Public Health And Epidemiology

Question 1

Definition of epidemiology

Answer 1

• study of the distribution and determinants of the frequency of health-related outcomes in specified populations
• using effect measures look at the association

Question 2

Definition of prevalence and incidence risk and rate

Answer 2

• prevalence: number of existing cases of a disease / population of interest
• incidence risk: number of new cases in a given time period / total population at risk
• incidence rate: number of new cases in a given time period / (total person-time at risk)

Question 3

Nutritional issues in the UK population

Answer 3

• <0.1% of the UK eats to the EatWell guide recommendations
• 60% of women and 70% of men are overweight or obese
• vitamin D deficiencies are seen across all age categories
• sugar intake is 2x what is recommended
• fibre is 15-21g per day (rather than 30g)
• low folate in 28% of girls and 7% of adults
• iron deficiency anaemia in 9% of girls and 5% of adult women

Question 4

Relative measures of effect: relative risk and odds ratio

Answer 4

• relative risk is used when the risk has a clear time point. RR=R1 (incidence in exposed/total exposed)/ R0 (incidence in unexposed/total unexposed)
• odds ratio is used when no clear time-point for exposure i.e questionnaire. OR=O1 (odds exposed/those without disease and exposed)/ O2 (odds unexposed/those without disease and unexposed)

Question 5

Alternative explanations for associations: chance, bias, confounding

Answer 5

• bias: selection bias (those in study not representative), reporting bias (recorded data not accurate). This is systematic distortion of the data
• chance: random error/ noise
• confounding: 3rd variable with is correlated with both exposure and outcome but doesnt lie in association pathway

Question 6

Study designs and pros/cons

Answer 6

• interventional: RCT
  Observational examples:
• ecological studies: whole countries. Pros: cheap, hypothesis generation. Cons: extrapolation can lead to wrong conclusions
• cross-sectional studies: on same person measuring effect and outcome. Pros: quick, cheap. Cons: temporality unclear
• case-control: start at disease assessment and go back in time. Pros: good for rare diseases and quick. Cons: recall bias, and temporality is a problem
• cohort studies: start with healthy people and see how they change with time. Pros: temporality is clear. Cons: time consuming and expensive to follow up