Diabetes

Increased blood glucose concentration in diabetes causes damage to almost every organ

There are two less common types of diabetes. Diabetes resulting from specific genetic conditions or genetic defects, surgery, drugs, malnutrition, infections, and other illnesses is sometimes referred to as type 3 diabetes. This type of diabetes accounts for 1% to 5% of all diagnosed cases. Gestational diabetes mellitus (GDM) sometimes develops during pregnancy but usually disappears after delivery. The ICD-10 classifies type 1, type 2 and type 3 diabetes under E10-E14. GDM is classified under O24.4.

A complex set of symptoms leads to the diagnosis of diabetes

Common symptoms of diabetes mellitus are excessive thirst, increased urine elimination, fatigue, genital itching or regular episodes of thrush, slow healing of wounds and sudden weight loss. In severe cases, diabetes can lead to unconsciousness, coma and death. The diagnosis of diabetes mellitus can be confirmed through a plasma or blood glucose test, measuring either fasting glucose, or glucose concentrations 2 hours after a glucose load (oral glucose tolerance test).

WHO diagnostic criteria for diabetes mellitus or its preliminary stages (IGT and IFG)

A separate EUphocus on 'Diabetes prevention and care' presents data from the EUCID project.

The EUphocus Diabetes prevention and care presents a selection of data collected by the EUCID project (European Core Indicators on Diabetes; data collection for 2004-2006). These include data from the general population on incidence, prevalence and mortality, data on risk factors in the diabetics population, as well as data on the complications of diabetes.

Substantial differences in diabetes prevalence among countries

The best way to estimate diabetes prevalence is the oral glucose tolerance test (OGTT). OGTT will detect irregularities in sugar metabolism in both individuals with previously diagnosed type 1 and type 2 diabetes, and those who do not know they have the disease. These data are usually collected in special (often regional) surveys and not by routine monitoring. According to this criterion, an estimated 8.6% of the adult (20-79 years) EU-27 population has diabetes, and country estimates range from 4.0% in the United Kingdom to 11.8% in Germany (IDF, 2006b); see Prevalence of diabetes in 2007 and estimates for 2025.

Data presented in Prevalence of diabetes mellitus in some EU countries are standardised according to the standard European population (Doll & Cook, 1967). This enables better comparisons among countries. The age-standardised prevalence of previously diagnosed and newly diagnosed diabetes together for the age group 30-64 years, ranges from 4.9% in Swedish men to 8.7% in English men. For women, it ranges from 4.0% in Italy to 7.2% in Spain. Among people between 65-74 years, the age-standardised prevalence is higher and ranges from 11.4% in Polish men to 22.6% in German men and from 13.1% in English women to 27.7% in Spanish women. The presented data are calculated from data given by the DECODE comparative study and a few additional recent surveys (DECODE Study Group, 2003; Rathmann et al., 2003; Glümer et al., 2003, ERGO-study). The IDF and the DECODE study rely (for the majority) on the same cohort studies. However, the numbers presented are different because different WHO diagnostic criteria were used and because IDF data are standardised according to the standard world population (see remarks under the presented table and figure for further explanation).

The prevalence of diabetes known to general practitioners (GPs) in different European countries shows less variation. For all ages, the prevalence known to GPs ranged from 1.6% in Slovenian men and women, to 3.1% in Belgian men and 3.4% in Belgian women (Fleming et al., 2004). These numbers are lower than the prevalence in the DECODE Study and theIDF database because the percentage of undiagnosed diabetes patients is not included.

Prevalence increases with age

Diabetes prevalence clearly increases with age (see Prevalence of diabetes mellitus in some EU countries). This increase is mainly due to the increase in type 2 diabetes. Of all diabetes patients, 90% have type 2 diabetes (WHO, 2006a; IDF, 2006b). Type 1 diabetes used to be the most frequent type of diabetes among children. However, type 2 diabetes is increasingly seen among children and adolescents as well (WHO, 2006a; IDF, 2006b).

Higher prevalence among lower socio-economic groups

Diabetes shows higher prevalence among lower socio-economic groups (with education as socio-economic indicator) as compared to higher socio-economic groups. The differences in diabetes prevalence between socio-economic groups are larger in women than in men. In men, the majority of countries show only small differences, while in women the association between the socio-economic position and diabetes prevalence is more clear. Both in men and in women differences are more accentuated in Western countries (Dalstra et al., 2005; Eurothine, 2007).

See also: EUphocus: Health inequalities.

