Assignment: For a specific exposure-outcome combination of interest to you, specify which lifecourse model is likely most appropriate and why you think this is the case. Describe the regression models you could use to test your hypothesis. Are there any possible data sets in which this test could be conducted, and if so, what concerns would you have about interpreting your proposed test of the lifecourse model?
Exposure: adverse/traumatic event (categorical variable) measured at different time points across the life course
Outcome: development of opioid use disorder (binary variable)
The accumulation of risk model is the most compelling model to answer the question: do adverse events across the life course increase the risk of developing opioid use disorder (OUD)? Under this model, we would expect that individuals with more adverse/traumatic events will have a higher likelihood of developing OUD than individuals with a lower total number of adverse/traumatic events over the life course. This model functions irrespective of the timing of adverse events, which is distinct from the critical or sensitive models which focus on the timing of adverse events, rather the accumulation of events. I’m not sure if the outcome is more influenced by the linearity or amount of the exposure. According to Mishra et al, we can assess each of these according to two different models. If the outcome depends on the amount of exposure, then Y011 < Y001 and Y111 < Y011 (where Y is exposure and 001-111 represent the different exposure options at the three different time points. For this example there are three time points). If, however, the outcome depends on the linearity of the exposure then we can create a lifetime adverse events score and assume that every trajectory can be represented by the total number of exposed periods. For every additional adverse event, the change in mean OUD is assumed to be:
^acc = (Y111 – Y000) / 3 = Y111 – Y011 = Y111 – Y101
If we assume a direct and cumulative causal effect of adverse event on OUD then ^acc is the causal parameter of interest. The linear regression would be:
E(Y) = α + β ∑ Sj
I don’t know of any datasets that routinely track the exposure, adverse events. The outcome can be tracked by medical chart and can be extracted by a manual chart review. There are some events that would be recorded in medical charts that could be used as proxies for adverse/traumatic event (e.g. sexual assault, traumatic injury) but that would only capture a small percentage of potential adverse events in someone’s life course.
If there was an irreversible physiological or biological change based on fetal exposure to opioids in the presence of maternal opioid use during pregnancy, the the critical period model would be ideal for assessing the development of OUD based on this critical event.