Diabetes mellitus is a disease of disturbed carbohydrate metabolism, characterised by hyperglycaemia. An absolute or relative impairment in insulin secretion, caused by disfunctioning 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 central obesity. The pathogenesis is multifactorial, with genetic influences (impaired insulin secretion) and ‘environmental’ contribution (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 have to be encouraged to adapt a healthy lifestyle aimed at not only reducing hyperglycaemia but reduction of all risk factors for micro- and macrovascular disease. Moreover, monitoring and if necessary treatment for their metabolic abnormalities is indicated.

Symptoms of diabetic hyperglycaemia may be thirst, polyuria and weight loss, although most patients present asymptomatic. The hyperglycaemia is often noted during routine laboratory testing. 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 patients to attain treatment goals. The options have expanded to multiple medication classes. The knowledge on diabetes and its treatment are heavily in development with updates of treatment recommendations every few years. It has made diabetes management increasingly complex, yet it is managed mostly in primary care in the Netherlands. 

In type 1 diabetes mellitus, an 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 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 almost 2 new diagnoses per 1000 patients in a year in the total FaMe-Net population. T2DM occurs mainly among older patients, with incidence numbers increasing from 45 years of age, and with higher numbers 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 seek help from their GP for T2DM. The prevalence increases with increasing age. Among the elderly population (age 75+), over one fifth of the practice populations is affected. T2DM is more common among men. This sex difference is most pronounced in the age group 65-75. Link/Figure 2 

T2DM is among the top twenty 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 during a year. Link/Table 3 

Type 1 diabetes has a prevalence of 3.2 per 1000 patient years (Link/Figure 4).

T2DM initially presents asymptomatic 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, check, test result, or as administrative contact. This means that the diagnosis is made after a patient requests for some kind of screening, or as (incidental) finding in another episode or reported in a letter. Further, the diagnosis itself (ICPC 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 or tiredness/weakness are reported.

Most patients diagnosed with T2DM have yearly medical examination, health education / diet, blood tests and prescriptions. Link/Table 6

Most common prescriptions in episodes of T2DM were 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 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 occurred in a minority of T2D episodes. Specialist referrals concerned mainly ophthalmologist referrals. Only a small percentage was referred to internal medicine on a yearly base. Link/Table 7 Primary care referrals were mainly to dieticians, and also to podiatry/podotherapy. Link/Table 8