Type 2 diabetes does not develop at random. Several recognised risk factors make it more likely, and they differ between adults and children and adolescents. The same factors decide when testing for the disease should begin, so they also mark the people in whom screening is worthwhile.
Risk factors in adults
In adults the recognised risk factors are these:
- Physical inactivity
- A first-degree relative with diabetes
- High-risk race or ethnicity (for example African American, Latino, Native American, Asian American, Pacific Islander)
- A woman who delivered a baby weighing more than 9 lb, or who was diagnosed with gestational diabetes
- Hypertension (≥130/80 mm Hg, or on treatment for hypertension)
- HDL cholesterol below 35 mg/dL (0.90 mmol/L) and/or a triglyceride level above 250 mg/dL (2.8 mmol/L)
- Polycystic ovary syndrome
- Prediabetes (HbA1c ≥5.7%, impaired glucose tolerance, or impaired fasting glucose)
- Other conditions associated with insulin resistance (for example severe obesity, acanthosis nigricans — velvety dark thickening of the skin in body folds — or metabolic dysfunction-associated steatotic liver disease)
- A history of cardiovascular disease
- Other high-risk groups (HIV infection, exposure to high-risk medicines, periodontal disease, or a history of pancreatitis)
Obesity and physical inactivity are the modifiable factors that matter most, and both raise risk mainly by increasing insulin resistance, the reduced response of tissues to insulin. The metabolic consequences of insulin resistance travel together: hypertension, a low HDL and high triglyceride pattern, and cardiovascular disease often appear in the same person, which is why they sit beside each other in this list.
Risk factors in children and adolescents
In children and adolescents the risk factors are fewer and are grouped by their source:
- Family history: type 2 diabetes in a first- or second-degree relative
- Race and ethnicity: Native American, African American, Latino, Asian American or Pacific Islander
- Signs of insulin resistance: acanthosis nigricans, hypertension, dyslipidemia, small-for-gestational-age birth weight, or polycystic ovary syndrome
- Maternal history: diabetes or gestational diabetes during the child’s gestation
Environmental factors
Beyond the individual characteristics above, two environmental influences take part in the pathogenesis of type 2 diabetes.
The first is the balance between physical activity and calorie intake: when intake consistently exceeds expenditure, the surplus is stored as fat, and expanding adipose tissue promotes insulin resistance. The second is ambient temperature, which sets how much energy the body spends producing heat. Energy expenditure is higher in a cool environment and lower in a warm one, so rising indoor temperatures have been proposed as one contributor to weight gain; the size of that contribution is uncertain, and it is only one influence among many.