Attributable risk estimates for cataract to prioritize medical and public health action

Abstract

Purpose: Cataract is the most common cause of blindness in the world. The purpose of this study was to estimate the population attributable risk associated with identified risk factors for cortical, nuclear, and posterior subcapsular (PSC) cataract in a representative sample of the Victorian population aged 40 years and older.

Methods: Cluster, stratified sampling was used and participants were recruited through a household census. At locally established test sites, standardized clinical examinations were performed to assess cataract and personal interviews were conducted to quantify potential risk factors. Multivariate logistic regression was used to determine the independent risk factors associated with the three types of cataract, and the population attributable risk was calculated.

Results: A total of 3271 (83% of eligible) of the urban residents and 1473 (92%) rural residents participated. The urban residents ranged in age from 40 to 98 years (mean, 59 years), and 1511 (46%) were men. The rural residents ranged in age from 40 to 103 years (mean, 60 years), and 701 (48%) were men. The overall prevalence of cortical cataract was 12.1% (95% CL 10.5, 13.8), nuclear cataract 12.6% (95% CL 9.61, 15.7), and PSC cataract 4.93% (95% CL 3.68, 6.17). Significant risk factors for cortical cataract included age, female gender, diabetes for greater than 5 years, gout for greater than 20 years, arthritis, myopia, average annual ocular UV-B exposure, and family history of cataract (parents or siblings). Significant risk factors for nuclear cataract included age, female gender, rural residence, age-related maculopathy, diabetes for greater than 5 years, smoker for greater than 30 years, and myopia. The significant risk factors for PSC cataract were age, rural residence, thiazide diuretic use, and myopia. Of the modifiable risk factors, ocular UV-B exposure explains 10% of the cortical cataract in the community, and cigarette smoking accounts for 17% of the nuclear cataract.

Conclusions: Because of the near universal exposure to UV-B in the environment, ocular protection has one of the highest modifiable attributable risks for cortical cataract and would therefore be an ideal target for public health intervention. Quit smoking campaigns can be expanded to incorporate information about the excess cataract in the community associated with long-term smoking. Nonmodifiable risk factors such as age, gender, and long-term medication use have implications for the timely referral and treatment for those at higher risk of cataract.