Measuring and Describing Disease part 2 Flashcards
List the 6 types studies in the hierarchy of evidence from strongest to weakest.
Systematic reviews and meta-analysis
Randomised controlled trials
Cohort studies
Case-control studies
Case series, Case report
Editorials, expert opinion

What are the two main research methods?
Qualitative
Quantitative
What are the two main study designs?
Observational research
Interventional research
What are the two main types of epidemiological approaches?
Descriptive epidemiology
Analytical epidemiology
What is the main purpose of qualitative research?
Explores underlying ideas and themes to inform possible research questions and help in establishing a future hypotheses
How are findings and outputs expressed in qualitative research?
Findings described in words
How does the sample size differ in qualitative research versus quantitative?
Sample size of participants is smaller but goes into substantial detail
What are the 3 main causes of morbidity/mortality? List them from most common to least common in the UK population
Non-communicable diseases (e.g. CVD, Cancers)
Communicable diseases (e.g. malaria, infections)
Injuries (e.g. traffic accidents, violence)
What are the 4 measures of frequency?
Odds
Prevelance
Cumulative incidence
Incidence rate
Define odds
The ratio between the number of people who have the disease to the number of people who dont have the disease
N.B. The ratio of the probability (P) of an event to the probability of its complement (1-P).

In the context of odds, what is the output number above which it becomes more likely an event takes place than does not take place?
1.0
Because if half the population has the outcome the calculation will be 1 so any number higher than half the number will produce a value higher than 1
(e.g. 6 people sleep 6 people awake = 6/6 =1. 7 people sleep 5 people awake = 7/5 =>1)
Define prevalence
Proportion of individuals in a population who have the disease or attribute of interest at a specific point in time
N.B. proportion not ratio
How is prevelance calculated?
Number of people with disease/ Total population
N.B. The measure can be a percentage or in decimals and you have to specify the timepoint in which this value was calculated (e.g. 20% of students have sleeping disease at 10am)
What is a flaw of prevalence?
Prevalence provides no information on new cases of a disease (is only a snapshot).
Therefore not a good measure when trying to establish frequency of short duration diseases
Define cumulative incidence
Proportion of the population with a new event during a given period of time.
N.B. Useful when wanting to see how the frequency of cases change over given periods of time
How is cumulative frequency calculated?
Number of new cases in period of interest/ Number of disease free individuals at start of time period
N.B. Remember to state this period of time (e.g. 50% cumulative incidence of sleeping disease over a 5 hour time period)
N.B. Do not include people that are already ill at start of time period as part of the bottom denomiator
What does a cumulative interest of 0% indicate?
No new incidences have occured within this time period
What does a cumulative incidence of 100% indicate?
All individuals developed the disease during this time period
What are 2 alternative names for cumulative incidence?
Risk
Incidence proportion
What is a weakness of cumulative incidence?
Cumulative incidence can look at the proportion of disease but it cannot tell us when a disease occurs within time period (cannot calculate the rate of new cases of disease)
Can cumulative incidence be calculated in studies without a follow up?
No as they would not be able to see how many people in the observed sample developed the disease if they arent seen again
N.B. another weakness
What are the 2 main implications of follow up studies?
Some people in study population may drop out/die before follow up
Some people may enter the study population before follow up
What measures can address the problems associated with cumulative incidence?
Incidence rate
Define person-time
Measures time participants spend in the study.
(person hours stop at moment they develop disease or leave study)
(e.g. person enters a 9am lecture at 10am and develops sleeping disease at 1pm means they contributed 3 person hours)
N.B. bottom person in grey doesnt contribute to anything as they already had disease during start of study period



