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1384.6 - Statistics - Tasmania, 2002  
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Feature Article - Diabetes mellitus


Contributed by Kris Hazelwood, Manager Diabetes Unit, Menzies Centre for Population Health Research.

Diabetes is a disorder of metabolism - the way our bodies use digested food for growth and energy.

Most of the food we eat is broken down into glucose, the form of sugar in the blood, which is the main source of fuel for the body. After digestion, glucose passes into the bloodstream, where cells for growth and energy use it. For glucose to get into cells, insulin must be present. Insulin is a hormone produced by the pancreas, a large gland behind the stomach.

In people with diabetes the pancreas either produces little or no insulin, or the cells do not respond appropriately to the insulin that is produced. Glucose builds up in the blood, overflows into the urine, and passes out of the body. Thus, the body loses its main source of fuel even though the blood contains large amounts of glucose.

WHAT ARE THE TYPES OF DIABETES?

The three main types of diabetes are:

  • Type 1 diabetes (previously known as insulin dependent diabetes or juvenile onset diabetes)
  • Type 2 diabetes (previously known as non-insulin dependent diabetes or adult onset diabetes)
  • Gestational diabetes.

Type 1 diabetes

Type 1 diabetes is an autoimmune disease. An autoimmune disease results when the body's system for fighting infection (the immune system) turns against a part of the body. In diabetes, the immune system attacks the insulin-producing beta cells in the pancreas and destroys them. The pancreas then produces little or no insulin. Someone with type 1 diabetes needs to take insulin daily to live.

Symptoms of type 1 diabetes usually develop over a short period, although beta cell destruction can begin years earlier. Symptoms include increased thirst and urination, constant hunger, weight loss, blurred vision, and extreme fatigue. If not diagnosed and treated with insulin, a person can lapse into a life-threatening diabetic coma, also known as diabetic ketoacidosis.

Type 2 diabetes

The most common form of diabetes is type 2 diabetes. This form of diabetes is linked to a number of genes. About 80% of people with type 2 diabetes are overweight. Type 2 diabetes is often part of a metabolic syndrome (Syndrome X) that includes obesity, elevated blood pressure, and high levels of blood lipids. Unfortunately, as more children become overweight, type 2 diabetes is becoming more common in young people.

When type 2 diabetes is diagnosed, the pancreas is usually producing enough insulin, but, for unknown reasons, the body cannot use the insulin effectively, a condition called insulin resistance. After several years, insulin production decreases. The result is the same as for type 1 diabetes - glucose builds up in the blood and the body cannot make efficient use of its main source of fuel.

The symptoms of type 2 diabetes develop gradually. They are not as sudden in onset as in type 1 diabetes. Some people have no symptoms until complications associated with diabetes occur. Symptoms may include fatigue or nausea, frequent urination, unusual thirst, weight loss, blurred vision, frequent infections, and slow healing of wounds or sores.

Gestational diabetes

Gestational diabetes develops only during pregnancy. Though it usually disappears after delivery, the mother is at increased risk of getting type 2 diabetes later in life.

WHAT IS IMPAIRED GLUCOSE METABOLISM (IGM)?

People with impaired glucose metabolism, a state between 'normal' and 'diabetes', are at risk of developing diabetes, heart attacks, and strokes. There are two forms of impaired glucose metabolism, impaired fasting glucose and impaired glucose tolerance.

Impaired fasting glucose

A person has impaired fasting glucose (IFG) when fasting plasma glucose is higher than normal but less than the level indicating a diagnosis of diabetes.

Impaired glucose tolerance

Impaired glucose tolerance (IGT) means that blood glucose during the oral glucose tolerance test (when your blood glucose levels are measured after you are given a sweet drink) is higher than normal but not high enough for a diagnosis of diabetes. That is, the fasting glucose level is normal but the blood test following the drink is above normal. With IGT there is a one in four chance of developing diabetes.

COMPLICATIONS

The complications of untreated diabetes include blindness, heart disease, amputation and kidney disease.

PREVALENCE OF DIABETES IN TASMANIA

The Australian Diabetes, Obesity and Lifestyle Study (AusDiab), was the first national study to determine the prevalence of diabetes, obesity and other cardiovascular disease risk factors including hypertension and abnormal serum lipid profiles.

