Statins and diabetes both increase cataract risk

Patients using cholesterol-lowering statin drugs may be at increased risk of developing age-related cataracts, according to a study - "Age-related Cataract Is Associated with Type 2 Diabetes and Statin Use", in the August issue of Optometry and Vision Science, official journal of the American Academy of Optometry. The journal is published by Lippincott Williams & Wilkins, a part of Wolters Kluwer Health.

While further research is needed to understand the true nature of the association, the additional risk of cataracts in statin users appears similar to that associated with type 2 diabetes, according to the study by Carolyn M. Machan, OD, and colleagues of University of Waterloo, Ont., Canada.

Statins and Diabetes Both Increase Cataract Risk
The study included nearly 6,400 patients seen at the optometry clinic at the University of Waterloo in 2007-08. Of these, 452 patients had type 2 diabetes. Statin treatment and diabetes were evaluated as possible risk factors for age-related cataracts, controlling for other factors including sex, smoking, and high blood pressure.

Fifty-six percent of patients with type 2 diabetes were taking statins, compared to 16 percent of those without diabetes. Both diabetes and statin use were significantly associated with an increased rate of age-related cataracts.

With adjustment for other factors, diabetes was associated with an 82 percent increase in cataract risk and statin use with a 57 percent increase. Statistically, the increase in cataract risk associated with statins was similar to that associated with diabetes.

The associations differed for different types of cataracts. For one specific type long linked to diabetes (posterior subcapsular cataract), the association with diabetes was no longer significant after adjustment for statin treatment.

Despite the high rate of statin use among patients with diabetes, the two risk factors appeared independent of each other. At older ages, the risk of cataracts increased fastest in diabetic patients who took statins and slowest in nondiabetic patients who did not take statins. On average, cataracts developed 5.6 years earlier in diabetic patients who took statins, compared to nondiabetic patients who did not take statins.

Type 2 diabetes is a known risk factor for the development of age-related cataracts—a common vision problem caused by clouding of the crystalline lens of the eye. Studies in animals have shown a clear link between long-term treatment with statins (at high doses) and cataracts.

The new study suggests that statins may also be linked to cataracts in humans. The authors emphasize that the study can't prove that statins play any role in causing cataracts, but suggest that such a link is biologically plausible.

While further studies are needed, Dr Machan and colleagues emphasize that the known benefits of statin treatment for patients with type 2 diabetes probably outweigh any increased risk of cataracts. They believe their results will help to increase awareness of the risks of treatments for type 2 diabetes, and may encourage the development of alternative cholesterol-lowering drugs that are not associated with an increased risk of cataracts.

Anthony Adams, OD, PhD, Editor-in-Chief of Optometry and Vision Science, comments, "Considering the increase in the prevalence of diabetes and the corresponding increase in the use of statins, the authors feel these findings serve to encourage further research on the long-term effect of statins on the human crystalline lens."