diagram of process of selection of articles for
outcomes.10 To counter selective reporting bias, we
contacted authors when relevant cardiovascular out-comes were potentially measured but were not
We included studies of a cohort or case-control design
reported or were stated to be non-significant. We
that enrolled participants with type 2 diabetes mellitus.
used a funnel plot to assess publication bias.
The primary outcome of interest was myocardial infarc-tion. Secondary outcome measures were congestive
heart failure and overall mortality. Eligible studies had
We used RevMan 5.0.25 (Nordic Cochrane Centre) to
to present one of the following: odds ratio, relative risk,
do random effects meta-analysis using the inverse var-
hazard ratio, or sufficient raw data to enable calculationof the odds ratio where not otherwise reported.
iance method for pooled odds ratios. We used the fixedeffects model for sensitivity analysis. We assumed simi-
larity between the odds ratio and other relative mea-sures such as relative risk, rate ratios, or hazard ratios
We searched Medline and Embase by using Ovid SP
because cardiovascular events and deaths were rare
(from inception to the end of September 2010), with
the search terms (pioglitazone or rosiglitazone or thia-zolidinedione$).mp and (myocardial-infarction or
Where possible, we aimed to pool adjusted odds
cardiovascular or cardiac or heart).mp and (cohort or
ratios from the primary studies; otherwise, we used
case-control or observational or retrospective).mp. We
raw outcome data to yield unadjusted odds ratios. In
did not use any language restrictions, but we limited
view of the potential diversity of study designs, we
the search to human studies. Additionally, we signed
grouped the studies for the analysis according to stu-
up with PubMed to receive automated electronic noti-
dies for which only the unadjusted odds ratios were
fication of any new articles containing the above search
available, with no correction for baseline differences
terms. To identify unpublished studies, we reviewed
or confounding, and those for which we were able to
the regulatory authorities websites (US Food and
extract odds ratios adjusted for potential confounders.
Drug Administration and European Medicines
For consistency in direction of risk comparisons, we
Agency), as well as the study registers of the drug man-
used the odds ratio to assess the magnitude of risk for
ufacturers GlaxoSmithKline and Takeda. We checked
rosiglitazone use compared with that for pioglitazone
the bibliographies of included studies and recent
use. For studies that reported the odds ratio for piogli-
review articles for additional relevant articles.
tazone compared with rosiglitazone, we used the reci-procal of the point estimate and the bounds of the
Two reviewers (CSK and YKL or SS) checked all titles
We estimated the number needed to treat to harm
and abstracts for studies that could potentially meet the
per year (NNH) (and 95% confidence interval) by
inclusion criteria. We retrieved full reports of these
applying the pooled odds ratio from the meta-analysis
potentially eligible studies for detailed assessment by
to the annual rate of the event in different
two reviewers (CSK and YKL), who then indepen-
populations.12 The NNH is the number of patients
dently extracted information on study design, drug
with type 2 diabetes who need to be treated with rosi-
use, study location, characteristics of participants, and
glitazone rather than pioglitazone for one additional
relevant outcomes on to a preformatted spreadsheet.
Table 1 | Design and characteristics of included studies
Retrospective cohort study (TRIAD); 564 rosiglitazone;
Type 2 diabetes, age >18 years, not pregnant,
community patients; USA, 1999 to 334 pioglitazone
community dwelling, English or Spanish speaking, and thiazolidinediones were
enrolled in health plan for ≥18 months; excluded
if >1 type of thiazolidinedione prescription
Aged >18 years with diabetes or HbA1C >6% and
≥1 oral diabetes drug; excluded if used metformin
or thiazolidinedione for polycystic ovaries
Previous metformin users; excluded if received other
oral antidiabetic drug or insulin within 365 days before MI OR 1.00 (0.67 to 1.49)
Pharmanet database, BC, Canada, 462 rosiglitazone and
starting metformin or emigrated/died before May 2003
≥6 month enrolment and >65 years who started
rosiglitazone or pioglitazone; excluded if residing
in a hospital, long term care home, or hospice
Newly diagnosed type 2 diabetes with ≥3 prescriptions Unadjusted data for entire
of oral diabetes drug; excluded if had type 1 diabetes or cohort: MI ros 1984/49 624,
pio 356/12 010; HF ros 664/49 624, pio 115/12 010
Residents of Ontario, >66 years of age starting
thiazolidinedione treatment; excluded if using insulin
Patients with type 2 diabetes and ≥1 prescription claim MI OR 1.12 (0.99 to 1.26)
