A set of training materials for professionals working in intervention epidemiology, public health microbiology and infection control and hospital hygiene.
Need help with your investigation or report writing? Ask the Expert. Free advice from the professional community.
You can't make decissions on this page's approval status because you have not the owner or an admin on this page's Group.
Jean Claude Desenclos
Cohort studies measuring incidence rates
The computation of effects with incidence rates is similar to calculation of effects from incidence proportions (risk). The incidence rate of disease in exposed (IRe) and unexposed (IRu) can be computed as follows:
A rate difference can be computed:
The relative effect of the exposure on disease occurrence can be measured by computing the rate ratio minus 1.
The rate ratio is:
Breast cancer cases and person-years of observation for women with tuberculosis repeatedly exposed to multiple x-ray fluoroscopies and unexposed women with tuberculosis
Source: Boice & Monson 
One can express the result by saying that the relative effect is 0.86 which would suggest an 86 % increased rate of breast cancer among exposed. One can also express the results by saying that the rate of breast cancer is 1.86 times higher in the exposed cohort than in the unexposed cohort.
Join the discussion about this article in the forum!
ecdc posted on 10/17/2012 3:17:54 PM:
Populations are more or less dynamic in time and place. The IJE just published the article "Incidence rates in dynamic populations"
Abstract: The purpose of the present article is to explain the calculation of incidence rates in dynamic populations with the use of simple mathematical and statistical concepts. The first part will consider incidence rates in dynamic populations, and how they can best be taught in basic, intermediate and advanced courses. The second part will briefly explain how and why incidence rates are calculated in cohorts.
Ref: Jan P Vandenbroucke and Neil Pearce: Incidence rates in dynamic populations Int. J. Epidemiol. (2012) 41(5): 1472-1479 doi:10.1093/ije/dys142 http://ije.oxfordjournals.org/content/41/5/1472.full.pdf+html
You need to be logged in to post comments.
You can log in here. You can register here if you haven't done so yet.