Several risk factors for CV disease are also risk factors for cataract….
Cataracts are the main cause of low vision and blindness. Statins are commonly prescribed for the prevention of cardiovascular diseases; however, they may do so at the risk of obstructing vision. In this study, researchers compared the risks for cataract development between statin users and nonusers within a military health care system where patients have equal access and standards of health care. There were 13,626 statin users and 32,623 nonusers included in the study. For baseline inclusion, they identified patients enrolled in the system between Oct. 1, 2003 and Sept. 30, 2005. The follow-up period for identifying occurrence of cataracts was between Oct. 1, 2005 and March 1, 2010. An event was defined as the occurrence of an ICD-9-CM code during follow-up in either the inpatient or outpatient setting consistent with a cataract diagnosis.
Among patients who satisfied the study selection criteria, statin users were older, more likely to be male, more likely to be obese, used tobacco more frequently, had higher CCI total score, used more medications, and used health care more frequently. For the primary analyses, the authors created a propensity score–matched cohort of 6972 pairs of statin users and nonusers. There were no significant differences in baseline characteristics between statin users and nonusers after matching. The mean (SD) of cumulative duration of statin use among statin users was 1593 (696) days. The mean (SD) of cumulative simvastatin years was 141.8 (133) mg years.
The risk for cataract was higher among statin users in comparison with nonusers in the propensity score-matched cohort (odds ratio, 1.09; 95% CI, 1.02-1.17). In a secondary subgroup analysis of 33,513 patients (6,113 on statins) who had no comorbidity, based on the Charlson comorbidity index, the use of statins remained significantly associated with cataracts (OR 1.27, 95% CI 1.15-1.40). Sensitivity analysis confirmed this relationship.
Several observational studies investigating the association of statin therapy with cataracts have produced conflicting results, with some reporting a protective effect, a negative effect, no effect, and an inconsistent effect. An important consideration in observational studies is the presence of baseline confounders that may mask an actual relationship or falsely demonstrate the presence of relationship. Adherence to statins may be a marker for a healthy user bias that may result in false association of statin use with better outcomes. Several risk factors for cardiovascular disease (e.g., older age, diabetes mellitus, and smoking), which constitute indications for statin therapy, are also risk factors for development of cataract. Based on the results of this study, the authors suggest that the risk-benefit ratio of statin use, specifically for primary prevention, should be carefully weighed.
- The risk for cataract is increased among statin users as compared with nonusers.
- Cataracts are the main cause of low vision and blindness.
- Adherence to statins may be a marker for a healthy user bias.