for antidiabetic drug, with ≥1 year enrolment in
healthcare plan; those with heart failure or ischaemic
heart disease were included, but those with MI were
Aged ≥66 years with diabetes and dispensed ≥1 oral
hypoglycaemic agent in study period; excluded if
received insulin in year preceding cohort entry
134/920; HF ros 426/1907,pio 160/929; mortality ros434/1716 pio 165/715
Patients with two records of diabetes between 2002
Type 2 diabetes with prescription for rosiglitazone,
pioglitazone, metformin, or sulfonylurea, age >18 years mortality 1.23 (0.79 to 1.92)
with no history of dialysis, CAD, or HF; excluded if
prescribed insulin or multiple oral agents
Patients aged 18-84 years with a filled prescription for MI OR 1.26 (0.79 to 2.00)
database of Prescription Solutions 6653 controls; drug use:
antidiabetic drug or exenatide during study period;
excluded if had type 1 diabetes, cancer, renal or liver
failure, organ transplantation, or HIV infection
Patients aged 35-90 years with episode of care
between 1990 and 2005 associated with clinical or
referred event for diabetes; excluded if date of death
Users of oral hypoglycaemic agents who had
≥6 months’ membership in health plan, age >18 years; MI 1.21 (0.95 to 1.54)
excluded if in health plans for which data had been
Aged >18 years with new rosiglitazone or pioglitazone
claim; excluded if not in health plan >365 days before
index date or had pre-index pharmacy claim of insulin; 1.02 (0.86 to 1.21)
those with previous cardiovascular events were notexcluded
Age >65 years with new prescription for
thiazolidinedione; excluded if used troglitazone or
Ziyadeh 200929 Retrospective cohort study; i3
Age >18 years, starting rosiglitazone or pioglitazone,
followed by >6 months of health plan membership;
of patients were male across 15 studies. Table 1 shows
We used the I2 statistic to assess statistical heterogene-
the main characteristics of the studies and participants;
ity. I2 values of 30-60% represented a moderate level of
table 2 shows the outcomes, interventions, and quality
Figure 1 shows the process of selection of studies. We
The included studies were broadly similar in terms of
retrieved 16 observational studies involving 810 000
ascertainment of drug use and cardiovascular out-
thiazolidinedione users (429 000 patients taking rosi-
comes (table 2); they relied mainly on computerised
glitazone and 381 000 taking pioglitazone), after a
diagnostic codes, pharmacy claims databases, and ret-
detailed review of 189 citations.14-29 Fifteen studies
rospective chart reviews. Few researchers made
reported on the outcome of myocardial infarction,
attempts to verify drug history directly with the
eight studies reported on the outcome of congestive
patients or to check the validity of the prescriptions
heart failure, and eight studies reported on mortality.
data source; only one study was deemed to have spe-
We found 12 retrospective cohort studies and four
cific validation of drug use.14 Most studies reported the
case-control studies. The mean or median follow-up
accuracy of outcome ascertainment on the basis of his-
time ranged from 105 days to 7.1 years. Four studies
torical validation studies; only two studies specifically
reported duration of thiazolidinedione use, with a
cross checked or validated outcomes for this
range of 215 to 450 days. The mean age of participants
analysis.15 23 Both of these studies showed a limited
ranged from 54 to 76 years across studies, but most
study participants were generally aged above
None of the studies provided details about the sever-
60 years; only two studies reported the average age of
ity and consequences of the cardiac adverse events.
their participants as under 60 years. An average of 55%
Almost all the studies used a wide variety of variablesto adjust for potential confounders. Two cohort studies
checked specifically for similarities between the rosigli-
tazone and pioglitazone populations and did not find
evaluated.17 19 We were able to use adjusted risk esti-
mates for most studies, except for two studies for
which we calculated odds ratios from the raw
Compared with pioglitazone, use of rosiglitazone was
associated with a significantly increased odds of myo-
cardial infarction from 15 studies (pooled odds ratio
1.16, 95% confidence interval 1.07 to 1.24; P<0.001)
(fig 2). We found a moderate level of heterogeneity
(I2=46%) for the pooled results for myocardial infarc-
tion, which stemmed from combining the unadjusted
and adjusted studies together for the overall estimate.
χ2=14.25, df=12, P=0.28, I2=16%Test for overall effect: z=3.19, P=0.001
Heart failureBased on the pooled results of eight studies, the odds of
congestive heart failure were statistically significantly
higher for rosiglitazone than for pioglitazone (odds
ratio 1.22, 1.14 to 1.31; P<0.001), with moderate statis-
tical heterogeneity (I2=37%) (fig 3).
