Risk factors for conversion to advanced forms of AMD

Abstract

Purpose : Age-related macular degeneration (AMD) is a significant public health problem that is likely to become more prevalent as the US population continues to age. Understanding risk factors for conversion from the earlier forms of AMD to advanced can identify persons at higher risk.

Methods : Intermediate AMD patients enrolled in the University of Colorado AMD Registry from 2014 -2023. Conversion to advanced AMD (either neovascular (NV) or geographic atrophy (GA)) in these patients was determined using multimodal images. Competing risks analyses were performed to compare rates of conversion between NV and GA and to identify risk factors associated with either form of advanced AMD. Random survival forests were used to perform variable selection and identify potential interactions on 73 demographic and clinical risk factors, including the visual function questionnaire (VFQ), collected at study enrollment.

Results : Of the 231 intermediate AMD patients that were followed, 87 (38%) converted to advanced AMD with 39 converting to GA and 48 to NV. The median (range) time to conversion was 33 (2 – 84) months and the follow-up time for non-converters was 45 (1.4 – 101) months. At 2 years, the conversion rate was higher for NV (10.4%) compared to GA (4.3%), these rates were not different at 3 years. Different risk factors were identified for time to conversion to GA or to NV, no history of infectious disease was the only variable associated with both outcomes (Figure). Current use of diuretics was the top ranked factor associated with NV, this variable remained an independent risk factor after accounting for history of cardiac disease and presence of abnormal lipids. For GA, the top ranked factors also included age, general vision VFQ assessment and presence of reticular pseudo drusen (RPD). Diuretics and RPD would not have been identified if evaluating overall conversion.

Conclusions : The conversion rates and risk factors identified in our cohort are similar to those observed in previous studies. The application of competing risks analysis suggests different risk factors exist for conversion to GA and to NV.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.

 

Variable importance measures (VIMP) from the random survival forest assessing time to conversion to either GA (y-axis) or NV (x-axis). Higher VIMP values indicate important risk factors. VIMP for the composite outcome is indicated using the color scale, variables in blue and black would have not been identified using the composite outcome.