What do the studies really say about Type 2 diabetes drugs?

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Cait O’Sullivan travelled all the way across the continent a few weeks ago to ask a question that’s been haunting her for years.

It’s her job to know how drugs work, and this was her chance to confront the regulators.

It was a public meeting at the FDA’s Washington, D.C., headquarters, and Health Canada officials would be there.

The main item on the agenda? Drug approval for Type 2 diabetes.

O'Sullivan

Cait O’Sullivan of the B.C. Ministry of Health is not the first to challenge the basis for tight blood sugar control in the treatment of Type 2 diabetes. (CBC)

O’Sullivan wanted them to state, on the public record, what scientific evidence they were using to support their approval of drugs for Type 2 diabetes.

Because O’Sullivan has read the literature and she can’t find it.

After the meeting she flew back home to Vancouver Island empty handed.

“I stood up to ask my question, and they said no more questions.” O’Sullivan said. “It was a disappointing experience.”

But O’Sullivan is not the first to challenge the basis for tight blood sugar control in the treatment of Type 2 diabetes.

A Cochrane review in 2013, a BMJ paper in 2014, and most recently a literature review from the Mayo Clinic in Rochester, Minn., have all investigated the evidence and found it lacking.

It matters because millions of people are taking these drugs.

The theory is that using medication to tightly control blood sugar in type 2 diabetes will prevent the deterioration of tiny blood vessels which can lead to damage in kidneys, eyes and other parts of the body, a composite outcome called “microvascular complications.”

But curiously, the studies failed to show a corresponding drop in the risk of blindness, nor a reduction in the rate of kidney failure.

And none of the studies have shown that tight glucose control reduces the risk of frightening complications like stroke, fatal heart attacks, or death from all causes .

One small positive finding persists: a slight reduction in the risk of a non-fatal heart attack. But the risk of death from heart attack doesn’t change.

Diabetic supplies used by patients

Drugs are part of the treatment regimen for millions of people with Type 2 diabetes. (Celso Pupo)

What some researchers are asking is whether the evidence justifies millions of people taking drugs for decades, and risking side effects, which can include weight gain and the possibility of serious hypoglycemia, which can cause coma and death.

Same data, different interpretations

In medical journalism, it’s a major challenge trying to reflect the uncertainty that is inherent in biomedical research. There’s a perception that science delivers straightforward, objective answers.

But interpretations can be surprisingly subjective, even though everyone is using the same data.

Witness the raging debate over the use of statins that has pitted two of the world’s most prestigious medical journals in an increasingly heated argument over the evidence for some of the most commonly prescribed drugs in the world.

The debate over tight glucose control in type 2 diabetes has been less public, but it has been simmering in the professional community for years.

No one is suggesting that the drugs be tossed out, or that attention to glucose control should be recklessly abandoned.

In his paper, Dr. Victor Montori called for a “careful and thoughtful recalibration,” saying “a skeptical view may be necessary.”

Decades ago, a patient would be diagnosed with Type 2 diabetes based on symptoms of acute high blood sugar including excessive thirst, frequent urination, and blurred vision. Experts still agree that those symptoms should be immediately treated with glucose lowering drugs.

The evidence gap

But today, most patients have no symptoms. They find out they have Type 2 diabetes after a routine blood test. Should they also be given drugs to hit the tight glucose levels? This is where the evidence gap lies.

Back in her home on Vancouver Island, Cait O’Sullivan continues her work for the B.C. Ministry of Health, educating family doctors about the evidence behind the drugs they’re prescribing.

‘[Doctors] look at me as though they’ve never heard of the inquiry into the science behind it.’ – Cait O’Sullivan, B.C. Ministry of Health

When she tells them about the debate over type 2 diabetes drugs, they are often surprised.

“They look at me as though they’ve never heard of the inquiry into the science behind it,” she said.

It’s a debate that can only be resolved with more study and better data. That’s why O’Sullivan’s group is calling on Health Canada to demand better evidence when they approve type 2 diabetes drugs.

Right now Health Canada only requires evidence that the drugs lower blood sugar, and don’t increase the risk of cardiovascular disease.

“What we would need is evidence that the drugs improve the longevity of people’s lives or reduce their risk of developing any disability associated with diabetes,” O’Sullivan said.

But those questions are unlikely to be asked if the belief persists that they’ve already been answered.

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What do the studies really say about Type 2 diabetes drugs?

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