Some risk factors exert a risk on a per event basis. The total cumulative risk for that risk factor depends on the number of events that occur. This information can be used to determine how many events must occur to achieve a certain risk or hazard ratio.


cumulative risk for the factor =

= (relative risk per event) ^ (number of events)


To achieve a certain threshold for a cumulative risk:


number of events =

= LN(target cumulative ratio) / LN(relative risk per event)


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