cohort study Flashcards
true or false:
- The term “natural history” refers to how a disease evolves over time and to the factors that shape its evolution
- What the physician sees in his clinic is just an episode of the natural history
true
cohort study investigates — of the disease and the 3 components of this study is:
- natural history
- 3 components are:
1-follow a defined group of participants
2-over a period of time
3-and record the incidence of events of interest
2 main types of cohort studies:
1- —-: Follow up of population groups to document incidence of diseases or disorders and their risk factors
- these tells us how the disease —- in —- people
2- —- : Follow up of patient groups to document natural history and prognosis of a disease or disorder
- these tell us about the —- and the — of the disease
- population cohort
- develops
- healthy ppl
- clinical cohorts
- natural history
- prognosis
population cohort studies:
- provide info on the — of health problems
- General population studies (rare) often take the population of a defined —-
examples:
-Birth cohort studies recruit all children born in a defined period
-Studies may recruit participants in an age range of interest (e.g. persons over 65)
-Occupational cohorts (workers in specific industries are followed up to look for occupational hazards)
incidince
geographical regions
how are the population cohort conducted :
1- identify population group of —- :
-Defined as not already having the —- or — of interest
Can be —- found (e.g. medical charts)
2- measure charactericts at —-:
- classifying into — depending on — status of risk factors ( these risk factors can be genetic environmental or behavioural )
3- —- over time to assess defined endpoint to determine —-
healthy individuals
disease or disorder
retrospectively
at baseline
groups
exposure
follow up
incidence rates
- Not all participants may have been followed up until they experience the —
- Clinical cohort studies usually recruit patients on a —
- Consequently, there is a different length of follow-up on each participant which is termed as —-
endpoint of interest
rolling basis
survival time
- Special statistical methods (survival analysis) are required to account for —-
- kaplan meier curve show whether or to — happen or how — it takes for them to happen
- at the start the time will = to — for all patients and 100% don’t have — so the proportion surviving is —
- steps represents —- occurring
- Survival proportions (probabilities) incorporate censoring into their calculations
variable follow up
event ( outcome )
how long
zero
outcomes
1
outcomes
( check slide 17-23 important for example plsss)
- Cohort studies provide strong evidence that the association between a — and — is —
- this is bc the risk factors are measured — the disease occur
- Nonetheless, the people with and without the risk factor may not be comparable
- —- can be used to adjust the comparison for known differences between them, but other, unmeasured differences may act to distort the relationship between risk factor and disease that we observe in the data
risk factor and outcome
is causal
before
statistical measure
-clinical cohort studies study — and —
- the cohort is a —- which defined — or —
- they are followed from a — in the natural history of the disease or condition for example: from time of diagnosis, or date of discharge
- The study records incidence of —- and— which affect the incidence for example: —-
natural history and prognosis
group of participants
diagnosis or condition
defined point
clinical endpoint
factors
examples: . mortality and morbidity, readmission, disease progression
( check slide 26-32pls)
strengths of cohort studies:
- cohort often study —– which is impritsnt to justify the — of follow up
- they record — which is important info for health care service —
- —- is the the rate of occurrence of new cases per unit time per unit population
- it indicates the – of contracting a disease ( communicable or non )
- useful for population —- as : . emerging or resurging disease
- indicator of the scope for —
multiple different endpoints
high cost
record incidence
planning
incidence ( example: Incidence of cancer is 800 new cases per 100,000 per year in Ireland or, equivalently, 0.8% chance per year for any person)
risk
population surveillance
prevention
strengths of cohort studies ( continued )
- Less biased information on risk factors because the risk factor is measured — the disease occurs
- Unlike case-control studies and “Retrospective” cohort studies, which ascertain exposure retrospectively
- Time-order with regard to risk factor is —: less susceptible to biases associated with cross-sectional or case-control studies
- The results are — to —- to the population aka —-
before
clear
easier
generalise
external validity
weakness of cohort studies:
- collecting data requires —
- —- of study ( specific time-frame of the study )
- Even for common diseases, a lot of —- needed to detect a worthwhile number of cases
- may require —-
- —- ,—– , —– are issues
- —- to conduct
- Impractical for diseases with a —- and —
follow ups
long duration
follow ups
large sample size
Non-response, migration, loss-to-follow-up and selection biases are issues
expensive
long pre-clinical phase (latency period) which is the phase before the first clinical manifestation and impractical for rare disease
summary :
1- cohort studies :
- followed a — of participants
- over a —-
- record — of events of interest
2- —- studies study incidence of disease to look for risk factors
3- —– studies examine the natural history and prognosis of a disease, looking for factors that affect —- and possible —- by which they work
defined group
period of time
incidence
population cohort
clinical cohort
prognosis
mechanisms
summary :
all cohort studies :
- measure —- then —- and record —- of events
- they measure the effect of risk factors by comparing —- which is the relative risk
- When looking for causes of diseases, they do not provide as —– as —-
risk factors
follow up
incidence
incidence
strong evidence as intervention studies ( In many cases intervention studies are not possible, so they provide the strongest actual evidence)
