Type 1 diabetes mellitus

Diabetes mellitus is defined as a group of metabolic disorders which either are caused by inadequate insulin secretion (type 1), resistance to the action of insulin (type 2), or a combination of these factors. 

The effect of insulin deficiency or resistance is a persistent elevated level of glucose in the blood stream, which causes a variety of harmful effects. The term diabetes mellitus comes from Latin, ‘diabetes’ meaning to pass through, and ‘mellitus’ meaning honeyed or sweet.

Diabetes is one of the most common chronic diseases and its prevalence is on the increase.¹ The total number of people currently living with diabetes in Ireland is estimated to be 225,840.²

Type 1 diabetes is defined as an absolute insulin deficiency, which occurs when insulin-producing cells in the pancreas are destroyed. This results in an inability to secrete insulin into the body. The most common cause of cell destruction is autoimmunity. The absence of insulin allows persistent elevated levels of glucose (hyperglycaemia) to circulate in the blood, which can cause both chronic and acute complications. People with type 1 diabetes must receive insulin replacement otherwise they would die within days or weeks.

In comparison, type 2 diabetes is classified as insulin resistance along with a relative insulin deficiency, which results in persistent hyperglycaemia. Type 2 diabetes can be managed using a stepwise approach with a combination of diet and lifestyle changes, oral antidiabetic drugs, and insulin.

Type 1 diabetes can occur at any age, although it most commonly presents in children and young people. Incidence peaks in early childhood (age six months to five years) and again during puberty.³ Currently there are approximately 14,000-16,000 people living with type 1 diabetes in Ireland.²

The term type 1 diabetes has replaced older labels such as ‘insulin-dependent diabetes mellitus’ and ‘juvenile-onset diabetes’, which are considered potentially misleading as type 1 diabetes can develop during adulthood and some people with type 2 diabetes are treated with insulin.

Risk factors include a combination of genetic and environmental factors. About 15% of people diagnosed with type 1 diabetes have a first-degree relative (parent, sibling or child) with the condition.⁴ There is some evidence that suggests that in genetically susceptible people, unknown infectious agents or some features of diet in early childhood can trigger the development of autoimmunity which then causes type 1 diabetes.⁵ Further research is needed in this area to confirm the true cause of the disease. 

Diagnosing type 1 diabetes

According to NICE guidelines on type 1 diabetes,¹ the disease should be diagnosed largely on clinical grounds. The NICE criteria for suspecting type 1 diabetes include if a person presents with hyperglycaemia (random plasma glucose more than 11mmol/L) and one or more of the following: ketosis, rapid weight loss, aged under 50 years at onset, a body mass index (BMI) below 25kg/m², or personal and/or family history of autoimmune disease.

In a child or young person, type 1 diabetes should be suspected if the child presents with hyperglycaemia (random plasma glucose more than 11mmol/L) and characteristic features of polyuria (abnormally large volume of urine), excessive thirst, weight loss or excessive tiredness.³ If diabetes is suspected the person should be immediately referred to a diabetes specialist team or a paediatric diabetes care team.

Complications

A variety of potential complications can occur in people with type 1 diabetes. The risk of complications is greatly reduced by keeping circulating glucose levels to as near normal as possible in order to reduce tissue damage. Indeed, disability from complications can often be prevented by early detection and active management.

Approximately one in four people with diabetes will develop chronic kidney disease during their lifetime. Kidney disease accounts for 21% of deaths in people with type 1 diabetes. Diabetes is a leading cause of preventable blindness in people of working age. Diabetic retinopathy accounts for approximately 7% of people who are registered blind in the UK.¹

People with diabetes are estimated to be up to 30 times more likely to have an amputation compared with the general population. Cardiovascular risk is also increased; people with diabetes are at a higher risk of stroke and myocardial infarction.¹

Mental health can also be affected and can include conditions such as anxiety, depression and eating disorders. In children and young people, behavioural and conduct disorders can present, as well as risk-taking behaviour, which can include non-adherence to recommended treatment.

Although the life expectancy for people with type 1 diabetes has generally increased, it is still lower than that of the general population.

Assessment and examination

An initial diabetes assessment should include a general examination and review of the person’s medical history, long-term and/or recent diabetes history, other medical history, family history of diabetes and/or cardiovascular disease, medication history and/or current medications. Social, cultural and lifestyle history should also be discussed.