This study has shown that 8.7% of Tasmanians have diabetes.

Age adjusted prevalence rates for diabetes in Tasmania are:
  • 9.0% of males
  • 8.4% of females

Total IGM (includes IGT and IFG) for Tasmania is 17.5 %:
  • 18.3% of males
  • 16.7% of females

As Tasmania is an ageing State the comparison in statistics are adjusted to the 1998 Australian population.

Total prevalence of diabetes:
  • Tasmania 8.3%
  • Nationally 7.5%

Total prevalence of IGM:
  • Tasmania 17.6%
  • Nationally 16.3%

Total diabetes and IGM:
  • Tasmania 25.9%
  • Nationally 23.8%

The study has 95.0% confidence levels which brings the figures in Tasmania for:
  • diabetes 8.7% (5.4 - 11.9)
  • IGM 18.0% (15.3 - 20.6)
  • Total (diabetes and IGM) 26.6 % (21.5 - 31.8%)

THE TASMANIAN INSULIN-TREATED DIABETES REGISTER

The Register was established with a grant from the International Diabetes Institute (IDI) and Novo-Nordisk Australia in 1983. It functioned under the University of Tasmania, Department of Community Health until January 1988. At this time, it became a Division of the newly established Menzies Centre for Population Health Research. Since that time, small grants from several drug companies and IDI have been used to continue the work of the Register.

All Tasmanian residents who use insulin to treat their diabetes are invited to register, and the Register therefore includes both Type 1 and Type 2 diabetes cases of all ages.

Information available on over 2,810 registrants includes:
  • Demography (name, address, contact phone numbers, date of birth, country of birth, countries of parents’ birth)
  • Status (Current <65; Current>64; Deceased; Interstate; Stopped insulin; Living in nursing home; address unknown; no further contact requested)
  • Source information (Tasmanian residency, insulin status, treating doctor, any hospitalisation)
  • Diabetes history (date of diagnosis, current height and body weight, body weight at diagnosis, symptoms at diagnosis, family history of diabetes)
  • Treatment history (initial treatment, insulin treatment history, current treatment)
  • Diabetes complications (any diabetes related complications, other disorders, medications)
  • Diabetes management (blood glucose monitoring, frequency of visits to doctor, diabetes educator, dietitian, podiatrist, frequency of eye checks)
  • Education and employment (years of education, employment status and occupation, partner’s employment status and occupation)
  • General health (smoking status, alcohol intake, physical activity)

As at February 2002, of the 2,810 registrants:
  • 1,630 (1,252 under 65 years of age) were living in Tasmania (for whom there was an address)
  • 290 had either moved interstate, had nursing home placement or there was no longer a forwarding address
  • 846 were deceased
  • 34 were no longer using insulin to maintain blood glucose levels

The remaining 10 declined to complete the paperwork and were subsequently removed from the Register.

DIFFERENT REGISTERS

The National Diabetes Registry (NDR) held at the Australian Institute for Health and Welfare in Canberra, obtains its information about a person with diabetes from the National Diabetic Services Scheme (NDSS) database if the person signs the consent section on the NDSS registration form. NDSS is a Commonwealth Government program that provides people with diabetes blood and urine testing strips, syringes and needles at subsidised prices to those who register.

Unlike the NDR, the Tasmanian Diabetes Insulin Treated Register is a volunteer register relying on doctors, diabetes educators and pharmacies to convince the individual with diabetes of the value of joining this Register. The Register held at the Menzies Centre collects information, from people with Type 1 and Type 2 (using insulin therapy), for research into the causes, treatment, prevention and cure of diabetes as well as the availability and utilisation of appropriate community resources (e.g. diabetes educators, podiatrists).

DIABETES RESEARCH PAST AND PRESENT

Anti-Gad Study

This study began in 1992 and is currently suspended. This study obtained population-based data on the blood level of antibodies to glutamic acid decarboxylase (anti-GAD) in people with diabetes and their first degree relatives. Blood samples have been collected from over 1,259 people on the Register, and 900 of their first degree relatives. If you have diabetes, the presence of anti-GAD antibodies means that you most likely have Type 1 diabetes. Relatives who are anti-GAD antibody positive face a greater risk of developing Type 1 diabetes in the future, but the exact risk is not yet known.

