A genetic variation, combined with inflammatory factors and smoking, significantly increases the risk of developing age-related macular degeneration, according to a study.
Recent case-control studies have shown an association between AMD and the complement factor H (CFH) gene, a regulator of the complement pathway, the study indicated. Dominiek D.G. Despriet, MD, of the Erasmus Medical Center in Rotterdam, the Netherlands, and colleagues hypothesized that this regulator gene’s effect may be hazardous in patients who have the complement cascade activated.
Researchers examined the association between the CFH gene and AMD in a prospective, population-based study involving 5,681 patients who were at least 55 years old. All patients had the CFH Y402H polymorphism. They also investigated the modifying effects of smoking, serum inflammatory markers and genetic variation of C-reactive protein (CRP).
The researchers found that 36.2% of alleles had the CFH Y402H gene mutation (4,116 of 11,362 alleles). At baseline, 2,062 patients (36.3%) had any type of AMD, including 78 patients (1.4%) with stage 4 AMD or later. At a mean follow-up of 8 years, 1,649 of 4,642 patients (35.5%) had progressed to a higher AMD stage, including 93 patients (5.6%) who developed late AMD, according to the study.
Homozygous patients were at particularly increased risk, having a 48.3% cumulative risk for developing late AMD by age 95. Comparatively, heterozygote patients had a 42.6% risk, while patients without the CFH Y402H mutation had a 21.9%.
Smoking further increased the late AMD risk 34-fold, elevated serum CRP levels increased the risk 28-fold and elevated sedimentation rates increased the risk 20-fold, according to the release.
“Genetic predisposition to a malfunctioning CFH can only be of importance when the complement system is switched on,” the authors wrote. “This is demonstrated by the significant interaction between chronic as well as acute inflammation and CFH Y402H.”
The study is published in the July 19 issue of the Journal of the American Medical Association.