what are types of health indicators?
- Physical disease
- Mental illness (limited functional ability for activities of daily living due to a medical condition such as severe Alzheimer’s disease)
- Impairment or disability (limited functional ability for activities of daily living due to a medical condition such as cerebrovascular accident)
- Social well-being
- Service availability and provision
- Resource availability
types of statistics used in descriptive epidemiology
- Counts
- Ratios
- Proportions
- Percentages
- Rates
descriptive epidemiology: counts
- Number of cases
- Count
- Frequency
- No denominator
**when health indicators are reported as counts, it is important to know the number of cases and number of frequencies
descriptive epidemiology: ratios
- Ratios compare two things
- Divide the numerator by the denominator
- Expressed as X/Y or X:Y
- Numerator may or may not be part of the denominator
- The numerator and denominator may or may not be related
**key feature: ratio has a numerator and denominator
what are rates
- Frequency of an event in a population during a specified period of time
- Numerator is the number of people who experience an event
- Denominator is the number of people in the population
- Population is always specified
- Time period is always specified
- In a true rate, person-time is the unit (person-years)
**rates are important when you’re comparing the disease cases, occurrences, outbreaks in two different populations, groups at two different points in time at two different geographical areas
vitals sign
essential measures of health for individual patients
vital statistics
essential measures of health for a population
what are the three major categories of vital statistics
- Mortality
- Morbidity
- Natality
- The indices used are typically related to births and deaths because these data are more readily available than morbidity data
what is mortality rate?
a measure of the frequency of occurrence of death in a defined population during a specified interval
what is the crude mortality rate
the mortality rate from all causes of death for a population
what is infant mortality rate?
- Deaths of infants < 1 year of age
- Denominator is number of live births in the given time period
- Per 1,000 live births
- Single most widely used health indicator to compare nations
what is neonatal mortality rate?
- Deaths of infants < 28 days of age
- Denominator is number of live births in the given time period
- Live birth has a specific definition
- Per 1,000 live births
what is maternal mortality rate?
Deaths of cis-gender females due to pregnancy related causes anytime during pregnancy or during the first 42 days after pregnancy termination (regardless of the
duration of the pregnancy)
* Denominator is number of live births in the given time
period
* Per 100,000 live births
what is pregnancy related mortality?
- Death of a cis-gender female while pregnant or within 1 year of the end of a pregnancy (regardless of the duration) from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes.
- Denominator is number of live births in the given time period
- Per 100,000 live births
what is morbidity?
a measure of the frequency of
occurrence of disease or injury in a defined population during a specified interval.
what are rates adjusted to control?
to control confounding factors/variables
what are the two major measures of disease frequency?
incidence and prevalence
what is prevalence
Prevalence refers to the status of disease, not the onset
Prevalence measures all cases (old and new) at a specified period of time
what is point prevalence?
assessed at one specific point in time
- Single point in time
- Number of existing cases (old and new cases) on a certain date (e.g., January 1, 2015)
what is period prevalence
assessed during a certain period
- Period of time – days, weeks, months, years
- Start and finish times are specified (e.g., January 1, 2015 through December 31, 2015)
what are prevalence statistics often use for?
- policy and administrative decisions
- informs policy makers and the public about the burden of disease
- used in planning health services, both direct care and preventative services
- Prevalence statistics can provide some insight about possible factors associated with disease
- But, the causal relationship cannot be verified by prevalence data
- Useful for generating hypotheses
what is incidence?
- Incidence measures the rate at which people without a disease develop the disease during a specified period
- Incidence is a measure of the onset of disease
- Incidence measures the appearance of disease
- Incidence means new
- Note: The word “disease” can be substituted with injury or disability* Incidence describes only the number of new cases that occur during that time period of interest
- Measures the number of new cases of the health-related state (disease, injury) that occur during the specified time
- Does not include the pre-existing cases
what is the incidence proportion?
number of new cases of a disease in a specified time period/population at risk of the disease at the start of that time period
also called:
- risk
- attack rate
- probability of developing a disease
what is the incidence rate?
number of new cases of a disease in a specified time period/ time that each person was observed, totaled for all persons
* Also known as “Person-Time Rate”
* More difficult to calculate
* More accurate estimate of risk
* Accounts for incomplete data
