Epidemiology Measures of Morbidity and Mortality

Relative Risk/Risk Ratio

A comparison of the risk of some health related event such as disease or death between two groups

Morbidity

A measure of the disease in a population, either by the incidence or the prevalence of disease

Incidence Rate

A measure of the frequency of an event, such as a new case of an illness occurs in a population over a period of time

Mortality Rate

A measure of the frequency of occurrence (incidence) of specific causes of death in a defined population during a specific interval of time

Incidence Density Rate/Person-Time Rate

A measure of the number of new cases based on the amount of time a person remains in a disease-free state

Crude Mortality Rate/Crude Death Rate

A measure of the proportion of death in a population usually the mortality rate from all causes of death for a population

Crude Incidence/Cumulative Incidence/Incidence Proportion

A measure of the proportion of new cases over the lifetime of the study or the population

Post-Neonatal Mortality Rate

A ratio expressing the number of deaths among children from 28 days up to but not including 1 year of age during a given time period divided by the number of live births reported during the same time period expressed per 1,000 live births

Neonatal Mortality Rate

A ratio expressing the number of deaths among children from birth up to but not including 28 days of age divided by the number of live births reported during the same time period expressed per 1,000 live births

Infant Mortality Rate

A ratio expressing the number of deaths among children under 1 year of age reported during a given time period divided by the number of births reported in the same time period expressed per 1,000 live births

Child Mortality

A ratio expressing the number of deaths among children who die by the age of 5 per 1,000 live births per year

Attack Rate

A type of incidence when the occurrence of a disease among an at-risk population (susceptible population) increases greatly over a short period of time. Describes the percentage of people getting sick, usually to a specific exposure

Age-Specific Mortality Rate

Mortality rate related to a specific age group

Point Prevalence

The amount of a particular disease present in a population at a single point in time -- usually the present, but can be the past

Period Prevalence

The amount of a particular disease present in a population over a period (length) of time of the study. This includes the number of people that have the disease at the beginning of the study and those that get the disease during the period of the study

Survival Rate

The probability that a person will remain alive for a specific amount of time, usually measured as 1 year or 5 year rates

Prevalence

The proportion of cases or events or conditions in a given population

Case Fatality Rate

The proportion of persons with a particular condition (cases) who die from that condition

Lifetime Prevalence

The proportion pf people in a population to get a disease sometime in their lifetime based on the average lifespan

Mortality

The state of being mortal and susceptible to death

1. Shorter duration of the disease 2. High death/fatality rate 3. Decreased incidence 4. In-migration of healthy people 5. Out-migration of diseased people 6. Improved healthcare

In what ways can the prevalence of a disease be decreased?

1. Longer duration of disease 2. People living longer with the disease 3. Increase in new cases (incidence) 4. In-migration of diseased people 5. Out-migration of healthy people 6. Increased susceptible people 7. Better diagnosis methods

In what ways can the prevalence of a disease be increased?

1. Number of events 2. A population 3. Unit of time

What are the requirements for measuring the incidence of a disease?

D=number of people dying from a specific disease/A=number of new cases of the disease

What do the components of the case fatality rate equation (CFR=D/A) stand for?

A=Number of new cases/N=number of people present at the start of the study

What do the components of the crude incidence equation (CI=A/N) stand for?

A=number of new cases occurring during a given time period/PT=person time=days, months, or typically years

What do the components of the incidence density rate equation (ID=A/PT) stand for?

A=number of new cases occurring during a given time period/T=time period

What do the components of the incidence rate equation (IR=A/T) stand for?

C=Total number of cases (existing + new)/N=number of people in the population

What do the components of the prevalence equation (P=C/N) stand for?

ASMR=deaths in age group/population of age group

What is the equation for determining age-specific mortality rate?

CI=A/N

What is the equation for determining crude incidence?

CMR=all death/N total population

What is the equation for determining crude mortality rate?

ID=A/PT

What is the equation for determining incidence density rate?

IR=A/T

What is the equation for determining incidence rate?

MR=D/N

What is the equation for determining mortality rate?

P=C/N

What is the equation for determining prevalence?

CFR=D/A

What is the equation for determining the case fatality rate?

S=(A-D)/A

What is the equation for determining the survival rate?