Serum Cystatin C Level, Kidney Disease Markers, and Incidence of Age-Related Macular Degeneration

The Beaver Dam Eye Study

Ronald Klein, MD, MPH; Michael D. Knudtson, MS; Kristine E. Lee, MS; Barbara E. K. Klein, MD, MPH

Arch Ophthalmol. 2009;127(2):193-199.

Objective
To examine the associations of the serum cystatin C level and chronic kidney disease with the incidence of age-related macular degeneration (AMD) over 15 years.

Methods
In this population-based cohort study of 4926 individuals aged 43 to 86 years at baseline, 3779 participated in 1 or more follow-up examinations. Age-related macular degeneration was determined by grading photographs of the macula. Individuals were defined as having mild or moderate to severe chronic kidney disease based on a value of more than 45 mL/min/1.73 m2 to 60 mL/min/1.73 m2 or less and 45 mL/min/1.73 m2 or less, respectively, according to the Modification of Diet in Renal Disease Study equation.

Results
While controlling for age and other risk factors, the level of serum cystatin C at baseline was associated with the incidence of early AMD (odds ratio per log standard deviation [95% confidence interval], 1.16 [1.01-1.35]) and exudative AMD (1.42 [1.03-1.96]) but not geographic atrophy (0.89 [0.56-1.41]) or progression of AMD (1.02 [0.88-1.18]). Mild chronic kidney disease was associated with the 15-year cumulative incidence of early AMD (odds ratio per log standard deviation, 1.36 [95% confidence interval, 1.00-1.86]) but not the incidence of other AMD end points.

Conclusion
There is a relationship between the level of serum cystatin C and chronic kidney disease with the incidence of AMD. The underlying biological processes remain to be determined.

Author Affiliations: Department of Ophthalmology and Visual Sciences, University of Wisconsin School of Medicine and Public Health, Madison.