Estimates of incidence rates with longitudinal claims data

Objective: To estimate incidence rates of the 3 major chronic eye diseases - diabetic retinopathy (DR), glaucoma, and age-related macular degeneration (ARMD) - by using longitudinal claims data from Medicare. Methods: Longitudinal cases were ascertained by using a national probability sample of Medicare beneficiaries aged 65 years and older in 1991 who initially had none of the eye diseases documented. After adjusting for death and enrollment in a health maintenance organization, claims filed by optometrists or ophthalmologists with an International Classification of Diseases, Ninth Revision, Clinical Modification code for all forms of DR, glaucoma, and ARMD were used to indicate diagnosis. Results: Annual incidence rates for the 3 conditions after the first year of observation ranged from 14.3% to 17.7% (higher earlier) across an 8-year longitudinal follow-up. Incidence rates among those with diabetes mellitus for any form of DR varied between 3.8% and 6.5%, while those for glaucoma varied between 4.6% and 7.8% and those for ARMD varied between 7.5% and 9.3%. Conclusions: Longitudinal claims data after the first year provide relatively stable estimates of incidence rates on an annual basis. These estimates are comparable with those of the few population-based studies available.