DIABETES iN cANADA

PREVENTION OF DIABETES AND LONG-TERM COMPLICATIONS

Primary Prevention: Preventing Diabetes

The prevention of Type 1 and Type 2 diabetes requires different strategies, as they have quite different causes. Primary prevention efforts are focused on the reduction of obesity and physical inactivity, which are the known modifiable risk factors for Type 2 diabetes only. Further evaluation of the effectiveness of such programs is required. At this time there are no known modifiable risk factors for Type 1 diabetes. Additional basic research is needed as the etiology of this condition remains unclear.

Secondary Prevention: Early Detection of Diabetes Through Screening

Secondary prevention involves early identification of diabetes through screening to prevent or delay the progression of the disease. In 1994, the Canadian Task Force on the Periodic Health Examination⁽⁴²⁾ recommended against screening for asymptomatic people with Type 2 diabetes. There were two reasons why the Task Force was not in favour of screening for diabetes: (i) the lack of a screening test that combined accuracy with practicality and (ii) the absence of adequate evidence that early detection and treatment improved outcome in asymptomatic people.

In terms of the lack of an appropriate screening test, new studies have been published since the Task Force finalized its report in January, 1994. The report of the American Diabetes Association Expert Committee on the Diagnosis and Classification of Diabetes Mellitus lists three critical sources of information supporting the creation of a new cutpoint for fasting blood sugar for diagnosis⁽⁴³⁾; none of these was available in January, 1994. The sources are McCance's study in Pima Indians⁽⁴⁴⁾, Engelgau's study in Egyptians⁽⁴⁵⁾, and finally the National Health and Nutrition Examination Survey III, which was unpublished in 1994.

With regard to the lack of evidence for improved outcomes in asymptomatic people as a result of early detection and treatment of diabetes, the United Kingdom Prospective Diabetes Study (UKPDS) shows clear evidence that tight glycemic control improves outcome⁽⁴⁶⁾. In conjunction with the previous evidence from UKPDS - that those with previously undiagnosed diabetes (30% of subjects in the study) showed no significant difference in the progression rates for any of the complications or conditions compared with those who presented initially with symptoms of diabetes⁽⁴⁷⁾ - this is more evidence that people with asymptomatic Type 2 diabetes would benefit from screening and treatment. The Canadian Diabetes Association has endorsed screening in select groups (including everyone over the age of 45) in its 1998 clinical practice guidelines⁽¹⁴⁾. It is hoped that the Task Force, now renamed the Canadian Task Force on Preventive Health Care, will revisit this question in the near future.

The positive benefits of screening for Type 1 diabetes have not been established and with the potential for negative psychosocial effects, it is not recommended for this group.

Tertiary Prevention: Preventing or Delaying the Complications of Diabetes

Tertiary prevention is aimed at delaying or preventing the development of complications in people who already have diabetes. A landmark trial investigating people with Type 1 diabetes showed that good glycemic control can reduce the likelihood of microvascular complications leading to blindness or kidney disease, but the trend toward a decrease in macrovascular disease was not statistically significant⁽⁴⁸⁾. The UKPDS⁽⁴⁹⁾ has shown that tight control of blood sugar and blood pressure reduces the rate of microvascular disease and macrovascular disease (heart disease or stroke) in people with Type 2 diabetes. The treatment of hyperlipidemia also prevents the development of macrovascular disease in people with diabetes. For all people with diabetes, regular foot and eye examinations with proper preventive treatment can prevent amputations and progression of retinopathy.

Education: Key Role in Tertiary Prevention

Diabetes education of health care professionals and those affected by diabetes plays a key role in the tertiary prevention of the disease. Canadian data are lacking on how many people with diabetes receive education on self-management of their condition. A US National Health Interview Survey found that only 35% of people with diabetes had attended a class or program about diabetes⁽⁵⁰⁾.

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