No sex differences in diabetes prevalence

There is no clear sex difference in the overall diabetes prevalence. In most of the study cohorts of the DECODE study, the prevalence of previously undiagnosed diabetes, defined by isolated 2 hour post load hyperglycemia was higher in women. In contrast, the prevalence of undiagnosed diabetes defined by isolated fasting hyperglycemia was higher in men. The prevalence of known diabetes did not differ between men and women, except in people older than 80 years (DECODE Study Group, 2003).

Diabetes prevalence is expected to increase

Although increases in diabetes have already occurred globally, they have been especially dramatic in developing countries (WHO, 2003b; Passa, 2002).

The absolute number of people with diabetes in the EU-27 is estimated to rise even further, from approximately 31 million in 2007 to 37 million in 2025. That implies a rise from 8.6% to 10.2% of the total population. These figures are based on current age and gender specific prevalence rates. It is likely that age-specific prevalence rates will rise due to the increasing frequency of obesity (IDF, 2006a). These projections thus probably underestimate the factual 2025 prevalence.

More recent data expected to be available in 2007

By the end of 2007 more recent diabetes prevalence data will become available from the EUCID project. This project will make available national facts of diabetes mellitus and its risk factors from different EU-countries. The indicators for the EUCID project were established by the European Diabetes Indicators Project (EUDIP). Prevalence data will be collected retrospectively for the year 2005.

Comparison of mortality data should be interpreted with caution

Based on data on causes of death obtained from death certificates, about 103,000 persons have died from diabetes mellitus in the EU-27 in 2004 (Eurostat, 2007). Although more women than men died from diabetes (61,000 women and 44,000 men) standardised death rates (SDR) are higher for men (see Mortality from diabetes in 2003). Data based on registered primary causes of death seriously underestimate the actual number of deaths for which diabetes was a contributing factor (Roglic et al., 2005). As many diabetes patients die of cardiovascular disease, it is usually the cardiovascular disease that is recorded as the primary cause of death. Furthermore, methods of registration differ between countries and this affects the comparability of data. Therefore, the mortality data for diabetes and their international comparisons should be interpreted with some caution.

Changes in registration can influence mortality trends

There is no clear trend in the standardised death rates (SDR) for diabetes in EU countries since 1970 (WHO-HFA, 2006). A few countries showed some increase since 1980 (Portugal, Denmark). Austria showed a remarkable increase since 2000. On the other hand Belgium, Finland, Greece and the Czech Republic report some decrease since 1970. We mentioned already, however, that mortality data should be interpreted with caution. Changes in registration or attention for diabetes as primary cause of death could influence trends.

Diabetes complications cause major loss of quality of life

Patients with type 2 diabetes have moderately lower health-related quality of life scores than the general population of a similar age. This may be due to psychological effects associated with reduced general well-being, as well as effects on family relationships and social life. Furthermore, diabetics with complications have a lower quality of life than diabetics without complications. Loss of quality of life due to complications varies from sexual dysfunction, limb amputation and blindness, to the need for chronic kidney dialysis or kidney transplantation. Treatment with insulin is also associated with a lower quality of life (Koopmanschap, 2002).

Macrovascular complications include heart disease and diabetic foot

Cardiovascular disease (CVD) is the major complication of diabetes affecting larger blood vessels. 50% of people with diabetes die of cardiovascular disease, primarily heart disease and stroke (WHO, 2006a). The most important cardiovascular complications of diabetes are (WHO, 1999b; WHO, 2002e; WHO, 2003b;IDF, 2006a; EUDIP group, 2002):

• coronary heart disease (CHD) and cerebrovascular accident (CVA, including stroke): they occur when blood vessels are narrowed or blocked by fatty deposits (atheroslerotic plaques). High blood glucose levels promote atherogenesis and thrombosis through a range of biochemical pathways (Laakso, 1999).
• peripheral vascular disease (PVD, diabetic foot disease): in diabetic foot disease damage to blood vessels and nerves (see also diabetic neuropathy) causes ulcerations and infection which can necessitate amputation. Between 1 and 4% of the diabetic patients in Europe has to undergo amputation (IDF, 2006a).

