USING SMOOTHING SPLINE ANOVA TO EXAMINE THE RELATION OF RISK-FACTORS TO THE INCIDENCE AND PROGRESSION OF DIABETIC-RETINOPATHY

Smoothing spline ANOVA (ANalysis Of VAriance) methods provide a flexib le alternative to the standard parametric GLIM (generalized linear mod els) methods for analysing the relationship of predictor variables to outcomes with data from large epidemiologic studies. These methods all ow the visualization of relationships not readily fit by simple GLIM m odels, and provide for the ability to visualize interactions between t he variables. At the same time, they reduce to GLIM models if the data suggest that the added flexibility is unwarranted. Using this method, we investigate risk factors for incidence and progression of diabetic retinopathy in a group of patients with older onset diabetes from the Wisconsin Epidemiological Study of Diabetic Retinopathy. We carry out four analyses to illustrate various properties of this class of metho ds. Some of the results confirm previous findings with use of standard methods, while others allow the visualization of more complex relatio nships not evident from the application of parametric methods. (C) 199 7 by John Wiley & Sons, Ltd.