The statistics relating to type 2 diabetes are quite alarming and this disease threatens to consume a large amount of our limited health resources. When it is considered that it is a disease that is to a large degree preventable, the enormous challenge for GPs is to try to identify those at risk, advise on how to prevent diabetes in those who have abnormal glucose metabolism, and to minimise risk and complications of those with diabetes.
The penalty for being complacent will be the doubling of the prevalence of type 2 diabetes over the next 10 years. There are already 800,000 diabetics in Australia with about 90% type 2s. Half of those are unaware they have the disease. One in four people over the age of 25 years has impaired glucose metabolism. We are now seeing the disease in younger people including children and adolescents. At least 80% of type 2 diabetics are overweight or obese.
New guidelines for screening and diagnosis have just being released in Australia particularly targeting those with a fasting plasma glucose of 5.5-6.9 mmol/L who need a follow up GTT and a significant proportion of these will have diabetes (see guidelines on www.diabetesaustralia.com.au). Patients with impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) usually convert to type 2 diabetes at a rate of 5-10% per year.
After diagnosis
So once identified what can GPs do about the situation? A landmark clinical trial called the Diabetes Prevention Program (DPP) was published in the New England Journal of Medicine this year(1) which showed that those at high risk of developing type 2 diabetes can delay and possibly prevent the disease by lifestyle modification.
The DPP compared three approaches - lifestyle modification, treatment with metformin and standard medical advice in 3,234 overweight people with IGT. Diet and exercise that achieved a modest 5-7% weight loss reduced diabetes incidence by 58% in participants randomised to the study’s lifestyle intervention group. Participants in this group exercised at moderate intensity usually by walking an average of 30 minutes a day on five days a week and lowered their intake of fat and calories. Volunteers randomly assigned to treatment with metformin (850 mgm twice per day) had a 31% lower incidence of type 2 diabetes. A standard group took placebo instead of metformin. Both of the latter two groups also received information on diet and exercise.
Lifestyle intervention worked equally well in men and women and in all ethnic groups. It was most effective in people aged 60 or older who lowered the risk of developing diabetes by 71%. Metformin was also effective in both sexes and in all ethnic groups but was relatively ineffective in older volunteers and in those who were less overweight. The number needed to treat (NNT) to prevent one case of diabetes in three years through lifestyle modification was 7 and NNT for the same period with metformin was 14.The tested interventions were found to be both safe and efficacious.
In a Finnish study(2) 522 middle aged obese subjects with IGT were randomised to receive either brief diet and exercise counselling (control group) or intensive individualised instruction on weight reduction, food intake and guidance on increasing physical activity (intervention group). After an average follow-up of 3.2 years, there was a 58% relative reduction in the incidence of diabetes in the intervention group compared with the control subjects. A strong correlation was also seen between the ability to stop the progression to diabetes and the degree to which subjects were able to achieve one or more of the following: lose weight (goal of 5% weight reduction), reduce fat intake (goal of <30% of calories), reduce saturated fat intake (goal of <10% of calories) increase fibre intake (goal of >/= 15 g/1,000 kcal) and exercise (goal of >150 min/week).
Prevention in general practice
How could the results of this trial be applied to our general practices? Firstly GPs are uniquely placed to opportunistically identify and target at risk people with a GTT according to guidelines. Secondly they can target IGT patients and look at some kind of lifestyle change intervention. This could be one to one input using motivational interviewing, or by referral to other health professionals including dieticians and exercise physiologists. Alternatively there are commercial programs such as GutBusters, Weight Watchers etc. Hopefully government strategies to address the issues that give rise to an obesogenic environment as well as education and health promotion campaigns will also complement the approach for individuals led by GPs.
Admittedly resources that are needed to achieve the goals of 5-10% weight loss amongst our overweight and obese patients are thin on the ground, particularly our own time constraints, but there are also some untapped resources in our region such as students and graduates in Exercise Science and Nutrition at Southern Cross University. Then there are allied health professionals in private practice as well as in the overburdened public sector. Although care plans are slow to be taken up and heavily weighted with administrative obligations there could be potential to use these more in the field of diabetes prevention and better control of diabetes even if it means sharing the generous rebate Medicare fee ($164) with allied health professionals.
Somehow we need to use our creativity and skill to address this critical health problem. GPs are in a position to influence the situation and to have a positive impact in containing this epidemic.
References
(1) Diabetes Prevention Program Research Group. Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin. N Engl J Med. 2002; 393-403.
(2) Tuomilehto J et al, Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance. N Engl J Med 344: 1343-1350, 2001. Dr Andrew Binns
abinns@gmc.net.au
Dr Andrew Binns is a GP with a special interest in obesity issues. He runs Professor Trim weight reduction courses and trains GPs in how to use the program with their patients.
Dr Binns is Adjunct Professor in the Division of Health and Applied Sciences, Southern Cross University. He has an ongoing commitment to research projects with patients who have the metabolic syndrome as well as mechanical and motivational problems. He is also supporting SCU's increasing role in teaching and research in lifestyle approaches to the management of obesity and related complications.
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