BIOL 437 Week Ten p.2 (Causality) Flashcards
direct causal association
- no intermediate factor
- more obvious
- elminating exposure will eliminate the adverse health outcome
ex. a trauma to the skin
indirect causal association
- involves one or more intervening factors
- often more complicated
ex. poor diet and stress may cause high BP, which can cause heart disease
factors of causation
- predisposing factors
- enabling factors
- precipitating factors
- reinforcing factors
predisposing factors
- factors already present that produce a susceptibility or diposition in the host to a disease or condition without actually causing it
ex. age, immune status, knowledge, beleifs
reinforcing factors
-help aggravate and perpetuate behaviours, disease, conditions, disability or death
positive reinforcing factors
- social support
- health education
- economic assistance
negative reinforcing factors
- negative peer influence
- poor economic conditions
enabling factors
- antecedants to behaviours, disease, conditions, disability or death
ex. services, living conditions, programs - can also be a result of lack of services or medical programs
precipitating factors
- essential to the development of diseases, conditions, injuries, disabilities and death
ex. infectious agent, lack of seat belt use, drinnking and driving, lack of helmet
evidence for causal relationship (Henle and Koch postulates)
- Organisms is always found with the disease
- Organism is not found in those without the disease
- Organism when isolated from one who has the disease and is cultured, produces the disease
direct observation
-lot of knowledge gained in this manner
inference
-essential to scientific acitivty
>not everything can be observed
latency
ex. long period between exposure to cigarettes and onset of lung cancer
induction
Example:
- 2-week long induction period of measles and its infectiousness: barrier to understanding transmission
- confoudned seasonality link
Test of operational hypothesis
- design study and collect data
- analyze data and make conclusions about study hypothesis
- modify hypotheses if needed
type 1 error
-when hypotheis is rejected but is actually true
type 2 error
-when hypothesis is not rejected but is actually false
falsification of a hypothesis (Karl popper)
-more informative than corroboration of a hypothesis
>a single counter example forces modification
>studies should attempt to refute rather than confirm hypothesis
-problematic in epidemiology