Update of the NIOSH life table analysis system: A person-years analysis program for the windows computing environment†

Background Person-years analysis is a fundamental tool of occupational epidemiology. A life table analysis system (LTAS), previously developed by the National Institute for Occupational Safety and Health, was limited by its platform and analysis and reporting capabilities. We describe the updating of LTAS for the Windows operating system (LTAS.NET) with improved properties. Software Development Process A group of epidemiologists, programmers, and statisticians developed software, platform, and computing requirements. Statistical methods include the use of (indirectly) standardized mortality ratios, (directly) standardized rate ratios, confidence intervals, and P values based on the normal approximation and exact Poisson methods, and a trend estimator for linear exposure–response associations. Software Features We show examples using LTAS.NET to stratify and analyze multiple fixed and time-dependent variables. Data import, stratification, and reporting options are highly flexible. Users may export stratified data for Poisson regression modeling. Conclusions LTAS.NET incorporates improvements that will facilitate more complex person-years analysis of occupational cohort data. Am. J. Ind. Med. 54:915–924, 2011. © 2011 Wiley Periodicals, Inc.