Using splines to analyse latency in the Colorado Plateau uranium miners cohort.

Abstract

BACKGROUND Different approaches have been proposed to investigate latency in epidemiologic studies where detailed exposure histories are available. METHODS We demonstrate the application of a flexible, yet parsimonious, spline function model to investigate latency patterns for radon progeny exposure and lung cancer in the Colorado Plateau uranium miners cohort. The model extends a previously proposed bilinear model. RESULTS The excess relative risk (ERR) reached a maximum of 0.6 per 100 working level months, for exposures received 14 years previously. The ERR then declined, and was estimated to approach zero for exposures received 35 years and more in the past. The point-wise 95% confidence intervals supported ERRs > 0 for the period 9-32 years before the event. The estimated latency curve was homogeneous across categories of attained age, duration of exposure, rate of exposure, and smoking. CONCLUSIONS The proposed spline model is a flexible tool for latency analyses, and extends previously used methods.