Analytic Approaches in Epidemiology



QUESTION 1: [25 marks]

A prospective cohort study of psychiatric outpatients with a history of suicidal ideation was conducted, investigating the effect of alcohol consumption and incidence of attempted suicide over a follow-up period of 24 months. The data at the end of the follow-up period for males and females are given below.
MalesAlcohol consumption Cases ParticipantsLight 5 250Heavy 23 375
FemalesAlcohol consumption Cases ParticipantsLight 25 250Heavy 52 167
Assume no loss to follow-up and that all participants were followed over the follow-up period.
Discuss statistical interaction and confounding by sex for the following effect measures
-Risk difference-Risk ratio-Odds ratio
QUESTION 2 [10 marks]
Propose a causal diagram of the relationship between alcohol consumption and attempted suicide, based on the variables provided above. Provide a narrative description (1 paragraph only) of the causal diagram incorporating findings from your analysis in Question 1.
QUESTION 3 [10 marks]
Name 5 advantages of Propensity Score Methods.
QUESTION 4 [30 marks]
The data in the table below are taken from the National Mental Health Survey, a large, nationally representative cross-sectional prevalence survey estimating 12-month prevalence of a range of mental health, service use, and disability factors in addition to socio-demographic variables. Similar questions regarding alcohol consumption and suicidal behaviour were asked of participants. An extract of the data are given below, stratified by males and females.
MalesAlcohol consumption Cases ParticipantsLight 31 2885Heavy 7 1109
FemalesAlcohol consumption Cases ParticipantsLight 26 4387Heavy 4 542
Discuss statistical interaction and confounding by sex for the following effect measures:
-Risk difference-Risk ratio-Odds ratio
In your discussion compare your estimates with those from Question 1. Comment on similarities or differences on effect estimates, and likely reasons for these similarities or differences (limit of 2 pages).

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