Microvascular complications affect eye, kidney and nervous system

Complications of diabetes affecting the small blood vessels (WHO, 1999b; WHO, 2002e; WHO, 2003b; WHO, 2006a; IDF, 2006a; EUDIP group, 2002 )are:

• diabetic retinopathy: eye disease due to the damage of small blood vessels in the retina. After 20 years of diabetes almost all patients with diabetes type 1 and more than 60% of patients with diabetes type 2 are affected to some degree (EUDIP group, 2002). It can lead to severe visual disability and blindness. This affects 10 and 2% of patients respectively after 15 years of diabetes (WHO, 2002e).
• diabetic nephropathy: kidney disease and kidney failure may lead to chronic renal dialysis or kidney transplantation. About 10-20% of people with diabetes die of kidney failure (WHO, 2006a). According to the WHO guidelines an increase of serum creatinine ≥ 400 μmol/ll is considered as end stage renal failure where dialysis is imminent (EUDIP group, 2002).
• diabetic neuropathy: neuropathy can lead to sensory loss and damage to the limbs, increasing risk of foot ulcers (and ultimately amputation) and causing autonomic dysfunction, including sexual dysfunction (WHO, 1999b). Up to 50% of people with diabetes are affected (WHO, 2006a).

Certain risk factors increase risk of complications

Poor metabolic control (manifesting itself in hyperglycaemia) increases the risk for micro and macro vascular complications. Glycosylated haemoglobin (HbA1c) reflects metabolic control over the past 2-3 months with chronically high blood sugar levels resulting in an increased HbA1c. Above 7.5% the risk for complications is increased. Approximately half of diabetics have HbA1c above 7.5% (EUDIP group, 2002). Other risk factors for complications are: abnormal concentrations of total cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides and presence of microalbuminuria, hypertension, smoking, overweight and obesity (EUDIP group, 2002).

Diabetes contributes to 1.6 - 6.6 % of total health care costs

The CODE-2 study has measured the health care costs of people with type 2 diabetes in 8 EU countries: Belgium, France, Germany, Italy, the Netherlands, Spain, Sweden and the UK (Jönsson, 2002). For these 8 countries the average annual costs per patient with type 2 diabetes were estimated at €2,834 in 1999. The health care costs of diabetes as a percentage of the total healthcare expenditures ranged from 1.6% in the Netherlands to 6.6 % in Italy. Hospitalisations accounted for the greatest proportion of costs (55%).

A Swedish study (Jonsson et al., 2000) observed that the cost profile during the natural history of diabetes is 'U' or 'J' shaped with relatively high costs immediately after diagnosis, followed by a fall and again a rise with the onset of complications (Jonsson et al., 2000). Indirect costs by diabetes due to loss of productivity may be as great or even greater than direct health care costs (WHO, 2002f).

Diabetes is among the leading causes of death and disability

In the WHO European Region diabetes accounts for an estimated 2.2 million DALYs in 2002. Diabetes ranked among the ten leading causes for the loss of healthy life years, expressed in DALYs, in Cyprus, Denmark, Greece, Italy, Malta and Portugal (WHO, 2005f).

Overweight and obesity are the most important risk factors for diabetes

Risk factors for diabetes can be divided in 'biological and personal factors' and 'health behaviours'.

Biological and personal factors (WHO, 2003b; IDF, 2006a; Baan et al., 2005):

• Overweight and obesity, especially central obesity (accumulation of fat around the waist), are the strongest risk factors for diabetes mellitus. In the Netherlands, for example, the population attributable risk (PAR) of being overweight and obese, for diabetes incidence, is 66%. This means that 66% of new diabetes cases are attributable to overweight (28%) or obesity (38%) (Baan et al., 2005).
• Certain genes are associated with higher risk of developing diabetes. This genetic predisposition is more important for the type 2 than for the type 1 diabetes. However, diabetes is a multifactorial disease: genes alone are not enough, environmental factors are needed to trigger the onset of disease.
• GDM (gestational diabetes mellitus): children of mothers with diabetes are at a higher risk of developing type 2 diabetes. Breastfeeding has a protective effect for children of both, diabetic and non-diabetic women.
• Prediabetes, including people with Impaired Glucose Tolerance (IGT) and Impaired Fasting Glucose (IFG) have blood glucose concentrations above the normal range, but below the diagnostic criteria for diabetes. IGT and IFG are called pre-diabetes but they are also a risk factor for developing diabetes.

Health behaviours (WHO, 2003b; IDF, 2006a; Baan et al., 2005):

• Sedentary lifestyle favours the development of diabetes type 2, while physical activity significantly reduces the risk.
• Dietary factors:
• A diet high in fat and saturated fatty acids is associated with a higher risk of impaired glucose tolerance, higher fasting glucose concentrations and higher insulin levels.
• A high intake of dietary fibre (non-starch polysaccharides) from wholegrain cereals, vegetables and fruits protects against the development of diabetes.
• Smoking increases the risk of developing diabetes.

