CAUSE AND EFFECT Flashcards
What is a sufficient cause?
A factor or combination of several factors that will inevitably produce disease.
What is a component cause?
A factor that contributes towards disease causation but is not sufficient to cause disease on its own
What is a necessary cause?
Any agent (or component cause) that is required for the development of a given disease (like specific infectious agent)
In the book ‘Who sank the boat’ what type of cause involved the sinking of the boat?
Each animal was a component cause and together they created a sufficient cause. e.g. thrombosis leading to heart attack usually occurs if there is already a blockage in blood vessel or it is damaged.
What is the Bradford Hill criteria?
Temporality Plausibility Consistency Strength Dose Response Reversibility
What is temporality?
Exposure occurs before the disease can occur (this is definite)(e.g. tb, exposure to the bacteria occurs before the disease) (in any infectious disease)
What is reversibility?
- If you remove the exposure then you reduce the outcome e.g. If you remove saturated fats from diet you reduce risk of heart disease, reduce alcohol consumption and reduce risk of liver problems
What is dose response?
- Change dose of something and it changes the outcome (so if you increase dose, then increases chance of outcome, or if you increase dose of antibiotics disease decreases and health increases) (also radiation poisining)
What is plausibility?
Consistent with other knowledge (reinforces the body of evidence)
What is consistency?
Many studies give the same findings (e.g. trial of a new drug- multiple trials showed that the drug is effective)
What is strength association?
Relative risk. The higher or lower the risk, the greater the relationship is causal.
What is the condition for the Baseline Risk being the same in the intervention group as the control group?
That the groups are selected RANDOMLY
What is prevalence?
What PROPORTION of the population has the disease at a SPECIFIC POINT IN TIME (SNAPSHOT)
e.g. 160 of every 100 000 people in Europe has HIV at the end of 2007
Can prevalence also be measured in a specified period?
YES!! This is called period prevalence (combines prevalence and incidence)
What does prevalence measure the amount of?
DISEASE in a population at a given time
What is the equation for prevalence?
(number of people with disease at given point in time)/(total number of people in population) - it has no units; just proportion or percentage
Is prevalence rate a true rate?
NO because true rates include units of TIME
What is incidence?
Measures HOW QUICKLY people are catching the disease
“RATE of occurrence of NEW cases in a given PERIOD in a SPECIFIED POPULATUION.”
- Express it as either’ Rate (incidence rate) or proportion (culmulative incidence)
Is time a factor in incidence?
YES!! (so is a true rate)
What does incidence consider?
Only NEW infections!
What is the formula?
Number of people who develop the disease in one year/ Average number of people in population
What is an incidence rate good for and what is formula?
Underlying forces driving a disease
- It is ‘number of new cases/total person time of observation/risk”
What is prevalence good for?
Measuring diseases that have gradual onset and long duration (e..g type 2 diabetes and osteoarthritis_
What types of factors are part of descriptive epidemiology?
Prevalence, incidence and cumulative incidence