Diabetic medication metformin may reduce risk of developing AMD, study suggests

Image, Artem Podrez on Pexels

By Helen Carter

Journalist

The common anti-diabetic medication metformin may help prevent age-related macular degeneration, a large study suggests.

More than five million PBS/RPBS scripts are written annually in Australia for the insulin tablet which is sold under multiple trade names and helps control blood glucose levels in type 2 diabetes.

Optometry Australia’s Chief Clinical Officer Luke Arundel said: ‘If metformin is proven in future studies to have a protective effect against developing AMD, this protective effect would be a welcome bonus for diabetic patients.’

The large case-control study in more than 312,000 people found that metformin use was associated with decreased odds of developing AMD in a dose-dependent manner, with the greatest benefit at low to moderate dosages.

People on doses of more than 1080 g of metformin over two years did not have reduced odds of developing AMD.

Both the reduction in odds ratio and the dose-dependent response were preserved in a cohort consisting only of patients with diabetes.

‘When looking only at patients with diabetes, we saw a preservation of the dose-dependent decrease in the odds of patients developing AMD,’ the American researchers said in JAMA Ophthalmology

‘The use of metformin may protect against the development of AMD and lead to a novel therapeutic strategy for the prevention of this disease.’

However the researchers said metformin did not appear to be protective in patients with diabetes and coexisting diabetic retinopathy.

The study of patients from a nationwide health insurance claims database included a population-based sample of patients. Those aged 55 years and older with newly diagnosed AMD from January 2008 to December 2017 were defined as cases and matched with control participants. Data analyses were completed from June 2019 to February 2020.

Other researchers said, in an invited commentary, that ‘given the burden of vision impairment secondary to advanced AMD, the lack of proven therapies for atrophic AMD, and the burden of treatment associated with neovascular AMD, interventions aimed at preventing AMD are urgently needed.’

They said while ‘findings reported are of great interest,’ results need to be cautiously interpreted in line with limitations at play when conducting case-control studies with administrative data, as acknowledged by the authors.

Metformin is the seventh most prescribed PBS/RPBS drug in Australia by prescription counts, according to PBS/RPBS data compiled by NPS MedicineWise.

Diabetes Australia says it is often prescribed as the first diabetes tablet for people with type 2 diabetes who are overweight and it may help to manage weight.

It belongs to the biguanides group of insulin tablets which lower blood glucose levels by reducing the amount of stored glucose released by the liver. This slows the absorption of glucose from the intestine and helps the body to become more sensitive to insulin so its own insulin works better.