Abstract
Purpose: :
To systematically review evidence on the association between C-reactive protein (CRP) levels and late age-related macular degeneration (AMD).
Methods: :
Observational studies investigating the association between CRP and AMD were identified from Medline (1950-present), EMB ALL reviews (to February 2009) and abstracts from the Association for Research in Vision and Ophthalmology (ARVO) to 2008. Studies were included if they investigated patients aged 50+ years with late (or early and late combined) AMD. Data were extracted from the included studies using a standard template. A systematic review was performed to provide a quality ranking for each study according to the study design and methods. A meta-analysis was performed using Comprehensive Meta-Analysis Version 2 (Biostat, Englewood, NJ, USA) and random effect models, incorporating sample size information. Meta-analyses were stratified by study sample type, method used to detect AMD, and study design.
Results: :
Of the 43 abstracts identified, 9 studies met the selection criteria. The total sample size from these 9 studies was 11,053 participants aged 49 years to 95 years old. In all 9 studies, AMD was identified from either a detailed fundus examination by ophthalmologists or retinal photographic grading by trained graders. The grading of AMD followed comparable grading protocols across the 9 studies. CRP levels were measured using a high sensitivity assay and assessed either continuously or categorically. Odds ratios reported by these studies were adjusted for age, gender and smoking status. Higher CRP levels were associated with increased likelihood of having late stage AMD (estimated from meta-analysis, OR 1.65, 95% confidence interval (CI), 1.20-2.26). Sub-group meta-analyses showed higher magnitude in the association of high level CRP with AMD found from studies using ophthalmoscopic examination compared to those using photographic grading (OR 4.06, 95% CI 2.12-7.78 versus OR 1.35, 95% CI 1.09-1.68 respectively), or clinic-based samples compared to population-based samples (OR 1.70, 95% CI 1.30-2.21 versus OR 1.17, 95% CI 0.91-1.50 respectively).
Conclusions: :
Higher levels of CRP, compared to lower levels, were found to be associated with a 30% to 100% higher risk of late stage AMD, estimated from 9 clinic- and population-based studies.
Keywords: age-related macular degeneration • inflammation