Cardiovascular Epidemiology: Definitions Historical Perspectives and Assessing Risk of CVD Recent trends and population differences in CHD and CHD risk factors

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Cardiovascular EpidemiologyDefinitionsHistori
cal Perspectives and Assessing Risk of
CVDRecent trends and population differences in
CHD and CHD risk factors

Nathan Wong
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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

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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)

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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

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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 large-scale
  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.

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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 1980s 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.

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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.

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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.

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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

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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)

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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.

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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.

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1980-1996 Trends in Ischemic Heart Disease and
Stroke (source NCHS)
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Prevalences of Major CHD Risk Factors NHANES I
(1976-1980) and NHANES III (1988-1994) Males
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Prevalences of Major CHD Risk Factors NHANES I
(1976-1980) and NHANES III (1988-1994) Females
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Prevalences () of Major CHD Risk Factors
California, Behavioral Risk Factor Surveillance
System, 1996-1997
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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

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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