Type 1 vs Type 2 Diabetes: Differences in Causes and Management
Type 1 diabetes is caused by autoimmune destruction of pancreatic β-cells leading to absolute insulin deficiency, while type 2 diabetes results from progressive loss of β-cell insulin secretion frequently on the background of insulin resistance. 1
Pathophysiological Differences
Type 1 Diabetes
- Results from autoimmune destruction of pancreatic β-cells, typically leading to absolute insulin deficiency 1
- Can be identified through the presence of islet autoantibodies (to insulin, glutamic acid decarboxylase, islet antigen 2, or zinc transporter 8) 1
- Follows a predictable progression through three distinct stages:
- Stage 1: Multiple autoantibodies with normoglycemia (presymptomatic)
- Stage 2: Autoantibodies with dysglycemia (presymptomatic)
- Stage 3: Overt hyperglycemia with clinical symptoms 1
- Accounts for approximately 5-10% of all diabetes cases 1
Type 2 Diabetes
- Caused by progressive loss of adequate β-cell insulin secretion frequently occurring with insulin resistance 1
- Strongly associated with obesity, physical inactivity, and metabolic syndrome 2
- Pathways to β-cell dysfunction include genetic predisposition, epigenetic changes, inflammation, and metabolic stress 1
- Insulin resistance is a primary feature, often preceding diagnosis by many years 2
Clinical Presentation Differences
Type 1 Diabetes
- Often presents with classic symptoms of polyuria, polydipsia, and unintentional weight loss 1
- Approximately one-third of children present with diabetic ketoacidosis (DKA) 1
- Traditionally associated with childhood onset, but can occur at any age 1
- More variable presentation in adults who may not exhibit all classic symptoms 1
Type 2 Diabetes
- Often presents with more gradual onset of symptoms 1
- May be asymptomatic and discovered during routine screening 1
- Traditionally associated with adult onset, but increasingly seen in children and adolescents, particularly those with obesity 1
- Occasionally presents with DKA, particularly in ethnic minorities 1
Diagnostic Considerations
The AABBCC approach can help distinguish between types:
- Age: <35 years suggests type 1
- Autoimmunity: Personal/family history of autoimmune disease suggests type 1
- Body habitus: BMI <25 kg/m² suggests type 1
- Background: Family history of type 1 diabetes
- Control: Inability to achieve glycemic goals on non-insulin therapies suggests type 1
- Comorbidities: Certain conditions or treatments may suggest type 1 1
Misdiagnosis is common (up to 40% of adults with new type 1 diabetes are initially misdiagnosed as having type 2) 1
Management Differences
Type 1 Diabetes Management
- Always requires insulin therapy for survival 3
- Typically follows a basal-bolus approach using multiple daily injections or insulin pump therapy 3
- Carbohydrate counting and insulin dose adjustment are essential skills 1
- Continuous glucose monitoring is increasingly important for management 1
- Risk of diabetic ketoacidosis is higher if insulin is omitted 1
Type 2 Diabetes Management
- Initial therapy often begins with lifestyle modifications and metformin 1
- May progress to include various oral medications, injectable GLP-1 receptor agonists, SGLT2 inhibitors, and eventually insulin as β-cell function declines 1
- Weight management is a cornerstone of therapy 1
- May be managed without insulin for many years or indefinitely in some cases 3
Complications and Prognosis
- Both types can lead to the same chronic complications (retinopathy, nephropathy, neuropathy, cardiovascular disease), though rates of progression may differ 1
- Hypoglycemia is a more common concern in type 1 diabetes due to absolute insulin dependence 3
- Intensive glycemic control can substantially decrease the development of microvascular complications in both types 3
Special Considerations
- The traditional paradigm of type 1 diabetes occurring only in children and type 2 only in adults is no longer accurate 1
- Some patients may have features of both types (sometimes called "type 1½" or "double diabetes") 4
- Genetic testing may be warranted when clinical features are atypical or suggest monogenic forms of diabetes (MODY) 1
- Environmental factors play a role in both types but differ: viral triggers in type 1 versus lifestyle factors in type 2 2