Hey @danieltds, see this example from Boston University’s SPH: The Population Attributable Fraction
Population attributable fraction, also known as population attributable risk percent (PAR%), answers the question: What proportion of the disease risk in the total population is due to a specific exposure? It answers a causal question.
Here is a screenshot of a few slides from one of my intro EPI lectures, where we are starting with information from a cohort study. In a cohort study, we can calculate risk (incidence) of an outcome (e.g PD) in an exposed and unexposed group (e.g. smokers vs non-smokers) - which we can leverage to estimate risk in the general population (see the first few slides). If you have the risk of disease in the general population then you can start at slide 73 (where AR = attributable risk which is: risk in exposed - risk in unexposed):
Happy to chat more!