Tasmanian Diabetes and Kidney Follow-up Study

In 1991 the Centre conducted a cross-sectional study, which suggested that dietary intake might be associated with the development of impaired kidney function. At that time both kidney function and dietary intake were measured in relation to other factors relating to their health and lifestyle.

This finding was followed up in 1999 courtesy of a grant from the NHMRC (National Health and Medical Research Council). The aim of this study was to:
  • follow up individuals with Type 1 diabetes who had no signs of impaired kidney function in the 1991 Study
  • ascertain those who had developed impaired kidney function
  • compare those who did develop to those who did not develop impaired kidney function.

Tasmanian Diabetes Family Study (TDFS)

Funded by the biotechnological company, Autogen Pty Ltd through the International Diabetes Institute, this Study aimed to identify genes that may contribute to Type 2 diabetes and the metabolic syndrome, which includes hypertension, obesity and dyslipidaemia.

This Study commenced in October 1999 and was completed in August 2001. The selection criteria were to involve families that had 4 or more closely linked family members with Type 2 diabetes.

Information on more than 1,600 individuals was collected. In total 905 individuals (probands and family members) had measurements taken and questionnaire details (if returned) recorded.

Measurements involved:
  • Height, weight, body mass index
  • Bioelectrical Impedance Measurement
  • Blood pressure.

Blood samples were collected from 860 individuals for DNA, anti-GAD and pathology analysis.

Pathology tests included:
  • Serum urea, creatinine, urate, cholesterol, triglycerides, LDL/HDL
  • HbA1c
  • Fasting glucose or Oral Glucose Tolerance Test
  • Insulin and C-Peptide
  • Urinary creatinine, protein and albumin.

Questionnaires focused on medical history, lifestyle and dietary regime. Out of the 670 family members who believed they did not have diabetes, 85 were diagnosed with diabetes or IGT.

The International Diabetes Institute is currently analysing the data.

Research Into Syndrome X (R.I.S.X.)

Funded by Autogen, the Menzies Centre is working with the International Diabetes Institute to investigate the clustering of cardiovascular risk factors associated with Syndrome X, a condition which links Type 2 diabetes and an excess risk of coronary heart disease (CHD).

Metabolic Syndrome X is a group of disorders that include abnormal blood fats (such as elevated cholesterol), obesity, high blood pressure, insulin resistance (the inability to properly deal with dietary carbohydrates and sugars), glucose intolerance, and abnormally high insulin levels that all result from the primary disorder of insulin resistance. The predisposition for insulin resistance is inherited, but in an individual who inherits this tendency, the actual development of Syndrome X usually requires obesity and a sedentary lifestyle.

The cluster of risk factors associated with Syndrome X have a cumulative effect, meaning one factor can influence the development of another (e.g. obesity will sooner or later increase blood pressure) and that two or three of these factors such as high levels of cholesterol plus high blood pressure increase the risk of developing diabetes and/or heart disease far more than just one factor.

This study, which began in October 2001, aims to investigate the clustering of cardiovascular risk factors associated with Syndrome X and to identify which inherited factors linked to these risk factors are shared in large families.

The RISX study was divided into two phases. The first phase, based on the original research plan, was completed in September 2002. During this time, information about the study and its selection criteria was distributed throughout Tasmania through media and community resources.

Individuals that volunteered their family for the study were asked to complete family forms, which staff used to contact family members in order to ascertain available numbers and the level of their interest to participate.

To date there are over 2500 family names recorded on the database. The majority of these belong to seven families. The Centre’s genealogist, Annette Banks, has used her established resources to bring together family data and logically connect family branches for analysis.

As usual, Tasmanians have shown great generosity in giving their time and family information to assist research. Unfortunately some of the families that have volunteered do not meet the study criteria due to insufficient family numbers or lack of interest by family members to take part in the research. All information from these families has been stored securely on our database unless otherwise requested.

A second planned phase is yet to be completed given the high costs of genetic analysis.



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