Measuring and Describing Disease Flashcards
Define epidemiology
the study of the distribution and determinants of health-related states/events in specified populations, and the application of this study to the control of health problems (how often diseases occur in different groups of people and why)
What is exposure and outcome?
Exposure – the variable being tried to associate with a change in health status
Can be a drug/behaviour/demographic characteristic etc.
Outcome – the associated change in health status
Example: drug X (the exposure) and test its association on mortality at five-years (the outcome)
What is primary level intervention?
Primary – preventing disease through control of exposure to risk factors
–> before disease onset
What is secondary level intervention?
Secondary – the application of available measures to detect early departures from health and to introduce appropriate treatment and interventions
–> slows progression
What is tertiary level intervention?
Tertiary – the application of measures to reduce/eliminate long term impairments and disabilities, minimising suffering caused by existing departures from good health and to promote the patients adjustments to their condition
–> enables return to function
What are the four stages of the epidemiologic transition model?
- Pestilence and Famine
- Receding Pandemics
- Degenerative and Man-Made diseases
- Delayed, degenerative diseases, and emerging infections
What does the first stage of the epidemiologic transition model entail?
Pestilence and Famine
- Urbanisation
- Food supply constraints
- High birth rate + mortality
- Low life expectancy at birth
What does the second stage of the epidemiologic transition model entail?
Receding Pandemics
- Agricultural development improves nutrition
- Increased life expectancy
- Water, sanitation, hygiene
- Vaccination
- High birth rate → reduced mortality
What does the third stage of the epidemiologic transition model entail?
Degenerative and Man-Made Diseases
- Lifestyle factors and NCDs predominate
- Environment drives obesity/other risk factors
- Technology →less need for physical labour
- Addiction, violence etc.
What does the fourth stage of the epidemiologic transition model entail?
Delayed Degenerative Diseases and Emerging Infections
- Health tech lowers morbidity but at financial cost
- Emerging zoonotic disease
- Inequalities within and between countries
How do you calculate odds?
= P / (P-1)
Where p = probability of an event
p-1 = the probability of its complement
What is prevalence and how to calculate?
Prevalence - the proportion of individuals in a population who have an attribute at a specific timepoint.
= P/ n
P = number with attribute n = total number of individuals in population
- reflects both occurrence and duration
- doesn’t provide into on new cases
- always specify timepoint
What is cumulative incidence and how to calculate?
Cumulative incidence - the proportion of the population with a new event during a given time period.
= x/y
x= no. of disease-free individuals during a period of interest. y= no. of disease-free individuals at the start of this period.
- don’t include whose who already had the disease
- be explicit about time period
- aka. incidence proportion/risk
What is incidence rate and how to calculate?
= x/T
x = no. of new cases during the follow up period. T = total person-time by disease-free individuals
Person time - time participants spend in the study
- Unit = person/time
- Value 0 = infinity
- Can be used if people enter/leave the study during the study duration
What is direct standardisation?
Gives comparable incidence/prevalence
Allows comparison of like-for-like between populations – normally age or sex
Calculation overview: (won’t be asked to calculate!)
- Use age/sex specific data from two populations
- Calculate crude incidence/prevalence rate for each age/sex grouping
- Apply these rates to a standard population (e.g. the European Standard Population) to find expected rates for each population
- Calculate age/sex-specific standardised incidence/prevalence by dividing each total expectation over each total population
