High cholesterol in diabetes may harm vision

Aggressive treatment to lower high cholesterol in patients with type 1 diabetes, also known as "juvenile diabetes," an autoimmune disease that typically develops at a young age, could protect their vision as well as their cardiovascular health, a new study suggests.

Harvard researchers found that individuals with the highest levels of low-density lipoprotein (LDL), the "bad" cholesterol, had twice the risk of developing a visual problem called macular edema, or fluid in the macula of the eye, compared with those with the lowest LDL levels.

Subjects with the highest ratio of total cholesterol to high-density lipoprotein (HDL), the "good" cholesterol had a fourfold increased risk of this eye disorder.

Clinically significant macular edema is the leading cause of vision loss in diabetics, Dr. Debra A. Schaumberg of Brigham and Women's Hospital and colleagues note. While high blood sugar has been tied to the development and progression of disease of the retina, the relationship between blood glucose control and clinically significant macular edema is not as clear.

Schaumberg and her colleagues analyzed data from the Diabetes Control and Complications Trial, which included 1,441 patients with type 1 diabetes followed for an average of 6.5 years. Study participants' cholesterol levels were checked annually.

The study, published in the medical journal Diabetes, is the largest investigation of its kind to-date to evaluate the relationship between clinically significant macular edema and blood cholesterol levels.

Patients in the top quarter of total-to-HDL cholesterol ratio had 3.84 times the risk of clinically significant macular edema compared with those in the lowest quarter. Those with the highest LDL levels were 1.95 more times likely to develop clinically significant macular edema.

When the patients' blood sugar levels were considered, the relationship between cholesterol levels and clinically significant macular edema was weaker, although the association remained significant.

However, no relationship was seen between cholesterol levels and the progression or development of diabetic retinopathy.

The results indicate that high cholesterol, especially the total-to-HDL cholesterol ratio, are risk factors for clinically significant macular edema, Schaumberg and her colleagues conclude. The findings may also lend further support to current treatment guidelines that recommend aggressive lowering of high cholesterol in diabetic patients, they add.

SOURCE: Diabetes, November 2004.