Metformin Users Bannister Study.

Metformin Users Lived Longer In Bannister Study

Summary:  Can the diabetes drug metformin use help us live longer?  While metformin users lived longer in the Bannister study, others disagree. This article explains both sides of the metformin use debate. [This article first appeared on the website. Author: Brady Hartman. ]

Metformin is a wildly popular medication used to treat type 2 diabetes. Derived from the French lilac, or Galega officinalis, also known as Goat’s Rue, the herbal remedy has been used since medieval times for frequent urination, a well-known symptom of diabetes.

Metformin has been prescribed since the mid-1950’s as a treatment for people with type 2 diabetes. A large body of evidence shows that it is more effective than similar drugs. The Bannister study is one such piece of evidence. It reported sensational results and remains controversial to this day. Metformin use is expected to grow as the number of type 2 diabetics increases.

Metformin users lived longer.
Bannister showed that metformin users lived longer. Photo: Pixabay.

Bannister Compares Metformin Use

Published in late 2014, the Bannister Study took the anti-aging world by storm when it showed that most diabetics using metformin lived just as long as healthy people. An astonishing result, because type 2 diabetics usually die ten years earlier than healthy people.

The Bannister Study was a head to head comparison between two drugs used in the treatment of type 2 diabetes: 12,000 diabetics on sulphonylurea (SU), and 78,000 diabetics using metformin. Each group was paired with an equivalent number nondiabetic controls who were matched for age, smoking and cancer history.

The 12,000 sulphonylurea-treated diabetic patients had 40 percent greater mortality than their 12,000-strong non-diabetic control group. The researchers weren’t surprised, because, on average, type 2 diabetics live shorter lives than non-diabetics. The 78,000 diabetic metformin users lived about the same as their 78,000-strong nondiabetic control group, despite the fact that the participants with type 2 diabetes were heavier and had more health problems when the study began. A remarkable finding, given that people with diabetes usually die ten years earlier than ordinary people on average. Even more remarkable was the discovery that the metformin users over the age of 70 lived longer their matched nondiabetic control group.

The authors of the Bannister study concluded:

  1. Metformin use is superior to sulphonylurea.
  2. The metformin users had reduced rates of cancer and heart disease.
  3. The researchers also suggested that because the metformin users lived just as long their matched nondiabetic control group, that metformin may be used as an anti-aging drug by ordinary people, helping those without diabetes live longer.
The Bannister study had design flaws.
The Bannister study had some design flaws. Photo: Pixabay.

Opposing Viewpoint

In a commentary, Andrea V Margulis, MD, and colleagues claim that the Bannister study had two design flaws that may have skewed the results.  Because Bannister was an observational study rather than a clinical trial, the authors created three artificial study groups, called cohorts. The three groups are metformin users, non metformin users, and nondiabetics – healthy people used as controls.

A flaw in the Bannister design – that may also have skewed results – is the diabetics in the metformin users group were healthier. As their diabetes disease progressed, they left the metformin users group, and presumably were placed into the non metformin users group. Dr. Margulis and team said that:

“Although the results from Bannister et al. are intriguing, we wonder whether study design features might have created a cohort [study group] of patients with diabetes that selectively retained healthier individuals [metformin users group], while the same was not true for the cohort without diabetes to which they were compared.”

Another side effect is that the Bannister design unintentionally censored study participants. Censoring is a technical term that means “removing a study participant from the survival curve at the end of their follow-up time.” The unintentional practice of censoring reduced the sample size which the reduced reliability of the study results. Dr. Margulis said:

“To identify the effect of metformin or sulfonylurea monotherapy, follow-up of treated patients with diabetes was censored after any modification to the initial treatment. Thus, as patients with diabetes [metformin users] progressed to the point they needed treatment intensification, they left the cohort [study group].  In contrast, the patients without diabetes [healthy controls] would not have the chance to be excluded from the cohort [study group] in a similar manner with any progression from a starting point of good health. This censoring is tied to the mortality outcome since if a patient with diabetes dies, the matched comparator patient [healthy controls] cannot leave the cohort until he or she dies.”

Take Home Message

Despite the flaw in its design, the Bannister study showed that metformin is superior to sulphonylurea and that is why metformin is the most popular treatment for type 2 diabetes today.

Since the Bannister study, other studies have shown that metformin has many other health benefits. Metformin use helps prevent diabetes in prediabetics. As well, studies have shown that diabetic metformin users have reduced rates of cancer and heart disease. The research showing that metformin prevents cancer – reducing risk by nearly a third is covered in the linked article.

The claim that metformin use may help healthy people live longer hasn’t been proven. For the verdict, we will have to wait for the results of the Taming Aging with Metformin (TAME) study, a randomized controlled trial testing metformin’s anti-aging abilities on a group of 3,000 healthy, nondiabetic senior adults. TAME will see if metformin use can delay aging.

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1) Diagnosis, Advice, and Treatment:  This article is intended for informational and educational purposes only and is not a substitute for professional medical advice. The information provided in this article should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. Do not start or stop taking any medication based on what you have read in this article. A licensed physician should be consulted for the diagnosis and treatment of any and all medical conditions. Call 911, or an emergency hotline number, for all medical emergencies. As well, consult a licensed physician before changing your diet, supplement or exercise programs.  2) Photos, External Links & Endorsements: This article is not intended to endorse companies, organizations or products. Links to external websites, depiction/mention of company names or brands, are intended only for illustration and do not constitute endorsements.

Article Sources

A. Bannister, S. E. Holden, S. Jenkins-Jones, C. Ll. Morgan, J. P. Halcox, G. Schernthaner, J. Mukherjee, C. J. Currie. Can people with type 2 diabetes live longer than those without? A comparison of mortality in people initiated with metformin or sulphonylurea monotherapy and matched, non-diabetic controls. Diabetes, Obesity Metabolism. 16, 1165–1173. 31 July 2014. DOI:10.1111/dom.12354 Available Online.