What does incidence rate ratio mean in this specific case?
"Poisson regression models were used to estimate the suicide incidence rates and incidence rate ratios (IRRs) along with their 95% CIs within each targeted age group."
The tables give the IRRs as numbers like 1.005 and 1.007, but I don't understand what the numerator and denominator are supposed to be.
Study name - "Association Between the Release of Netflix’s 13 Reasons Why and Suicide Rates in the United States: An Interrupted Time Series Analysis".
^ pasting this into Google should immediately show you a PDF link
In the context of the specific study you mentioned, the incidence rate ratio (IRR) is a measure used in Poisson regression models to compare the incidence rates of suicide within different age groups. It quantifies the relative change in the incidence rate of suicide between two groups of interest.
To better understand how the IRR is calculated, it is necessary to have the specific equation used in the Poisson regression model. Unfortunately, since I don't have access to the study or the exact equation used, I can't provide the specific details. However, I can explain the general concept of calculating the IRR in a Poisson regression model.
In a Poisson regression model, the dependent variable is typically the count of events (in this case, the number of suicides) occurring within a specific unit of time or space. The independent variables can be factors such as age groups or any other variable of interest that might be related to the incidence of the event.
The IRR is calculated by comparing the predicted incidence rate (based on the Poisson regression model) for one group, such as a specific age group, to a reference group. The reference group is usually chosen as the baseline or comparison group. The IRR represents the ratio of the predicted incidence rate in the group of interest to the predicted incidence rate in the reference group.
For example, if the incidence rate ratio (IRR) is 1.005 for a certain age group compared to the reference group, it indicates that the predicted incidence rate for the age group is 1.005 times higher (or 0.5% higher) than the predicted incidence rate for the reference group.
Unfortunately, without specific details about the study or access to the PDF, I cannot provide a more precise explanation of the numerator and denominator used in the calculation of the IRR. To gain a deeper understanding of the study and the specific calculations used, I recommend accessing the PDF link you provided and examining the methodology and results sections of the research paper.