The popular diabetes medication, metformin, may soon be used not just to regulate blood sugar, but to protect against a common form of blindness, called macular degeneration.
Researchers have discovered that people who use metformin to treat type 2 diabetes have a significantly lower rate of age-related macular degeneration (AMD) in comparison to those who do not use this medication.
Dr. Yu-Yen Chen, PhD, of the Department of Ophthalmology, Taichung Veterans General Hospital in Taiwan and lead researcher of the study, and her team found that nearly half as many patients who used metformin had AMD in comparison to those who did not use the drug.
Researchers from the health institutions in Taiwan presented a study with these findings at the 2018 American Academy of Ophthalmology conference in Chicago.
Using the Taiwan National Health Insurance Research Database, Chen and her team collected data on over 68,000 patients recently diagnosed with type 2 diabetes from January 2001 to December 2013.
She divided these patients into those who took metformin, 45,524 people, and those who did not, 22,681 people. After following the groups for 13 years, the scientists attributed the reduction in prevalence of macular degeneration to the use of metformin.
“Our study is the first to reveal the protective effects of metformin on the development of AMD,” said Chen in a released statement by the American College of Ophthalmology.
It has long been known that inflammation and oxidative stress have contributed to both diabetes and age-related macular degeneration. Researchers believe that the suppression effects of metformin on inflammation and oxidative stress is a likely reason for this benefit.
“We’ve known already about the benefits of controlling diabetes on microvascular complications,” said Dr. Robert Courgi, endocrinologist at Southside Hospital in Bay Shore, New York. “This study provides us with greater evidence.”
Macular degeneration is a result of photoreceptor cell death by the retina, and is one of the leading causes of vision loss in the United States.
According to the BrightFocus Foundation, there are currently 11 million people in the United States with some form of age-related macular degeneration. By the year 2050, that number is expected to rise to 22 million.
By 2040, experts predict that almost 288 million people worldwide will have this condition.
Prior to the start of the study, those in the metformin treatment group had a greater prevalence of systemic comorbidities including hypertension, hyperlipidemia, and coronary artery disease. However, after adjusting for gender, age, as well as these comorbidities, this study showed a significantly lower risk of AMD in those who used metformin.
“While the results of this study are certainly interesting, it is the first of its kind to show this relationship,” said Dr. Matthew Gorski, ophthalmologist for Northwell Health in Great Neck, New York.
Metformin is widely used to treat type 2 diabetes. It’s arguably the most prescribed and most cost-effective medication for diabetes, with over 120 million prescriptions worldwide.
The medication works by lowering the amount of sugar that is released by the body, and improving how the body responds to sugar. It also promotes improvements in blood vessel lining dysfunction, oxidative stress, lipid control, and even fat distribution. These additional benefits lend themselves beyond metformin’s blood glucose effects by decreasing adverse cardiovascular outcomes as well.
According to the American Diabetes Association, in 2015, 30.3 million Americans or 9.4 percent of the population had diabetes. Over 1.5 million Americans are diagnosed with diabetes each year. Diabetes remains the seventh leading cause of death in the United States.
“Studies like this make me more aggressive, even with prediabetic patients, and starting them earlier on metformin to prevent full-blown diabetes — it also has the added benefit of preventing eye disease,” Courgi said.
Although this study does give promise to a well-known and tolerated medication that treats diabetes, Gorski does not believe he will start using it for the prevention of macular degeneration yet.
“Additional studies will need to prospectively look at and confirm the relationship between metformin and macular degeneration before I will begin to use it to treat macular degeneration,” he said.
Gorski warned that if you experience any changes in “vision, blurriness, or visual disturbance, it is important to see your eye doctor right away.”
Despite the prevalence of diabetes and its good control with medications, research is still being conducted on the additional benefits of diabetes medications. Recently, researchers at Mount Sinai have shown a potential link between diabetes-medication use and a reduction in Alzheimer’s disease severity.
While the study conducted in Taiwan does show promise, it does not fully show the cause and effect of metformin. Chen agreed that “while more study is required to determine just how metformin protects against the development of AMD, this is an exciting development for patients at risk.”