Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT00064545 |
| Other study ID # |
1227 |
| Secondary ID |
5R01HL074377 |
| Status |
Completed |
| Phase |
N/A
|
| First received |
July 8, 2003 |
| Last updated |
December 11, 2012 |
| Start date |
July 2003 |
| Est. completion date |
June 2008 |
Study information
| Verified date |
December 2012 |
| Source |
University of North Carolina, Chapel Hill |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
United States: Federal Government |
| Study type |
Observational
|
Clinical Trial Summary
To evaluate common genetic variations, that in combination with exposure to tobacco smoke,
may modify the risk of atherosclerosis.
Description:
BACKGROUND:
While cigarette smoking is a well-established and potent risk factor for atherosclerotic
vascular disease, individual susceptibility to smoking varies considerably, suggesting
modifiers such as genomic variation. Several key enzymes involved in the activation and
detoxification of mutagenic tobacco smoke compounds, oxidative stress, and DNA damage are
expressed in the tissues of the heart and vasculature and represent mechanistic pathways for
tobacco-induced pathology. Many of these enzymes have common polymorphisms (greater than or
equal too 10% prevalence in the population) with known functional effects. Although
restricted to a few enzymes and hampered by shortcomings in design, a small number of
studies have suggested that enzymatic activation and detoxification of tobacco smoke
modifies the risk of certain cardiovascular outcomes associated with cigarette smoking.
DESIGN NARRATIVE:
The genetic epidemiology study will evaluate common genetic polymorphisms that, in
combination with exposure to tobacco smoke, may modify the risk of atherosclerosis and its
clinical sequelae. An average of six polymorphisms, selected on the basis of their
prevalence and functional significance, expression in relevant tissues, evaluation in
previous studies and biologic plausibility, within 19 genes involved in activation,
detoxification, oxidative stress, and DNA repair pathways will be evaluated as an ancillary
study to the Atherosclerosis Risk in Communities (ARIC) study. In this well-characterized,
bi-ethnic cohort of 15,792 men and women under active follow-up since 1987-89 (completeness
of follow-up 96%), five endpoints quantifying subclinical atherosclerosis and validated
clinical atherosclerotic events will be studied in case-cohort/case-control mode: incident
coronary heart disease, carotid atherosclerosis, peripheral arterial disease, incident
stroke, and MRI-detected cerebral infarcts. The study is well designed to study how DNA
sequence polymorphisms can promote or inhibit the atherogenic effects of smoking and the
risk of clinical events, and to contribute new knowledge on the role of genetic variation in
the response to environmental insults and toxicants.
A case-cohort or case-control approach will be taken, using data from the Atherosclerosis
Risk in Communities (ARIC) study. Approximately 20 polymorphisms will be examined in
relation to five cardiovascular disease (CVD) endpoints. The polymorphisms to be examined
are classified as variants of either a) Phase I (activation) enzymes, b) Phase II
(detoxification) enzymes, c) oxidative stress enzymes, or d) DNA repair enzymes. The CVD
endpoints include incident coronary heart disease (CHD) cases (n=1,101), incident stroke
cases (n=323), prevalent peripheral artery disease (PAD) (n=237 cases), carotid
atherosclerosis determined by MRI (n=504 cases), and cerebral infarcts (n=237cases).
Controls will consist of 1,062 controls selected at visit 1, and 237 visit-3 controls for
the cerebral infarct cases. The statistical approach will be based on the proportional
hazards regression for incident CHD and stroke endpoints, and logistic regression for the
other CVD outcomes. Both additive and multiplicative forms of interaction will be tested.
