Fraction of a group of people possessing a clinical condition or outcome at a given point in time

Prevalence

Point vs Period Prevalence

Point - single point in time

Period - defined period

Fraction of a group of people initially free from outcome of interest that develops condition over given point in time (new cases)

Incidence

Formula for incidence

New cases in period of time / Susceptible people without disease at beginning of period

Formula for prevalence

Existing cases at defined time / Population (All people, cases and non-cases)

Type of study used to measure incidence

Cohort Study

Type of study used to measure prevalence

Cross-Sectional Study

Relationship between duration of disease, prevalence, and incidence

Prevalence/Incidence = Duration (steady state) Prevalence = Incidence x Duration

In words: Higher duration = more likely to be caught by prevalence study

Proportion of people having a disease who die from it

Case fatality rate

Proportion of people having a disease who survive it

Survival Rate

Formula for infant mortality rate

Number of deaths in year of children <1 yr

over

Number of live births in the same year

Formula for perinatal mortality rate

Number of stillbirths and deaths in first week of life per 1000 livebirths

Formula Maternal Mortality Rate

Number of maternal deaths related to childbirth in a given year

over

Number of live births in the same population during same year

TRUE OR FALSE: Infant mortality rate and maternal mortality rate are approximations of incidence?

TRUE

Approach to studying incidence in a dynamic population

Incidence Density (Person Years) Take into account time each person is part of the population/at risk

In measuring rates for cervical cancer - what is the appropriate denominator?

Women who are susceptible (with cervix, no hysterectomy done)

A concentration of new cases in time

Epidemic

A widespread disease globally

Pandemic

A disease limited to certain places

Endemic

TRUE OR FALSE: Prevalence studies provide good evidence for cause and effect

FALSE! -

only one point in time is measured, cant establish that conclusion yet