CATEGORIZATION%20AND%20CLASSIFICATION%20OF%20HEALTH%20STATES

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CATEGORIZATION AND CLASSIFICATION OF HEALTH STATES

• Nigel Paneth

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HUMAN HEALTH STATES
1. DEATH 2. DISEASE 3. DISABILITY 4.
DESTITUTION
REALM OF PUBLIC HEALTH
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5. DYSFUNCTION 6. DISCOMFORT
REALM OF POSSIBLE BIOLOGICAL HAZARD
A seventh state is DISSATISFACTION - sometimes of
public health significance
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HEALTH STATES OF PUBLIC HEALTH IMPORTANCE

• 1. DEATH -Not whether, but when. 
• 2. DISEASE - A cluster of signs, symptoms and
  laboratory findings linked by a common
  patho-physiologic sequence, and that cause human
  distress.
•  3. DISABILITY and HANDICAP - Difficulty in
  performing expected functions, especially those
  important to ordinary human life, i.e.
  interfering with work, activities of daily
  living, etc.
•  4. DESTITUTION - The economic burden imposed by
  a health state.

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Human health states perhaps indicative of a
biological effect, but which do not, in
themselves, constitute public health entities

• 5. DYSFUNCTION - Poor or subnormal performance on
  a test of some single or complex biological
  function.  
• 6. DISCOMFORT Uncomfortable symptoms such as
  dizziness, nausea, fatigue, but short of a
  specific disease.

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THREE WAYS OF EXPRESSING HUMAN ILL-HEALTH

• DISEASE
• ILLNESS
• SICKNESS

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• DISEASE
• A cluster of signs, symptoms and laboratory
  findings linked by a common patho-physiologic
  sequence. Most epidemiology is about disease.
• ILLNESS
• The subjective state of the individual who feels
  aware of not being well. The ill individual may
  or may not be suffering from disease.
• SICKNESS
• The social role assumed by an individual
  suffering from an illness.

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OTHER TERMS FOR ILL-HEALTH

• When the signs and symptoms have not yet clearly
  been placed in a common pathophysiologic sequence
  the disease is referred to as a SYNDROME.
• Diseases of a chronic nature are sometimes
  called CONDITIONS, especially if they are present
  since birth (although this distinction between
  disease and condition is not always emphasized,
  and the terms are often used interchangeably).

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SPECTRUM OF DISEASE

• The point at which disease comes to medical
  attention may be anywhere along a SPECTRUM.
  Characteristically, population-based studies see
  a BROADER SPECTRUM OF DISEASE than do studies
  based on cases diagnosed in medical settings.
  This is important when we consider sampling next.

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SPECTRUM OF DISEASE

• 1. EXPOSURE  
• 2. SUBCLINICAL PATHOLOGIC CHANGES (in
  apparent infection especially important)
• 3. FIRST SYMPTOMS OR SIGNS/MILD DISEASE (usually
  diagnosed in outpatient setting)
• 4. MORE SEVERE DISEASE (may first
  be diagnosed in in-patient setting)
• 5. DEATH OR RECOVERY

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Diseases are usually classified either by
clinical manifestations or by etiology
CLASSIFICATION
DATA USED
EXAMPLE
signs/symptoms linked by common pathology
Stroke Heart Attack Cancer
MANIFESTATIONAL (or CLINICAL)
Fetal Alcohol Syndrome Lead Poisoning
ETIOLOGICAL
Presumed cause
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• Manifestation classifications are often more
  useful for treatment and management.
• Etiologic classifications are more useful for
  prevention.

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FUNCTIONAL CLASSIFICATION OF HUMAN HEALTH STATES
TYPE
NATURE OF INCAPACITY
EXAMPLE
Physical abnormality
Arthritis
IMPAIRMENT
Inability to use fingers for fine tasks
DISABILITY(activity limitation)
Inability to perform a human function
HANDICAP (participation restriction)
Inability to perform a social role
Cannot work as a seamstress
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Because epidemiology is interested in CASES OF
DISEASE, it does not (usually) study the
epidemiology of

• symptom inventories
• abnormal laboratory tests
• health behaviors
• medical care

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Major exceptions where the test or behavior is
closely linked to the disease, or a major risk
factor for disease.
Example 1 - SEROEPIDEMIOLOGY - the study of the
prevalence of antibodies to a specific infectious
agent.
Example 2 - Hypertension, smoking,
hypercholesterolemia
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Epidemiology is often interested in biological
phenomena with normal distributions.
Examples

• BLOOD PRESSURE
• BIRTH WEIGHT
• ADULT WEIGHT
• INTELLIGENCE QUOTIENT (IQ)

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How is disease defined for such normally
distributed measures? Because epidemiology is
interested in cases of illness, it is generally
more interested in TAILS OF THE DISTRIBUTION than
in the entire distribution. Disease states are
linked to the tails of the distribution of some
normally distributed phenomena.
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Epidemiology contrasted with other scientific
approaches

• The physiologist studies blood pressure, the
  epidemiologist studies hypertension.
• The psychologist studies IQ, the epidemiologist
  studies mental retardation.
• The nutritionist studies adult weight, the
  epidemiologist studies obesity.

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