Updated: 12/28/2021

# Other Measures Of Disease Occurrence

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• Snapshot
• There is a city with a population of 500,000. There are 20,000 women of childbearing age. In the year 2020, there are 20 maternal deaths and 200 live births. The maternal mortality rate is 20/200 = 0.1.
• Introduction
• Overview
• in addition to prevalence and incidence, there are other methods of measuring the occurrence of disease
• Crude mortality rate
• describes the total number of deaths per years per 1,000 people
• equation
• number of deaths/total population size
• Cause-specific mortality rate
• describes the mortality rate caused by a certain disease/cause
• e.g., aggressive malignancy
• equation
• number of deaths by a certain disease/total population size
• Case-fatality rate
• equation
• number of deaths by a certain disease/total population affected by the disease
• Attack rate
• a type of incidence measure that is usually used in the epidemiology of infectious disease
• e.g., gastrointestinal infection in patients caused by contaminated food
• equation
• number of patients with the disease/total population at risk
• Maternal mortality rate
• equation
• number of maternal deaths/number of live births
• Crude birth rate
• equation
• number of live births/total populations size
•  Prospective and Retrospective Studies Prospective studiespatients enrolled before data collectionparticipants followed over timedata collected on exposures and outcomes as they ariseRetrospective studiesinvolve collecting historical information from a sample of patientsenrollment occurs after exposure and outcome have already occurred Case-Control Study Retrospective (almost always)Compares patients with and without disease to asses their odds of a certain exposureOdds ratio (OR) is measure of disease associationOR= odds of exposure among cases/odds of exposure in non-cases = ad/bcodds of exposure among cases=# cases with exposure/# cases without exposure = a/codds of exposure among non-cases=# non-cases with exposure/# non-cases without exposure=b/d"How much more likely is it that patients with cirrhosis have been exposed to heavy alcohol use compared to controls?" Cohort Study Can be eitherprospectiveorretrospectiveCompares groups with and without an exposure to assess associations with subsequent diseaseRelative risk (RR) is measure of disease associationRR= incidence rate in exposed group/incidence rate in unexposed group = [a/(a+b)]/[c/(c+d)]incidence rate in exposed group=# of exposed cases/(# total exposed cases and non-cases) = a/(a+b)incidence rate in unexposed group=# of unexposed cases/(# total unexposed cases and non-cases)=c/(c+d)"How much more likely are patients to develop cirrhosis if they are exposed to heavy alcohol use?" Cross-Sectional Study Exposure and outcome are assessed simultaneouslyAscertains association not causalityPrevalenceis measure of disease association"How much higher is the proportion of cirrhosis patients with heavy alcohol use compared to those without cirrhosis?"