elegantly showed an association between a variant (SNP
rs1333049) on chromosome 9p21 and coronary artery disease
(CAD) severity represented by the number of coronary arteries
with Ͼ50% stenosis in 2 cohorts of CAD patients who did not
have diabetes mellitus (1). This provides novel evidence for an
inﬂuence on the extent of coronary arterial lesions by the 9p21
variant, which was identiﬁed recently by genome-wide association
studies to be a major genetic determinant that increases the risk of
Interestingly, several previous studies did not ﬁnd the association
between 9p21 and CAD severity deﬁned by the number of coronary
arteries with signiﬁcant stenosis (3–5). In their report, Dandona et al.
(1) speculated on several possible explanations, 1 of which is the
inclusion of CAD patients with diabetes mellitus in the previously
studies, which might confound and obscure the effect of 9p21 on
To investigate this possibility, we undertook analyses in a cohort of
CAD patients (mean age 63 years, n ϭ 1,094) recruited previously in
the SAS (Southampton Atherosclerosis Study) (6). The subjects had
Ͼ50% stenosis in at least 1 major epicardial coronary artery and were
all of European ancestry. When CAD patients with diabetes mellitus
(n ϭ 146) were excluded, we observed an association between the risk
allele (C allele) of the 9p21 SNP rs1333049 and increased risk of
3-vessel disease (3VD) deﬁned by Ͼ50% stenosis in the 3 major
coronary arteries (p ϭ 0.022) (Fig. 1). Logistic regression analysis
showed that each copy of the risk allele was associated with a 30%
increased risk of 3VD (odds ratio: 1.30 [95% conﬁdence interval: 1.04
to 1.63]) after adjusting for age, sex, smoking, hypertension, hyper-
cholesterolemia, lipid-lowering treatment, and body mass index.
However, when the CAD patients with diabetes mellitus were
included in the analysis, the relationship between SNP rs1333049 and
CAD severity became nonsigniﬁcant statistically (p ϭ 0.077). This
ﬁnding is in line with the possibility of an obscuring effect of diabetes
mellitus, suggested by Dandona et al. (1).
Thus, the results of our study support that there is an association
between 9p21 and CAD severity, arguing for the notion that the
9p21 variant predisposes to initiation as well as progression of
CAD (2). In addition, our data highlight the need for further
detailed studies to assess the effects of 9p21 on CAD phenotypes
and its potential interactions with other cardiovascular risk factors
such as diabetes mellitus.
Kenneth Chan, MPharm
Anna Motterle, MSc
Ross C. Laxton, BSc
*Shu Ye, MD, PhD
*Barts and the London School of Medicine
Queen Mary University of London
John Vane Science Building
London EC1M 6BQ
Please note: The authors are grateful for the support of the British Heart Foundation.
This work forms part of the research themes contributing to the translational research
portfolio of Barts and the London Cardiovascular Biomedical Research Unit, which
is supported and funded by the National Institute of Health Research.
1. Dandona S, Stewart AF, Chen L, et al. Gene dosage of the common
variant 9p21 predicts severity of coronary artery disease. J Am Coll
Cardiol 2010;56:479 –86.
2. Anderson JL, Horne BD. The 9p21 locus and coronary heart disease:
initiator, promoter, or precipitator? J Am Coll Cardiol 2010;56:487–9.
3. Anderson JL, Horne BD, Kolek MJ, et al. Genetic variation at the 9p21
locus predicts angiographic coronary artery disease prevalence but not
extent and has clinical utility. Am Heart J 2008;156:1155– 62.
4. Hinohara K, Nakajima T, Takahashi M, et al. Replication of the association
between a chromosome 9p21 polymorphism and coronary artery disease in
Japanese and Korean populations. J Hum Genet 2008;53:357–9.
5. Hiura Y, Fukushima Y, Yuno M, et al. Validation of the association of
genetic variants on chromosome 9p21 and 1q41 with myocardial
infarction in a Japanese population. Circ J 2008;72:1213–7.
6. Ye S, Dunleavey L, Bannister W, et al. Independent effects of the -219
GϾT and epsilon 2/ epsilon 3/ epsilon 4 polymorphisms in the
apolipoprotein E gene on coronary artery disease: the Southampton
Atherosclerosis Study. Eur J Hum Genet 2003;11:437–43.
We thank Mr. Chan and colleagues for the interest in our paper
(1). They are able to replicate the association of gene dosage of the
risk variant located at 9p21 and severity of coronary artery disease
(CAD) in the SAS (Southampton Atherosclerosis Study) when
diabetic patients are excluded from their analysis. However, when
diabetic patients are included, this association no longer achieves
statistical signiﬁcance. Given the ﬁndings of Doria et al. (2) that
poor glycemic control tended to amplify the risk association of
CAD with 9p21, we had postulated in our original paper that the
inability to demonstrate such an association in other cohorts might
potentially have been secondary to a confounding effect of diabetes
(1). The ﬁnding of Mr. Chan and colleagues would lend credence
to this hypothesis. We do recognize that further similar conﬁrma-
tory studies are required. However, these ﬁndings do underscore
the need for meticulous phenotyping in genetic association studies.
Furthermore, it demonstrates the potential complex interplay
Figure 1 Association of 9p21 Genotype With Severity of CAD
Presented in the column chart are percentages of patients with 3-vessel dis-
ease (3VD) (n ϭ 223) as a function of genotype. The p value was derived from
logistic regression analysis with adjustment for age, sex, smoking, hyperten-
sion, hypercholesterolemia, lipid-lowering treatment, and body mass index.
Patients with diabetes mellitus were excluded. CAD ϭ coronary artery disease.
JACC Vol. 57, No. 13, 2011
March 29, 2011:1496 –500