EXERCISE EPIDEMIOLOGY

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EXERCISE EPIDEMIOLOGY

• EVIDENCE OF PHYSICAL ACTIVITY AS AN INDEPENDENT
  RISK FACTOR

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EPIDEMIOLOGY-Definition

• Study of frequencies distributions of disease
  in human populations.
• Establish cause of disease means of its spread
  and mechanism for its surveillance.
• Comparison Contrast- see if groups
  characterized in one way (i.e, active vs
  inactive) can be differentiated by another factor
  (risk or occurrence of cardiovascular heart
  disease).

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Principles Applied in Research

• Statistical Association-significance between
  presumed cause effect.
• Temporal Sequence-assessed cause preceded the
  effect.
• Consistency- Findings cross age, gender, race,
  occupation, geography, economic status.
• Persistence-Follow-up studies should find similar
  trends.

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EPIDEMIOLOGY PRIN. CONT.

• Independence- In spite of other factors, does the
  exercise/CHD relationship hold.
• Dose-response-Does more exercise lower CHD.
• Specificity-exercise affects CHD more than any
  other disease (maybe types of cancer).
• Alterability-application of dose-response.
• Repeatability- multiple findings similar.
• Confirmation-Physiological consequence.

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Relative Risk Concept (RR)

• Compare the incidence of CHD of sedentary vs
  active population. If active group has lower
  incidence then RR is lt1.00. Higher incidence
  results in RRgt1.00.
• Confidence Interval- 95 CI means only 5 chance
  results aren't truly different. Sets upper and
  lower limits for separating RR in groups.
  Researchers report both RR and CI data.

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Types of epidemiological studiesI.
snap-shot-x-sectional.
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II. flashback-retrospective or casecontrol
study

• Recall personal histories of past phsical
  activity.
• Compare disease vs disease free group in terms of
  past activity.
• bias from already knowing outcome.

• Casdecontrol pairs of older Floridians.
• 568 pairs- 322 controls more active than cases.
• As casecontrol activity score 1.0, risk
  0.83.When score gt5, risk0.50.
• Scoregt10, risk0.30

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III. Motion Picture-Prospective

• Harvard Alumni-started in 1960, repeat collection
  through 1990s. Obtain data in advance of
  outcomes.
• Statistical association-Inc. activity Dec. risk
• Consistency-All age groups.
• Persistence- Several follow-ups
• Dose-response- Activity kcal and CHD rate
• Independence- correct for other risk factors.

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IV. Time-Lapse Experimental

• Randomized clinical trial-Take group and assign
  activity or sedentary lifestyle.
• Exercisers-1.9 developed CHD vs 4.3 in
  control.
• All MI- 5.3 vs 7.0
• Non-fatal MI- 4.5 vs 3.4
• MI death- 0.3 vs 2.4.

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V. Rerun, hypothetical

• What if groups had led better lives? What might
  be impact on changing CHD in population?

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VI. Futuristic-predictive

• How might longevity be affected with changing
  activitiy. Do you gain years based on making a
  sedentary person active.
• Need to use inactive vs active people for
  projection.
• 2.15 yr gain estimated for sedentary person who
  becomes active.