## Epidemiology of Diabetes Mellitus **Key Point:** Type 2 diabetes mellitus (T2DM) accounts for approximately 85–90% of all diabetes cases globally and in India, making it the most common form of diabetes. ### Prevalence Data | Type | Global Prevalence | Pathophysiology | Age of Onset | | --- | --- | --- | --- | | Type 2 DM | 85–90% | Insulin resistance + relative β-cell dysfunction | Usually >30 years | | Type 1 DM | 5–10% | Autoimmune β-cell destruction | Usually <30 years | | Gestational DM | 3–5% (in pregnancy) | Insulin resistance in pregnancy | During pregnancy | | Secondary DM | <2% | Pancreatic disease, endocrinopathy, drugs | Variable | **High-Yield:** In India, T2DM prevalence is rising dramatically due to urbanization, sedentary lifestyle, and obesity. The Indian Council of Medical Research (ICMR) estimates >70 million people with T2DM in India. ### Why Type 2 DM is Most Common 1. **Genetic predisposition** — polygenic inheritance with >100 susceptibility loci identified 2. **Environmental factors** — obesity, sedentary lifestyle, high-calorie diet (major modifiable risk factors) 3. **Insulin resistance** — develops gradually over years, allowing late diagnosis 4. **Age-related decline** — β-cell function declines with age, increasing incidence in older populations **Clinical Pearl:** Type 2 DM is often asymptomatic in early stages, leading to delayed diagnosis. Many patients are diagnosed incidentally on screening or when complications appear. **Mnemonic — RISE of T2DM:** Resistance (insulin), Insulin secretion (relative ↓), Sedentary lifestyle, Environmental factors.
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