studies

Question 1

the main features of a cross sectional study

Answer 1

useful to allocate resources and plan prevention
provide clues leading to hypothesis - tested in analytical studies, dont find answer
information is collected at 1 point in time
see how people are wth and without exposure and disease at the same point in time
can’t distinguish whether exposure preceded disease

Question 2

examples of cross sectional surveys

Answer 2

Health survey for England - core and special topics eg focus on diabetes
census - count people, housing - overcrowding, health question and other health indicators, unemployment, ethnicity, age, overcrowding
vital registration - needs updating, birth marriage death
mortality - office of national statistics - code cause of death, public health mortality files, data extracts

Question 3

features of a case control study

Answer 3

commonly used in epi
suitable for studying what might cause rare disease
retrospective - cases and controls divided and then you compare past exposure and other factors and compare proportions of people exposed in cases and controls
controls are free of the disease at the time the cases were identified - representative of the cases if they also had the disease
source of controls: general population, neighbourhood, friends hospital/clinic based
take representative sample of the case

Question 4

advantages of case control studies

Answer 4

good for rare diseases
quick and cost efficient
investigate many exposures simultaneously

Question 5

disadvantages of case control studies

Answer 5

selection bias 
recall bias - cases likely to exaggerate exposure
don't know if exposure was first 
poor for rare exposures 
can't calculate incidence rates directly

Question 6

Describe a cohort study

Answer 6

cohort - group of people with something in common
outcome free population - some exposed some not - cases eventually arise
calculate relative risk: no exposed with/without
no not exposed with/without
ratio of above exposed/not exposed

Question 7

Advantages of a cohort study

Answer 7

look at multiple outcomes
follow natural history of disease 
risks to rare exposures
incidence calculated 
minimise bias by estimating exposure

Question 8

disadvantages of a cohort study

Answer 8

inefficient for rare diseases
expensive and time consuming
loss to follow up introduce bias
healthy worker/volunteer effect may affect generalisablity

Question 9

features of descriptive studies

Answer 9

describe relation of factors/disease to person (e.g. age, sex, race, marital status, occupation, lifestyle), place (e.g. variation between and within countries/units – CQC does this), time (variation over time and season)