Association between exposure to Chlamydia pneumoniae infection and AMD progression: Cardiovascular Health and Age–Related Maculopathy (CHARM) Study

Abstract

Abstract: : Purpose: To examine the association between exposure to Chlamydia pneumoniae infection and 7–year AMD progression. Methods: Subjects with early AMD at baseline (1992–95) were re–examined (2001–02) and interviewed. Standardised examination included blood collection and macular photography. Progression of AMD was defined as a stepped increase in grading in either eye according to the International Grading of AMD. Serological tests (ELISA) were performed to measure exposure to C. pneumoniae infection (using elementary bodies (EBs) from C. pneumoniae AR39). Titers were expressed as optical density (OD) values. Data were analyzed using the t–test, Chi–square test, Mann–Whitney test and logistic regression analysis. Results: Of 254 subjects aged 51–89 years (Mean 74 ± 7SD,) 135 (53%) were female, 117 (46%) former or current smokers and 12 (4.7%) had family history of AMD. In 83 (33%) cases AMD progressed. Serological data were available for 246 subjects. Progression was strongly associated with smoking and age (p≤0.010 and p≤0.003, respectively) and weakly with family history of AMD (p≤0.112 ). In 16/82(20%) cases AMD progressed in the lowest, in 30/82(37%) in the middle and in 36/82(44%) in the upper tertile of antibody titer. After controlling for age and smoking, the increase in antibody titers to C. pneumoniae was associated with AMD progression. Subjects in the two upper tertiles of antibody titer were significantly more likely to have AMD progression than those in the lowest tertile (OR=2.09, 95%CL=1.01, 4.32, for the 2nd tertile and OR=2.97, 95%CL=1.45, 6.08, for the 3rd tertile). This association was not affected by the history of high blood pressure, stroke and/or heart disease. Conclusion: Sero–reactivity to C. pneumoniae elementary bodies was independently associated with ARM progression. It is plausible that C. pneumoniae infection may be an additional risk factor for AMD progression, and this could suggest a possible treatment strategy for some individuals with the disease.

Keywords: age–related macular degeneration • clinical (human) or epidemiologic studies: risk factor assessment