206a - week 1: comparing disease frequency (10/2/25)

determinatnes

identify preventative, curatice, & caysative factors by comparing measures of disease frequency & calculating measures of assocaitoin

possible comparisons

index groups (exposed) vs comparison/reference group (unexposed)

measure of assoication

comparisons of measures of disease frequency

2 measures of association

• absoulute measure

• relative measure

absolute measure

calculate the DIFFERENCE b/w 2 measures of disease frequency

relative measure

calculate the RATIO of 2 measures of disease frequency

absolute measure of association: no association b/w expsure & disease than the risk diff (RD) is…

0

absolute measure of association: exposure is associated w/ increased risk of disease then the risk diff (RD) is…

> 0

absolute measure of association: exposure is associated w/ decreased risk of disease then the risk diff (RD) is…

< 0 

The Nurses’ Health Study is a longitudinal cohort study of
factors that influence women’s health. NHS researchers
investigated the hypothesis that hypertension increases the
risk of myocardial infarction (MI). Among 13,422 women with
hypertension, 117 had an MI over 10 years of follow-up.
Among 106,541 women without hypertension, 125 had an MI
during the same follow-up period

a. preval diff

b. risk diff

c. rate diff

risk difference

reltaive risk

represent all of the
classes of relative measures of association.
• “Relative risk” is often used interchangeably with “risk
ratio” (cumulative incidence ratio), because that is the most
commonly used relative measure of association.
o But pay attention to context

relative measure of association: no association b/w the exposure & disease, then the RR

= 1

relative measure of association: exposure is associated w/ increased risk of disease then the RR is…

> 1

relative measure of association: exposure is associated w/ decreased risk of disease, then the RR is…

< 1

The Nurses’ Health Study is a longitudinal cohort study of
factors that influence women’s health. NHS researchers
investigated the hypothesis that hypertension increases the
risk of myocardial infarction (MI). Among 13,422 women with
hypertension, 117 had an MI over 10 years of follow-up.
Among 106,541 women without hypertension, 125 had an MI
during the same follow-up period

A. Prevalence ratio
B. Risk ratio
C. Rate ratio

risk ratio

excess relative risk formula

(RR-1) x 100%

RD = absolute measure represents…

public health impact of exposure on disease occurence

RR = relative measure represents..

strenght or magnituve of the association b/w an exposure & a disease