Test for heterogeneity: τ2=0.00, χ2=0.34, df=1, P=0.56, I2=0%
Test for overall effect: z=5.68, P<0.001
The odds of death were statistically significantly higherfor rosiglitazone than for pioglitazone when we pooled
eight studies, with an odds ratio of 1.14 (1.09 to 1.20;
P<0.001) (fig 4). We found no evidence of statistical
heterogeneity for this outcome (I2=0%).
Test for overall effect: z=3.87, P<0.001
In a low risk population (age 45-64 years) with type 2
Fig 2 | Meta-analysis of odds ratio for myocardial infarction with rosiglitazone versus
diabetes but no previous history of myocardial infarc-
tion, the underlying incidence of myocardial infarction
we did a post hoc analysis by excluding the single study
that had a substantial proportion of patients recruited
after May 2007.17 This did not appreciably change the
direction and magnitude of the estimates for myo-
cardial infarction (odds ratio 1.17, 1.08 to 1.27), heart
failure (1.21, 1.10 to 1.33), and overall mortality (1.13,
1.04 to 1.24). Further exclusion of another study
(recruitment dates 2002 to 2008) did not appreciably
change the odds ratios for myocardial infarction (1.19,
1.09 to 1.29), heart failure (1.18, 1.06 to 1.33), and over-
χ2=7.88, df=5, P=0.16, I2=37%Test for overall effect: z=4.58, P<0.001
The funnel plot showed that risk estimates stemmed
mostly from large, precise studies that seemed to be
fairly well distributed, with no definite evidence of
Test for heterogeneity: τ2=0.00, χ2=0.01, df=1, P=0.91, I2=0%
Test for overall effect: z=4.58, P<0.001
Our results suggest a modest but statistically significantincrease in the odds of myocardial infarction (approxi-
mately 16%), congestive heart failure (approximately
23%), and mortality (approximately 14%) with use of
rosiglitazone compared with those for pioglitazone use
Test for overall effect: z=5.64, P<0.001
in real world studies among patients with type 2 diabetes.
The consistency in the magnitude of increased risk for
the different cardiac outcomes, as well as mortality, indi-
cates that this is unlikely to be a chance finding. Other
Fig 3 | Meta-analysis of odds ratio for heart failure with rosiglitazone versus pioglitazone
strengths of our analysis include the large number ofthiazolidinedione users (around 810 000) and the
was 1.08% per year.30 Use of rosiglitazone here would
absence of substantial statistical heterogeneity, which
result in an annual NNH of 587 (95% confidence inter-
suggests that the risk is maintained across most popula-
val 392 to 1339). This can be equated to 170 excess
tions and is unaffected by geographical variations.
myocardial infarctions for every 100 000 patientswho received rosiglitazone rather than pioglitazone.
In a US cohort of patients with type 2 diabetes, the
Our synthesis of evidence from observational studies
baseline incidence of heart failure was found to be
extends the findings of a cardiovascular hazard with
3.08% per year.31 Use of rosiglitazone here would
rosiglitazone from meta-analysis of clinical trials to
result in an annual NNH of 154 (110 to 241). This
real world settings and suggests the possibility of a
can be equated to 649 excess cases of heart failure for
cardiovascular difference between the two drugs.3-5Adjusted indirect comparisons of the risk estimates
every 100 000 patients who received rosiglitazone
from meta-analysis of myocardial infarction and heart
failure in randomised controlled trials shows that rosi-
In a large French registry study of patients with type
glitazone is associated with an increased relative risk of
2 diabetes and atherosclerosis, the underlying mortal-
1.58 (95% confidence interval 1.14 to 2.20) for myo-
ity rate was found to be 3.15% per year.32 Use of rosi-
cardial infarction and 1.48 (1.01 to 2.18) for heart fail-
glitazone here would result in an annual NNH of 232
ure, compared with pioglitazone.3-534 The direction of
(163 to 360). This can be equated to 431 excess deaths
effect for both outcomes is consistent with our analysis,
for every 100 000 patients who received rosiglitazone
whereas the relatively lower point estimates seen in our
analysis may reflect the generally more conservativenature of estimates of harm that has been noted with
observational studies.35 Participants in trials may differ
Meta-analysis using the fixed effects model yielded
from those in observational studies, because most of
estimates that were similar in direction and magnitude
the observational studies recruited a wider, more gen-
to those from the random effects model for myocardial
eralisable range of patients by not enforcing rigid inclu-
infarction (odds ratio 1.15, 1.10 to 1.21), heart failure
sion and exclusion criteria relating to comorbid
(1.23, 1.17 to 1.29), and overall mortality (1.14, 1.09 to
conditions. Of the 16 included studies, two excluded
patients with existing cardiac conditions (so that they
In view of potential patient selection bias arising
could study incident disease)20 23 and only one
after publication of a meta-analysis in May 2007 that
excluded patients who had comorbidities such as
showed increased myocardial risk with rosiglitazone,33
Table 2 | Drug use, study outcomes, and potential sources of bias
MI and all cause mortality ascertained by ICD codes on Age, sex, race, income, history of diabetic nephropathy, history of