Risk factors interact

All of these risk factors operate in complex interaction, e.g. health behaviours interact with genetic predisposition to result in overweight, which in turn may lead to diabetes. Often a combination of environmental risk factors is present in one individual.

Strength of evidence on lifestyle factors and risk of developing type 2 diabetes

Lifestyle changes can prevent the onset of type 2 diabetes

Lifestyle changes may prevent the onset of type 2 diabetes mellitus in persons with a higher risk of developing the disease (primary prevention). Examples are reducing the intake of total fat and saturated fat, increasing the intake of fibre and increasing physical activity, as well as losing excessive weight. Evidence for the preventive effect of lifestyle changes comes from several intervention studies, such as the 'Diabetes Prevention Program' in the United States and the Finnish 'Diabetes Prevention Study' (Knowler et al., 2002; Tuomilehto et al., 2001).

The objective of the EU co-funded project Diabetes in Europe is to implement and evaluate a lifestyle intervention programme in different European countries to prevent type 2 diabetes in high-risk individuals. The project started in spring 2005 and has a duration of 3 years.

Screening helps in early detection and prevention of complications

As many people are unaware of their diabetes, they often start to show evidence of organ or tissue damage before diabetes is diagnosed and treated. Screening is aimed at early detection and hence at earlier treatment of previously undiagnosed type 2 diabetes to prevent development of complications (secondary prevention). However, evidence from randomized controlled trials on the effectiveness of screening is insufficient (WHO, 2003c). The overall aims of the ADDITION study in the UK, Denmark and the Netherlands are to evaluate whether screening for prevalent undiagnosed type 2 diabetes is feasible, and whether subsequent intensive treatment of diabetes and associated risk factors, is feasible and beneficial. This study does not answer the question whether screening is effective or not, because a control group is lacking (Lauritzen et al., 2000).

Prevention of complications by regulating blood glucose concentration

The primary aim of diabetes treatment is to regulate glucose concentration in the blood and prevent micro- and macrovascular complications that are caused by raised blood glucose levels (tertiary prevention). Intervention trials such as the United Kingdom Prospective Diabetes Study have shown that the combined treatment of hyperglycaemia, hypertension and hyperlipidemia is more effective in reducing the risk for macrovascular complications than treating hyperglycaemia alone (UKPDS-group, 1998a; UKPDS-group, 1998b). Hyperglycaemia in type 1 diabetes is treated by injections of insulin and a healthy diet. Hyperglycaemia in type 2 diabetes is treated by a healthy diet and oral antidiabetics. Some people with type 2 diabetes also need insulin injections.

Preventive care practices counteract worsening of complications

Preventive care practices can counteract worsening of complications. Examples are laser therapy for diabetic eye disease, foot care programs for diabetic feet and blood pressure lowering drugs to treat diabetic kidney disease (CDC, 2005c).

A new WHO review on the Prevention of diabetes and its complications will be available in the second half of 2008.

Summary of strength of evidence on lifestyle factors and risk of developing type 2 diabetes (WHO, 2003b)

Diagnostic criteria for Impaired Glucose Tolerance (IGT), Impaired Fasting Glucose (IFG) and diabetes mellitus according to WHO (WHO, 1999b, WHO/IDF, 2006)

Disease-specific mortality

Breastfeeding

Life expectancy

Healthy life expectancy

Children's Health and the Environment

Diabetes prevention and care

Alcohol use

Alcohol policies

Overweight

Smoking

Smoking policies

Health Inequalities

Eurostat, Statistical Office of the European Communities

HFA-DB WHO Health for all database

Diabetes atlas

Health-EU Portal, other non-communicable diseases

WHO diabetes programme

IDF International Diabetes Federation

IDI International Diabetes Institute

Health Information from primary care (Phase 2)

Diabetes Conference, EU conference on prevention of Type 2 diabetes

EUCID EUropean Core Indicators in Diabetes

EUROCISS European Cardiovascular Indicators Surveillance Set

EU-project: Diabetes in Europe Prevention using Lifestyle, Physical Activity and Nutritional intervention

IMAGE Development and Implementation of a European Guideline and Training Standards for Diabetes prevention

EHRM European Health Risk Monitoring Project

Prevalence of diabetes in 2007 and estimates for 2025, in Iceland, Norway, Switzerland and the EU-27

Mortality (SDR) for diabetes for all ages, male, female and total, in Iceland, Norway, Switzerland and the