Cross sectional

Question 1

Cross sectional
General info

Answer 1

Compares population on individual level.

• Snapshot of both Exposed and Diseased at one point in time (Prevalence)

Type: Descriptive & Analytic

Question 2

Cross sectional
Advantages

Answer 2

1. Common diseases. Prevalent & Long (Chronic)
2. Multi diseases & exposures or risk factors can be assesed
3. No loss to follow-up (Snapshot)
4. Inexpensive. Little time to conduct
5. Good for creating hypothesis
6. Permit determination of population characteristics at given moment (Prevalence)

Question 3

Cross sectional
Disadvantages

Answer 3

1. Not useful for rare or short-term diseases (May not be captured in snapshot)
2. Cannot establish causality
3. Temporal relationship unclear (Dont know who came first between, cannot infer temporality because E and D measured simultaneously)

Question 4

Cross sectional
Formula and interpretation

Answer 4

1. Total prevalence of disease (a+c)/(a+b+c+d)
2. Total prevalence of exposed (a+b)/(a+b+c+d)
3. Prevalence of disease in exposed a/(a+b)
4. Prevalence of exposed in diseased a/(a+c)
5. Prevlence Odds Ratio (POR) ` (a/b)÷(c/d)`
6. Prevalence Risk Ratio (PRR) (a/a+b)÷(c/c+d)

Question 5

Cross sectional
Prevalence Odds ratio (POR)

Answer 5

Describes if exposure is associated with odds of disease vs unexposed

Prevalence Odds Ratio (POR) ` (a/b)÷(c/d) * (a/b) odds of disease in exposed * (c/d)` odds of disease in unexposed

The odds of DEPRESSION among DRINKERS are 1.5 TIMES the odds of depression AMONG NON-DRINKERS

Interpretation of RISK ASSOCIATION:
* POR = <1 Exposure has asscn with low odds of disease vs unexposed
* POR = 1 Exposure not associated with odds of disease
* POR = >1 Exposure has asscn with high odds of disease vs unexposed

Question 6

Cross sectional
Prevalence Risk Ratio (PRR)

Answer 6

It looks at the actual risk of getting the disease if you are exposed

Prevalence Risk ratio (PRR) (a/a+b)÷(c/c+d)

• (a/a+b) risk of disease in exposed
• (c/c+d) risk of disease in unexposed

The risk of DEPRESSION among DRINKERS is 1.5 times the risk of DEPRESSION among NON-DRINKERS

Rare disease (<10% Prevalence) POR=PRR

Common disease POR>PRR

Interpretation of ACTUAL RISK:
* PRR = <1 Exposure associated with low risk (prevalence) of disease in exposed vs unexposed (Protective effect)
* PRR = 1 Exposure no effect (didnt prevent/harm)
* PRR = >1 Exposure associated with high risk (prevalence) of disease in exposed vs unexposed (Harmful effect)