Flashcards in Sem 2 Pop Sci Deck (42)
Describe a population graph, and the four main types of population graphs. (10)
They have % population on the x axis, against age, with one line for male and one line for female.
Rapidly expanding - curved lines, wide at the bottom, narrow at the top.
Expanding - straight diagonal lines to a point at the top.
Stationary - vertical lines which slowly curve off at the top.
Contracting - narrow at the bottom, to vertical lines, curves in at the top.
Define public health (3)
The art and science of preventing disease, prolonging life, and promoting health through the organised efforts of society.
Describe the three types of prevention used in public health. Give two examples of each. (9)
Primary - prevent the onset of disease by reducing exposure to risk factors - immunisations, reducing smoking.
Secondary - to detect and treat a disease at an early stage to prevent further harm - cervical cancer screening, monitoring bp.
Tertiary - harm limitation of an already established disease - thiamine for alcoholism, steroids in asthma.
Describe the three domains of public health. Give an example for each. (6)
Health improvement - sexual health, weight, smoking, mental health
Health protection - screening, immunisations, emergency responses.
Public health in healthcare - prioritisation, research, assessment
Define epidemiology. (1)
Study of how exposure affects disease.
Explain the difference between chance and systematic errors. (2)
Chance - due to individual differences, random.
Systematic - bias, lowers accuracy.
Explain why a study needs both internal and external validity. (4)
Internal validity - means the comparison groups are actually comparable.
External validity - means the results are generalisable because the samples are representative of the whole population.
Describe these error types:
Recall - error common when recollecting the past.
Observer - error due to pre-conceived expectations.
Measurement - due to equipment and interpretation.
Define prevalence. (2)
Proportion of people who have a disease at a point in time - diseased / whole population.
Define incidence. (2)
Number of new cases of a disease within a certain time frame - number of new cases / population at risk.
Describe a case control study design. Give an example. (4)
Find current cases and controls, look for past exposure.
Current asthma and currently no asthma, look for previous exposure to a mouldy house.
Describe how from a case control study you would work out the odds of an exposure having an effect or not. (2)
Describe how you would work out the odds ratio. (3)
Exposed = cases (a) + controls (b)
Unexposed = cases (c) + controls (d)
Odds of exposure having an effect = a / c
Odds of exposure not having an effect = b / d
Odds ratio = (a / c) / (b / d)
= ad / cb
Give two issues with case control study designs. (2)
Describe a cohort study design. (2)
Give an example. (2)
Describe the two types of cohort design. (2)
Find unexposed and unexposed people, look for future development of the disease.
Mouldy house vs not mouldy house now, look for asthma in the future.
Can be prospective (exposed now, future outcome), or retrospective (exposed past, outcome now).
Describe how you would work out the incidence rate of the exposed population in a cohort study. (2)
IR of exposed = number that developed the outcome in the exposed group / person years at risk.
Describe how you would work out the incidence rate ratio in a cohort study. Explain the purpose of this. (3)
IRR = IR of exposed / IR of unexposed.
Shows how much more likely you are to develop the disease if you were exposed.
Describe 4 issues with a cohort study design. (4)
Loss to follow up
Describe a cross sectional study design. Give an example. (2)
Find the number of cases right now in a snapshot form.
2011 = 250,000 asthma cases
2014 = 350,000 asthma cases
Describe how to work out the prevalence of a disease. What is another name for the prevalence? (3)
Prevalence = number of people with the disease / total population = absolute risk.
Describe the way you work out incidence rate in a cross sectional study. (2)
Number of new cases / sum of person years at risk.
Give 3 issues with cross sectional studies. (3)
Describe an ecological study design. Give an example. (3)
Look at the whole population, separate by characteristic, look at cases in each group.
Men with asthma vs women with asthma.
Give 4 issues with ecological studies. (4)
Characteristics could be unclear
Lack of generalisability (dep on sample size)
Explain the differences between rate and ratio. (2)
Rate = number of events per population per time.
Ratio = comparison of rates/odds/anything .
Explain the difference between ratio and proportion. (2)
Ratio = one number divided by another.
Proportion = fraction where the top part has to be included in the bottom part.
Explain the difference between ratio and difference. (2)
Ratio = one number divided by the other
Difference = one number subtract another.
Explain the difference between confounding and bias. (4)
Confounding = a situation in which a measure of the effect is distorted by association of the intervention with other influencing factors. Confounder must link to both risk (eg exposure) and outcome.
Bias = a systematic distortion in allocation / measurement etc.
Explain the difference between random selection and random allocation. (4)
Selection = recruitment into a clinical trial, affecting generalisability (external validity)
Allocation = within the groups in the study (internal validity).
Explain the differences between a screening test and a diagnostic test. (3)
A screening test gives you a risk (ie if you screen positive you are have a high change of having the disease - not 100%)
A diagnostic test tells you whether you have the disease or not (100%).