Abstract
Purpose: :
To examine the relationship between residing in urban or rural areas to risk of developing cortical, nuclear or posterior subcapsular cataract (PSC). We hypothesized that risk of cataract would be higher in rural areas due to potential environmental exposures, such as agricultural field runoff, well water contaminants, and dietary and lifestyle factors.
Methods: :
A cohort of residents within the ZIP code of the city of Beaver Dam, WI and its surrounding area were identified through private census in 1987-88. A baseline examination took place in 1988-90 and follow-up examinations were performed every five years through 2003. Address reported at baseline was used to categorize participants into urban (in city of Beaver Dam, not in edge), edge (¼ mile buffer zone on either side of city boundary), or rural (outside of edge, within ZIP code boundary) categories. Slit lamp and retroillumination film photographs were used to identify presence of cataract. Incidence from baseline was calculated, and generalized estimating equations were used to account for correlation between eyes.
Results: :
Of the 4926 persons seen at baseline, 84 lived outside of the Beaver Dam ZIP code boundary, 3372 were classified as urban, 846 as edge, and 624 as rural. Urban residents had a higher cumulative incidence for all types of cataract when compared to rural residents, accounting for competing risk of death. The odds for cataract incidence for rural residents, as compared to urban was 0.93 (p=0.54) for cortical, 0.86 (p=0.16) for nuclear, and 0.71 (p=0.08) for PSC, adjusting for age and sex. Additional adjustments for other known risk factors including education, hypertension, smoking, diabetes, steroid use, sunlight exposure, sedentary lifestyle and multivitamin use did not substantially alter the estimate of risk.
Conclusions: :
The data suggest that living in rural Beaver Dam does not increase risk of age related cataract and may be protective for PSC.
Keywords: cataract • clinical (human) or epidemiologic studies: prevalence/incidence