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Test can’t always tell if diabetics fit to drive

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The measure of tight sugar control that’s used to assess diabetic drivers doesn’t take into account hypoglycemia, which can cause blackouts, researcher says

By the year 2020, the number of Canadians afflicted with diabetes will jump to an estimated 3.7 million, up from 2.5 million today – and that does not bode well for road safety.

Diabetes can lead to a host of medical complications such as heart attacks, strokes, blindness and temporary loss of consciousness that may impair a person’s ability to drive.

So, how do you know if someone is fit enough to be in the driver’s seat? A study released this week suggests it is not an easy task. In fact, existing measures to determine driver eligibility may be seriously flawed.

In most provinces, diabetics must undergo a specific blood test to qualify for a commercial driver’s licence. And, under circumstances in which driving abilities are in doubt, the test may be required to maintain a private licence.

The test, known as HbA1c, is a standard measure of blood-glucose levels over a 90-day period. It’s generally assumed that good blood-sugar management, or “tight glycemic control,” is best for long-term health. That’s because sharp spikes in glucose levels can damage blood vessels and contribute to the development of cardiovascular disease and vision loss.

But the new study, led by Donald Redelmeier, a professor of medicine at the University of Toronto, found that diabetics with tight glycemic control were at a higher risk of being in a vehicle crash than those with mediocre blood-sugar control.

“[HbA1c is] probably the single most widely accepted test for measuring how well a diabetic adult is doing with their diet, their exercise and their blood-sugar management,” Dr. Redelmeier said. “But contrary to legal theories, those adults with better blood-sugar control had, paradoxically, a higher risk of a crash.”

That essentially means the HbA1c test by itself isn’t a reliable guide to who may be fit to drive.

The study, published in the online journal PLoS Medicine, is based on Ontario data on 795 diabetic drivers. It found that one in 14 had been involved in collisions over a two-year period.

So, why would good glucose control put a diabetic at increased risk of a crash? In some cases, Dr. Redelmeier said, the medications used to prevent elevated blood-glucose levels can trigger hypoglycemia – or low blood sugar – which can cause dizziness, mental confusion and even loss of consciousness. And it’s certainly not safe to black out while driving a vehicle.

Unfortunately, there’s no blood test to accurately measure the frequency of hypoglycemia, said Dr. Redelmeier, who is a staff physician at Sunnybrook Health Sciences Centre in Toronto. And some diabetics may be reluctant to admit having these episodes if it means they could lose their driver’s licence.

Dr. Redelmeier stressed that lives can be ruined by a momentary lapse of concentration that leads to a crash.

He has the following advice for diabetics hoping to reduce their odds of a collision: a) Don’t assume you’re risk-free if you get a good grade on the HbA1c test; b) Check your blood-sugar levels before starting out on a long drive, and c) Keep glucose-boosting snacks in the car, even on short excursions, because there’s always the chance of getting stuck in a traffic jam.

All clear on cellphones

Despite some public fears that cellphones can cause brain tumours, a European study found no evidence that this type of cancer is on the rise.

The researchers, led by Isabelle Deltour of the Institute of Cancer Epidemiology in Copenhagen, analyzed cancer statistics from Demark, Finland, Norway and Sweden for the period between 1974 to 2003. The use of mobile phones increased sharply in the mid-1990s. So, the study period includes both the time before and after the devices became commonplace in Scandinavia.

The study, published in the U.S.-based Journal of the National Cancer Institute, showed no change in incidence trends for brain tumours from 1998 to 2003.

Even so, the findings won’t likely put an end to speculation about cellphones and cancer. The authors acknowledge it may take many more years of exposure for an increased cancer risk to become apparent. Or the effect may be too small to be detected in a study of this size.

Coffee versus cancer

Can drinking copious amounts of coffee increase a man’s odds of avoiding the most lethal forms of prostate cancer?

Researchers scrutinized the coffee consumption of almost 50,000 men taking part in the Health Professionals Follow-Up Study – a major effort to chart how various nutritional and lifestyle factors influence long-term health. Over a 20-year period, 4,975 men developed prostate cancer.

The analysis showed that men who drank the most coffee had a 60-per-cent lower risk of developing an aggressive – and potentially deadly – type of prostate cancer than men who did not drink coffee.

The scientists, who presented their findings this week at a meeting of the American Association for Cancer Research in Houston, can’t say how coffee may shield men from aggressive prostate cancer. But the lead researcher, Kathryn Wilson of Harvard Medical School, noted: “Coffee has an effect on insulin and glucose metabolism as well as sex hormone levels, all of which play a role in prostate cancer.”

Nonetheless, this type of study can’t prove a direct link between coffee consumption and prostate-cancer risk. It’s possible that the men who were less likely to develop aggressive cancer also had other lifestyle factors in common. The coffee connection may simply be a coincidence.

Even if the effect is real, men may have to drink an awful lot of coffee to reap the benefits: The top coffee drinkers in the study downed six or more cups a day of either regular or decaffeinated brew.

CTVglobemedia Publishing, Inc

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