%0 Journal Article
%T A new approach of nonparametric estimation of incidence and lifetime risk based on birth rates and incident events
%A Henrik St£¿vring
%A Mei-Cheng Wang
%J BMC Medical Research Methodology
%D 2007
%I BioMed Central
%R 10.1186/1471-2288-7-53
%X We compare two different approaches for obtaining nonparametric estimates of age-specific incidence and lifetime risk with emphasis on required assumptions. The first and novel approach only considers incident cases occurring within a fixed time window¨Cwe have termed this cohort-of-cases data¨Cwhich is linked explicitly to the birth process in the past. The second approach is the usual Nelson-Aalen estimate which requires knowledge on observed time at risk for the entire cohort and their incident events. Both approaches are used on data on anti-diabetic medications obtained from Odense Pharmacoepidemiological Database, which covers a population of approximately 470,000 over the period 1993¨C2003. For both methods we investigate if and how incidence rates can be projected.Both the new and standard method yield similar sigmoidal shaped estimates of the cumulative distribution function of age-specific incidence. The Nelson-Aalen estimator gives somewhat higher estimates of lifetime risk (15.65% (15.14%; 16.16%) for females, and 17.91% (17.38%; 18.44%) for males) than the estimate based on cohort-of-cases data (13.77% (13.74%; 13.81%) for females, 15.61% (15.58%; 15.65%) for males). Accordingly the projected incidence rates are higher based on the Nelson-Aalen estimate¨Calso too high when compared to observed rates. In contrast, the cohort-of-cases approach gives projections that fit observed rates better.The developed methodology for analysis of cohort-of-cases data has potential to become a cost-effective alternative to a traditional survey based study of incidence. To allow more general use of the methodology, more research is needed on how to relax stationarity assumptions.Diabetes is a severe disease, which is becoming increasingly prevalent in countries throughout the world [1-6]. From a public health perspective it is vital to get good estimates of the present and future burden of diabetes. One measure of primary interest is diabetes incidence, both with respect to
%U http://www.biomedcentral.com/1471-2288/7/53