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Cardiovascular Epidemiology:
Definitions
Historical Perspectives and Assessing
Risk of CVD
Recent trends and population differences
in CHD and CHD risk factors
Nathan Wong
Definitions
• CARDIOVASCULAR DISEASE or CVD
includes CORONARY ARTERY DISEASE and
other cardiac conditions (congenital,
arrhythmias, and congestive heart failure)
• CORONARY ARTERY DISEASE (CAD) or
CORONARY HEART DISEASE (CHD) (often
broadly referred to as ISCHEMIC HEART
DISEASE (IHD): primarily myocardial
infarction and sudden coronary death, broader
definition may include angina pectoris,
atherosclerosis, positive angiogram,
revascularization, and myocardial infarction
Definitions (cont.)
• REVASCULARIZATION includes coronary artery
bypass graft (CABG), percutaneous transluminal
coronary angioplasty (PTCA), stent, and atherectomy
• CEREBROVASCULAR DISEASE includes stroke
(ischemic or hemorrhagic) and transient ischemic
attack (TIA)
• PERIPHERAL VASCULAR DISEASE includes
carotid artery disease and intermittent claudication
• SURROGATE MEASURES include: carotid intimal
medial thickness (IMT), coronary calcium,
angiographic stenosis, brachial ultrasound flow
mediated dilatation (FMD)
Tools for Diagnosis of CHD
• Medical history: risk factors, including family
history, assessment of angina pectoris (Rose
questionnaire)
• Electrocardiogram (12-lead resting)
• Exercise stress ECG or thallium ECG
• Echocardiogram (m-mode evaluation of wall
thickeness, LV hypertrophy, 2D evaluation of
wall motion abnormalities, ejection fraction)
• Nuclear testing (sestamibi scans)
• Coronary angiography
Historical Perspectives of CVD
Epidemiology
• Concept of “risk factors”, coined by
Framingham Heart Study, involved gaining
understanding of factors predisposing to
occurrence of CVD
• Framingham Heart Study was the first largescale epidemiologic study, begun in 1948 among
5,209 men and women.
• First demonstrated epidemiologic relations of
cigarette smoking, blood pressure, and
cholesterol levels to incidence of CHD.
Misconceptions Corrected
• Blood pressure originally thought to be normal to rise
with age to ensure adequate perfusion as arteries
narrowed, and elevated diastolic blood pressure felt to
cause all problems
• Skepticism about cholesterol as a risk factor for CHD
persisted into the 1980’s until epidemiologic research and
clinical trials proved otherwise
• Before epidemiologic studies, physical activity was
thought to be dangerous to CHD candidates
• Left ventricular hypertrophy now shown to be an
ominous harbinger to CHD rather than as a
compensatory response to hypertension.
• CHD is a multifactorial process involving many
predisposing factors.
Cardiovascular Risk Profiles
• Risk factors easily obtained during an office visit
can help assess future risk of CHD
• For CHD, these include serum cholesterol,
hypertension, diabetes, ECG-LVH, and cigarette
smoking, and from more recent profiles, LDL-C
(instead of total cholesterol) and HDL-cholesterol.
• Tables provide easy determination of 10-year risk of
CHD, stroke, peripheral vascular disease, and
congestive heart failure.
• A simplified version of the CHD table allows use of
JNC-VI and NCEP classifications of blood pressure
and LDL-cholesterol levels.
Cardiovascular Risk Profiles
(continued)
• These tables show risk to be additive across
categories of two or more risk factors
• Risk increases across levels of one risk factor
(e.g., cholesterol) may be much greater if
other risk factors (e.g., diabetes and
hypertension) are present, than if no other
risk factors are present
• Short-term (e.g., 10 years) risk may, however,
not relate to longer, lifetime risk.
Differences and Trends in CHD
and CHD Risk Factors across
Populations
• International comparisons in incidence
• Comparisons across regions of the United
States and among ethnic groups
• Trends in CHD incidence across countries
• Trends in CHD risk factors and ethnic
differences
International Comparisons in
CVD Morbidity and Mortality
• CVD accounts for 25-45% of deaths
among different countries
• CVD death rates (per 100,000) range
from 1310 in Russia to 201 in Japan (6.5
fold difference) in men and from 581 in
Russia to 84 in France (7-fold difference)
• USA ranks 16th for both men (413) and
women (201)
CHD Morbidity and Mortality
in the USA
• In 1995, 960,000 in USA died from CVD, 42% of all
deaths, leading cause in men over age 45 and women
over age 65.
• 58 million or 20% of population have some form of
CVD.
• Half of CVD deaths due to CHD, 16% due to stroke.
• CHD deaths (per 100,000) greatest in New York (180),
least in New Mexico (82). California ranks 28th (125).
• Stroke deaths (per 100,000) greatest in South Carolina
(63), least in New York (31). California ranks 27th (43).
• Economic costs of CHD estimated at $274 billion in
1998.
Secular Trends in CHD and
Stroke Mortality
• From 1985-1992, greatest annual decline
(6-7%) in CHD seen in Israel among men
and France among women, USA
intermediate (4%), increases in Poland
and Romania.
• Stroke death rates declined most in
Australia, Italy, and France (8-9%), USA
about 3%.
1980-1996 Trends in Ischemic Heart
Disease and Stroke (source: NCHS)
0
-5
-10
-15
Percent -20
Change -25
-30
-35
-40
-45
Males
Females
Native Americans
Asians/PI
Blacks
Hispanics
Whites
IHD
Stroke
Prevalences of Major CHD Risk Factors:
NHANES I (1976-1980) and NHANES III
(1988-1994): Males
60
50
40
30
20
1976-80
1988-94
Smoking
High
Cholesterol
Obesity
0
Overweight
10
Prevalences of Major CHD Risk Factors:
NHANES I (1976-1980) and NHANES III
(1988-1994): Females
Smoking
High
Cholesterol
Obesity
1976-80
1988-94
Overweight
50
45
40
35
30
25
20
15
10
5
0
Inactivity
Smoking
High
Cholesterol
Overweight
35
30
25
20
15
10
5
0
Hypertension
Prevalences (%) of Major CHD Risk
Factors: California, Behavioral Risk Factor
Surveillance System, 1996-1997
Migrant Studies
• Ni-Hon-San Study showed Japanese living
in Japan to have the lowest cholesterol
levels and lowest rates of CHD, those living
in Hawaii to have intermediate rates for
both, and those living in San Francisco to
have the highest cholesterol levels and
CHD incidence
CHD Incidence: 1940 vs. 2000
Age-Adjustment Standards
• Because age is one of the strongest predictors of CHD, it
is an important confounder to consider when making
comparisons across groups (gender, ethnic, geographic)
• Official US statistics have used the 1940 age distribution
as the standard, but with more older age adults, the 2000
standard is being used, resulting in substantial increases
in incidence, nearly two-fold higher than when using the
1940 standard
• CHD incidence 1995 about 375/100,000 using the 2000
standard, compared to 180/100,000 using the 1940
standard