health plan administrative data and national death
cardiovascular disease, insulin use, and health plan
MI ascertainment based on ICD codes and randomly
Age, sex, cardiovascular disease, antihypertensive and lipid lowering
selected case notes/discharge summaries with
sensitivity of 94% and specificity of 74% for outcomes
MI ascertainment based on ICD codes of hospital
Duration of diabetes; congestive heart failure; angiography;
admission records (primary reason for admission)
revascularisation; ischaemic stroke; TIA; previous MI; angina; renal
collected by Ministry of Health; controls were patients
disease; Romano comorbidity score; use of cardiac drugs, clopidogrel, and
starting metformin matched on age, sex, number of
insulin; and past use of metformin, glitazones, and sulfonylureas
family members, health plan enrolment, and income
MI and heart failure based on ICD discharge codes with Sex, age, race, low income, extended care, Charlson score, cardiovascular
positive predictive values of >90%; mortality
disease and drugs, lipid lowering drugs, and comorbidities
ascertained by linkage to social security master
beneficiary record database, which captures 95% ofdeaths for older people
MI and heart failure ascertainment based on ICD codes Data used in unadjusted form in meta-analysis
ascertained with prescription claims for inpatient claims
All cause mortality, MI, and heart failure obtained from Age, sex, residence, socioeconomic status, year of entry, duration of
national ambulatory care reporting system database,
diabetes, acute MI, angina, congestive heart failure, coronary angiography,
Canadian Institute for Health information discharge
CABG, PCI, Charlson index, history of renal disease, and previous drugs
database, and Ontario health insurance database
(antihypertensives, aspirin, NSAIDs, nitroglycerin preparations, statins,
Cases had ICD code for hospital admission for MI
Age; use of ACE inhibitors, β blockers, diuretic, or nitrate; hyperlipidaemia;
occurring ≥3 months after diagnosis of diabetes;
controls were randomly selected from eligible matchedpatients within cohort who did not have ICD code for MI
MI, heart failure, and mortality data from registered
Data used in unadjusted form in meta-analysis
persons databases and hospital discharge summaryabstract database
MI and coronary artery disease (MI, unstable angina,
Age; sex; BMI; HbA1C; smoking; chronic kidney disease; eGFR; mean
cardiac death, coronary artery reperfusion procedure)
arterial blood pressure; and history of MI, unstable angina, or cardiac
based on computerised read codes in general practice proceduredatabase; approximately 3% lost to follow-up
Pantalone 200923 Drug use at baseline based on
Heart failure and mortality data from ICD codes and
Age, sex, race, eGFR, albumin/urine creatinine ratio, HbA1C, BMI, systolic
electronic health records database; small proportion of blood pressure, diastolic blood pressure, HDL, LDL, triglycerides, smoking
mortality records from social security death index had
status, cardiovascular drugs, new diabetes, and median household
errors on cross checking and were corrected for
MI cases based on ICD codes for hospital admission;
Age, cardiovascular risk score, non-cardiovascular acute hospital
controls were matched on various parameters with
admission, COPD, and use of oestrogen therapy
specific group constructed for analysis of rosiglitazonev pioglitazone
MI, heart failure, and mortality; unclear outcome
Age, sex, duration of diabetes, complications of diabetes, cardiovascular
and peripheral artery disease, co-prescribed drugs, BMI, cholesterol
concentration, systolic blood pressure, HbA1C, creatinine concentration,albumin concentration, and smoking status
MI based on hospital discharge diagnosis and ICD code Propensity score used to adjust according to demographics, calendar time,
use of antidiabetic drugs, history of MI, coronary revascularisation, angina,
ACS, congestive heart failure, hyperlipidaemia, hypertension, obesity,
MI, heart failure, and mortality from medical claims, ICD Propensity score used to adjust for age, sex, health plan, Deyo-Charlson
codes, and national death index plus database; mean comorbidity index score, cardiovascular and peripheral vascular disease,
cardiovascular and antidiabetic drugs, obesity, smoking status, anddiabetic complications
Unclear how mortality was ascertained; MI and heart
Cardiovascular disease, cerebrovascular disease, congestive heart failure,
codes for prescription claims; mean failure data from Medicare claims
previous insulin treatment, and nitrate use
MI data from hospital discharge diagnosis and ICD
Propensity score matching used with adjusted analysis for variety of
code as primary event; “sudden death” events
demographic and cardiovascular risk factors
captured through ambulance codes for resuscitation/
ACS=acute coronary syndrome; BMI=body mass index; CABG=coronary artery bypass graft; CAD=coronary artery disease; COPD=chronic obstructive pulmonary disease; eGFR=estimatedglomerular filtration rate; HbA1c=glycated haemoglobin; HDL=high density lipoprotein cholesterol; ICD=international classification of diseases; LDL=low density lipoprotein cholesterol;MI=myocardial infarction; NSAID=non-steroidal anti-inflammatory drug; PCI= percutaneous coronary intervention; TIA=transient ischaemic attack.
