Measuring Health and Disease Flashcards
List four factors which require accurate measurement of disease occurrence and outcomes to be fully understood.
Impact on the population
Identifying risk factors
Informing public health interventions
Evaluating effectiveness of healthcare programs
What elements constitute a ‘clear case definition’?
Standardised criteria that helps to identify individuals/groups/population affected by the health problem/phenomena under study
Who (age, race, gender)
When (seasonal patterns, trends over time)
Where (clusters and spread)
Name four sources of health information.
Surveillance systems
Laboratory data
Health records
International organisations
List four factors which affect levels of disease occurrence.
Social and behavioural (lifestyle, access to healthcare)
Occupational (work-related risks)
Age and gender
Racial and ethnic
Define epidemiological ‘measures’.
Measures are used to relate the number of cases of disease (numerator), or health outcome to the size of the source population (denominator) in which they occurred
What variable is the numerator?
Number of cases of disease
What variable is the denominator?
Size of the source population
True or false: only one of the numerator and denominator variables needs to be defined.
False
Describe epidemiological counts.
Also referred to as ‘frequencies’
Used for extremely rare conditions
Count is merely a number
Data is retrieved from surveillance data
Not useful when comparing populations, as the denominators are different
Describe epidemiological ratios.
Relationship between two numbers
Usually expressed as x/y x 10n , e.g., number of stillbirths per thousand live births
Numerator is not part of the denominator
Discuss epidemiological proportions.
Fraction of a population, or a comparison of a part to the whole
A ratio in which the numerator (x) is included in the denominator (y)
Usually expressed as x/y x 10n, e.g., the number of foetal deaths out of the total number of births
Answer is often read as a percentage
Describe epidemiological rates.
How frequently an event happens in a specific population over a certain time frame, e.g., the number of new cases of Parkinson’s disease which develops per 1000 person-years of follow-up
Time, place and population must be specified for each type of rate
In a rate, numerator is not a subset of the denominator
Examples include birth rate, growth rate, accident rate
Frequency across different groups of people, places and time periods
List three different types of rates.
Crude rates
Category-specific rates
Age-adjusted rates
Both rates and ____________ are often used in public health to quantify mortality and morbidity.
Proportions
What is incidence?
The measurement of new cases
State six features of incidence.
Considered a rate
Time is essential
It provides information about the risk of developing the disease
Calculated for a given time period
Usually expressed as per 1000 or 100,000 people
Reflects risk of disease or condition
What term is synonymous with incidence rate?
Cumulative incidence
List features of cumulative incidence.
Measures the denominator only at the beginning of a study
Applies to dynamic populations (e.g., some people are born, die, or move in or out of a region)
Looks at each person in a population, and determines how long they are at risk
Numerator remains the same, denominator is now the sum of person-time (expressed in months or years) at risk
Name two other incidence quantifications.
Attack rate
Years of observation (incidence density)
What is prevalence?
The measurement of existing illness
List six points regarding prevalence.
Prevalence measures the total number of cases (both new and existing) of a disease in a population at a specific point in time
It provides insight into the overall burden of the disease
Considered a proportion
All subjects who appears in the numerator must also appear in the denominator
Point prevalence refers to a particular instance in time
Period prevalence accounts for a particular interval of time (existing cases, together with new cases)
List six features which increase prevalence.
Longer duration of the disease
Lifespan increased with treatment
If incidence increases
Immigration of new cases
Improved reporting
Emigration of healthy individuals
What are mortality indicators?
Measures of the frequency of occurrence of death in a defined population during a specified period of time
Mortality indicators, in the context of a ________ _____, do not take into account that the chance of dying varies with age, sex, race, etc..
Crude rate
True or false: mortality indicators are age-specific, but not necessarily cause-specific.
False
What are case fatalities?
Proportion of cases with a specified disease or condition, who die within a specified time, and a measure of disease severity
A _________ p-value means that observed differences were very unlikely to have occurred by chance, e.g., a p-value of 0.05 indicates that there was only a 5% chance that the observed differences between the two estimates under comparison occurred by chance alone.
Small
