Diabetes mellitus is a disease of disturbed carbohydrate metabolism, characterised by hyperglycaemia. An absolute or relative decrease of insulin secretion caused by the malfunctioning of the beta cells of the pancreas, and insulin resistance in liver, muscular and fatty cell tissue contribute to the development of type 2 diabetes mellitus (T2DM). These metabolic abnormalities may also contribute to the development of other clinical conditions, such as hypertension, dyslipidaemia and obesity. The pathogenesis is multifactorial, with genetic factors (impaired insulin secretion) and environmental factors (insulin resistance: overeating, sedentary lifestyle). Altogether, T2DM may lead to severe microvascular (neuropathy, retinopathy, nephropathy) and macrovascular (coronary heart disease, stroke) disease. This implies that patients with T2DM must be encouraged to adopt a healthy lifestyle aimed at not only reducing hyperglycaemia but also at the reduction of all risk factors for microand macrovascular disease. Moreover, the monitoring of, and, if necessary, treatment of their metabolic abnormalities is indicated.
Symptoms of diabetic hyperglycaemia may be thirst, polyuria and weight loss, although most patients do not experience these symptoms at the time T2DM is diagnosed. Hyperglycaemia is often noted during routine laboratory testing and a diagnosis is made with two fasting plasma glucose values ≥7.0 mmol/l taken on two different days. The diagnosis can also be made with one fasting plasma glucose value ≥7.0 mmol/l or one non-fasting plasma glucose value ≥11.1 mmol/l in combination with hyperglycaemic symptoms. Because not all patients with T2DM will develop symptoms or vascular complications, T2DM might be considered a risk factor instead of a disease in asymptomatic patients.
Pharmacologic treatment is needed in most cases to attain treatment goals, namely, the prevention and treatment of symptoms and complications, for example: (the progression of) cardiovascular disease, chronic renal insufficiency, retinopathy and neuropathy. Options have expanded to various medication categories, such as metformin, sulfonylureas (SU derivatives) and insulin, along with newer medication types such as SGLT2 inhibitors and GLP-1 receptor agonists. Our knowledge of diabetes and its treatment is constantly being developed with updates of treatment recommendations every few years. Treatment recommendations are increasingly personalised, with pharmacological options based on the patient’s risk of complications and comorbidity. As a result, diabetes management has become increasingly complex. Yet, in the Netherlands, it is mainly managed in primary care.
In Type 1 diabetes mellitus, the autoimmune destruction of beta cells causes absolute insulin deficiency. Type 1 diabetes generally presents with symptomatic hyperglycaemia in children or adolescents and, in 25%, as diabetic ketoacidosis. (Subtypes of) Type 1 diabetes may be diagnosed in adults. Type 1 diabetes is managed in secondary care.
Type 2 diabetes mellitus is recorded with the ICPC code T90. It should be distinguished from type 1 diabetes mellitus, which is classified as T89.
The incidence of type 2 diabetes mellitus is 1.8 per 1000 patient years, meaning two new diagnoses per 1000 patients in a year. The diagnosis is made mainly in older patients, with incidence numbers increasing from 45 years of age and with more new diagnoses in men than in women. Link/Figure 1
The prevalence of T2DM is 34.1 per 1000 patient years, meaning that among 1000 patients in a year, 34 have T2DM and seek help for it from their GP. Prevalence increases with increasing age. Among the elderly population (age 75+), over one fifth of the practice population is affected by T2DM. Prevalence is highest among men. This sex difference is most pronounced in the age group 65-75. Link/Figure 2
T2DM is ranked 11th of conditions with the highest prevalence as seen by FaMe-Net GPs; these are conditions for which a high proportion of the practice population seeks medical help over the course of one year. Link/Table 3 The high prevalence when compared to incidence indicates that T2DM is a chronic disease requiring the ongoing attention of the GP many years after the diagnosis has been made.
Type 1 diabetes has a prevalence of 3.2 per 1000 patient years. Link/Figure 4
T2DM initially presents asymptomatically in most patients. In FaMe-Net this is reflected in the table of Reasons for Encounter (RFEs) for T2DM. Link/Table 5 Most episodes start with a (request for) a blood test (*34), check (*31), test result (*60), as administrative contact (*62) or are initiated by the GP (*64). This means that the diagnosis is made after a patient requests some kind of screening, or as an (incidental) finding during another episode or as reported in a letter. Further, the diagnosis itself (T90) can be the RFE, which means that the patient thinks he or she has T2DM. This may be the case when the diagnosis has been suspected elsewhere, for example, in a (commercial) screening setting. When a sign or symptom is the RFE, excessive thirst (T01) and / or tiredness / weakness (A04) are reported.
Most patients diagnosed with T2DM receive health education / diet (*45), blood tests (*34) and prescriptions (*50) and a yearly medical examination (*31). Link/Table 6
Most common prescriptions in episodes of T2DM are biguanides (metformin), sulfonylureas (SU derivatives) and HMG COA reductase inhibitors (statins), followed by insulin. Link/Table 7 Note that this report shows only prescribed medication that was linked to this specific episode (T90 T2DM) during the course of a calendar year. In FaMe-Net, all prescribed medication must be linked to one episode, including in patients with multiple reasons (episodes) to prescribe. Medication that may also be prescribed for other episodes, such as statins or antihypertensives for ischaemic heart disease (K76), will be underreported here since they can be reported elsewhere.
Referrals to specialists and to other primary healthcare providers occur in a minority of T2D episodes. Specialist referrals concern mainly ophthalmologist referrals. Only a small percentage is referred to internal medicine on a yearly basis. Link/Table 8 Primary care referrals are mainly to dieticians and podiatry / podotherapy. Link/Table 9
Dutch guideline: https://richtlijnen.nhg.org/standaarden/diabetes-mellitus-type2#volledige-tekst (2023)
Robertson RP, Udler MS. Pathogenesis of type 2 diabetes mellitus. In: UpToDate, Nathan DM, Rubinow K (Eds), UpToDate, Waltham, MA, 2021
Wexler DJ, Udler MS. Initial management of hyperglycemia in adults with type 2 diabetes mellitus. In: UpToDate, Nathan DM, Rubinow K (Eds), UpToDate, Waltham, MA, 2021