retention, may explain its greater risk of congestive
Our findings have important implications. Rosiglita-
zone is still available on a restricted basis in the United
States and Canada.8 41 However, for patients who need
thiazolidinedione treatment, continued use of rosiglita-
zone may lead to excess heart attacks, heart failure, and
mortality, compared with pioglitazone. The size of the
effect on public health may be considerable, given the
data from June 2009 showing that about 3.8 million
Test for overall effect: z=5.05, P<0.001
annually in the United States.42 However, other
adverse effects are associated with both the thiazolidi-
nediones, such as the doubling of risk of fracture in
women.7 Concerns also exist about a modest increase
in the risk of bladder cancer with pioglitazone after
long term use in an observational study and a higherpercentage of bladder cancers with pioglitazone rela-
tive to comparator arms in long term randomised con-
trolled trials.43 Further studies are needed to investigate
these other adverse events, as clinicians need to bal-
Test for overall effect: z=5.18, P<0.001
ance these risks and benefits against those of emerging
alternative agents such as incretin mimetics that may or
may not be safer than thiazolidinediones.
Fig 4 | Meta-analysis of odds ratio for overall mortality with rosiglitazone versus pioglitazone
Our analysis has some limitations, relating mainly to
As both drugs are known to cause heart failure, the
the quality of the primary studies. Misclassification of
increased risk of congestive heart failure associated with
outcomes and drug use may occur in observational stu-
rosiglitazone compared with pioglitazone represents its
dies that rely on healthcare databases and discharge
differentialcardiovasculartoxicity.Twointerpretations
codes. However, any potential misclassification of
for their differential effects on myocardial infarction are
drug use and outcomes would affect both thiazolidine-
possible. One possibility is that these findings represent
diones equally. Non-randomised data are susceptible
an ischaemic cardiovascular benefit with pioglitazone.
to selection bias and residual confounding. However,
However, conclusive evidence on ischaemic cardio-
investigators of the two largest cohort studies found
vascular benefit with pioglitazone is lacking; a meta-
little difference in the baseline demographics and
analysis of trials yielded a relative risk of 0.81 (0.64 to
cardiovascular risk of patients who used pioglitazone
1.02) formyocardialinfarction.Theotherpossibilityis a
and rosiglitazone.17 19 Both drugs are from the same
greater ischaemic cardiovascular hazard with rosiglita-
class and were licensed for similar indications. Until
zone, consistent with evidence from clinical trials.3 4
May 2007, no reasons existed why any specific groupof patients would have been systematically channelled
towards one thiazolidinedione or the other. Our risk
The precise biological mechanisms responsible for
estimates did not change despite exclusion of the two
these differences in cardiovascular risk and mortalityare uncertain. Significant differences have been found
between the thiazolidinediones in lipid metabolism;rosiglitazone causes greater elevations of triglycerides
and low density lipoprotein cholesterol than does
pioglitazone.36 Pioglitazone had a significantly more
favourable effect on triglycerides, high density lipopro-tein cholesterol, low density lipoprotein particle con-
centration, and low density lipoprotein particle size
than did rosiglitazone. Whereas pioglitazone hasshown some potential benefit in preventing progres-
sion of atherosclerosis,37 rosiglitazone failed to show
any significant effect in preventing atherosclerosis in
a recent study.38 The more powerful renal PPARγ ago-
Fig 5 | Funnel plot based on odds ratio for myocardial
nistic effect of rosiglitazone, leading to more fluid
Lincoff AM, Wolski K, Nicholls SJ, Nissen SE. Pioglitazone and risk of
cardiovascular events in patients with type 2 diabetes mellitus: ameta-analysis of randomized trials. JAMA 2007;298:1180-8.