Vascular risk factors, smoking status, weight and BMI should be assessed. Foot, eye and vision examinations should be undertaken and tests carried out for urine albumin excretion, urine protein on dipstick and serum creatinine. Psychological wellbeing should be assessed as well as attitudes to medication and self-care, immediate family and social relationships, and availability of informal support.

Treatment plans

Life-long insulin treatment is essential for type 1 diabetes. Treatment is individualised and includes a variety of insulin regimen options, which are taken at varying intervals. As type 1 diabetes is caused by destruction of the insulin producing cells, insulin therapy is a medical necessity. There are two components to insulin secretion. 

Firstly, basal insulin is the low and steady level of background insulin in the body. This insulin secretion is necessary to control the glucose that is continuously released from the liver, which is relatively constant, though typically declines slightly during the night and peaks before dawn. Secondly, meal-time bolus insulin is insulin secretion which sharply increases in response to glucose absorbed from food and drink. 

Insulin therapy aims to mimic the body’s natural process of producing basal and mealtime insulin, hence the need for continual administration.

It is important to maintain a target blood glucose level to minimise the risk of long-term complications. Adults with diabetes should aim for a target HbA1c level of 48mmol/mol (6.5%)¹ or lower. An individualised HbA1c target should be agreed with the person, taking into account factors such as their daily activities, aspirations, likelihood of complications, comorbidities, occupation and history of hypoglycaemia.

The main adverse effect of insulin treatment is hypoglycaemia which can range from mild to severe. Severe hypoglycaemia can result in loss of consciousness and coma. Someone with hypoglycaemia should be given oral glucose if they are able to swallow, or intramuscular glucagon if they are not conscious. People should be advised to test their blood glucose level at least four times a day, including before meals and before bed. More frequent testing may be required in certain circumstances, for example during periods of illness or if the target HbA1c level is not achieved. Self-monitoring skills should be reviewed at least annually, checking that the person knows how to use their blood glucose meter, when to test and how to interpret and respond to the results. 

Lifestyle advice 

People with diabetes should be given information on diet, including carbohydrate-counting training (a meal planning technique for managing blood glucose levels by matching carbohydrate quantities to insulin doses). Regular exercise (30 minutes, five times a week) may lower blood glucose levels and should be encouraged if appropriate. Exercise increases the amount of glucose used by the muscles for energy.

Alcohol may exacerbate or prolong the hypoglycaemic effect of insulin and signs of hypoglycaemia may become less clear, therefore people with diabetes should be advised to drink in moderation and avoid drinking alcohol on an empty stomach as the alcohol will be absorbed faster.

People with type 1 diabetes may wish to wear some form of diabetes identification to alert others to their condition in case of emergency. People who are diagnosed with type 1 diabetes should be offered a structured education programme to help them manage their condition, including self-monitoring of blood glucose, managing their insulin therapy, treatment targets and lifestyle management. They should receive an individual care plan which takes into account their wishes, circumstances and clinical findings. Information should also be provided on management of special situations (for example driving, fasting, pregnancy, illness and physical activity). Up-to-date information on support groups should be provided. For example Diabetes Ireland www.diabetes.ie

References

1. National Institute for Health and Care Excellence. Type 1 diabetes in adults: diagnosis and management NICE Guidelines [NG17]. Published August 2015, Available from: https://www.nice.org.uk/guidance/ng17 [Accessed April 07,2016] 
2. Diabetes Ireland. Available at www.diabetes.ie/about-us/diabetes-in-ireland/
3. National Institute for Health and Care Excellence. Diabetes (type 1 and type 2) in children and young people: diagnosis and management NICE Guidelines [NG18]. Published August 2015, Available from: https://www.nice.org.uk/guidance/ng18 [Accessed April 07,2016] 
4. Diabetes UK. Diabetes and genetics. Available from: http://www.diabetes.co.uk/diabetes-and-genetics.html [Accessed April 07,2016]
5. van Belle TL, Coppieters KT, von Herrath MG. Type 1 diabetes: etiology, immunology, and therapeutic strategies. Physiol Rev. 2011 Jan;91(1):79-118. Available from: http://physrev.physiology.org/content/91/1/79.long