Epi test 1

Types of prevention 

Primary prevention, secondary prevention and tertiary prevention

Primary prevention: preventing disease before it happens 

• Healthy individuals 

• Prevent exposure (tobacco, pesticides) 

• Immunize against a disease 

• Promote healthy behaviors 

• (most effective but often most difficult to implement, especially for chronic diseases)

Secondary prevention: catching disease at an early, asymptomatic stage

• Requires knowledge of the natural history of the disease 

• Screening (colonoscopy, PAP smear) 

• Good idea when early treatment is more effective (breast cancer screening) 

• Helps stem transmission 

• Downsides: costly, invasive, over-treatment

Tertiary prevention 

• Prevention of health deterioration in those already diagnosed with a disease 

• Requires clinical data and patients 

• May involve pharmacological, behavioral or other interventions  

True or false: If two factors are strongly associated with each other, one must be causing the other:

false

What is the causal relationship between obesity and diabetes?

-neither necessary nor sufficient

Necessary cause:

without the factor, disease never develops (factor is necessary) 

Sufficient cause:

in presence of certain factor (s), disease always develops (a condition with which the effect must occur)

Necessary AND sufficient:

one to one relationship of exposure to disease, rare: largely theoretical, fatalistic 

Necessary but not sufficient:

 necessary factor but not sufficient in and of itself, common for many infectious diseases 

Sufficient but not necessary:

factor alone definitely produces disease…but so can other things 

Criteria for determining causality 

Temporal: exposure before outcome, strength:  measure of association, dose-response: > exposure => likelihood of outcome, except with thresholds, consistency: different studies and populations, biological plausibility: coherence with biologic knowledge, alternate explanations, cessation of exposure/experiment, coherence with other knowledge and specificity of the association

what type of study provides a ‘snapshot’ of the population

cross sectional

which of the following studies begins by identifying those with disease (cases)?

case control

A group of 1,500 college students from UCSD were followed for 6 months to investigate whether or not students who decided to routinely self-test for covid had a smaller risk of becoming infected with COVID-19. What type of study is this?

cohort

Descriptive

description of the occurrence of a disease in a population. Generates hypotheses

Analytical

analyzes relationships between health status and other variables (exposures). Includes a comparison group. Tests hypotheses.

Cohort

Long follow-up, Expensive, Large samples, Not good for rare diseases, Risk factors, Calculate incidence, Attrition/loss to follow-up

case control

Quick, Inexpensive, Small samples, Rare diseases, Uses records, Matched controls, Prone to bias

cross sectional

A design in which members of a specified population are assessed for

both exposure(s) and outcome(s) at a single point (or period) in time.

cross sectional - the bad

Bias can occur in the selection of participants or timing of survey, long lasting diseases are confusing, not suitable for rare diseases

ecological

Observational study in which the unit of measure is a population or group rather than an individual