Both rosiglitazone and pioglitazone are known to increase the risk of congestive heart failure
Singh S, Loke YK, Furberg CD. Thiazolidinediones and heart failure: ateleo-analysis. Diabetes Care 2007;30:2148-53.
However, the risk of ischaemic cardiovascular events seems to have been mainly associated
Loke YK, Singh S, Furberg CD. Long-term use of thiazolidinediones
with rosiglitazone rather than pioglitazone
and fractures in type 2 diabetes: a meta-analysis. CMAJ2009;180:32-9.
Any distinct differences between the cardiovascular effects of the thiazolidinediones have yet
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Green S, eds. Cochrane handbook for systematic reviews of
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11 Davies HT, Crombie IK, Tavakoli M. When can odds ratios mislead?
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12 Cates CJ. Dr Chris Cates EBM website. 2010. www.nntonline.net. 13 Deeks JJ, Higgins JP, Altman DG. Analysing data and undertaking
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nificant beneficial outcomes may occur, one cannot
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assume that reporting bias is similarly focused on sig-
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15 Brownstein JS, Murphy SN, Golfine AB, Grant RW, Sordo M, Gainer V,
competing interests that emphasise interpretation and
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rosiglitazone.44 Finally, we had insufficient data to
16 Dormuth CR, Maclure M, Carney G, Schneeweiss S, Bassett K,
assess effects on stroke or death from cardiac causes.
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17 Graham DJ, Ouellet-Hellstrom R, MaCurdy TE, Ali F, Sholley C,
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18 Hsiao FY, Huang WF, Wen YW, Chen PF, Kuo KN, Tsai YW.
but statistically significant increase in the odds of myo-
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19 Juurlink DN, Gomes T, Lipscombe LL, Austin PC, Hux JE,
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authorities should carefully consider these results in
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20 Koro CE, Fu Q, Stender M. An assessment of the effect of
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type 2 diabetic patients. Pharmacoepidemiol Drug Saf2008;17:989-96.
Contributors: YKL, CSK, and SS developed the concept and protocol for
21 Lipscombe LL, Gomes T, Levesque LE, Hux JE, Juurlink DN, Alter DA.
the review. CSK and YKL abstracted and analysed data. YKL, CSK, and SS
Thiazolidinediones and cardiovascular outcomes in older patients
wrote the manuscript. YKL had full access to all of the data in the study,
with diabetes. JAMA 2007;298:2634-43.
takes responsibility for the integrity of the data and the accuracy of the
22 Margolis DJ, Hoffstand O, Strom BL. Association between serious
data analysis, and is the guarantor.
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Funding: SS is supported by grant number 1KL2RR025006-03 from the
Pharmacoepidemiol Drug Saf 2008;17:753-9.
23 Pantalone KM, Kattan MW, Yu C, Wells BJ, Arrigain S, Jain A, et al. The
NCRR, a component of the National Institutes of Health (NIH), and NIH
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and overall mortality, in type 2 diabetic patients receiving
collection, management, analysis, and interpretation of the data; and
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preparation, review, and approval of the manuscript was independent of
retrospective analysis. Acta Diabetol 2009;46:145-54.
any sources of funding. Its contents are solely the responsibility of the
24 Stockl KM, Le L, Zhang S, Harada AS. Risk of acute myocardial
authors and do not necessarily represent the official view of NCRR or NIH.
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Competing interests: All authors have completed the Unified Competing
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Interest form at http://www.icmje.org/coi_disclosure.pdf (available on
25 Tzoulaki I, Mokokhia M, Curcin V, Little MP, Millett CJ, Ng A, et al. Risk
request from the corresponding author) and declare that (1) they have no
of cardiovascular disease and all cause mortality among patients
relationships with any company that might have an interest in the
with type 2 diabetes prescribed oral antidiabetes drugs:
submitted work in the previous three years; (2) their spouses, partners,
retrospective cohort study using UK general practice research
or children have no financial relationships that may be relevant to the
submitted work; and (4) they have no non-financial interests that may be
26 Walker AM, Koro CE, Landon J. Coronary heart disease outcomes in
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Data sharing: No additional data available.
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