The largest incidence of DM1 occurs between ages 10 to 15, and it is similar for both genders. The incidence and prevalence of DM2 increases prominently with age, particularly after age 40, being more frequent in women than men.

DM1 is more frequent in the population of Caucasian origin than other ethnic groups. But DM2 is more prevalent in other ethnic groups than in the Caucasian population.

Obesity is not associated with the development of DM1, but it is an important risk factor for DM2 (3 times as much), as well as for gestational diabetes (twice as much).

Sedentariness is not related with the appearance of DM1. Inactivity reduces glucose tolerance, and physical exercise improves it. Since sedentariness favors obesity, which by itself is an important DM2 risk factor, physical exercise can reduce the risk of developing this kind of diabetes.

Women that present gestational diabetes are at a high risk of developing diabetes later on. Prospective studies show that 60% of women with gestational diabetes progressed to diabetes within a period of 16 years.

Environmental factors could play an important role in the genesis of type 1 diabetes. It has been observed, in several countries, a seasonal variation of its incidence. A few observations suggest that an environmental factor such as a virus (measles, rubella, mumps, coxsackie B4) or an immune response to an environmental factor might cause DM1 in genetically susceptible individuals.

Individuals that have certain genetic markers (some genes from the HLA system) present a risk of developing DM1 four to nine times higher than those who do not have them. However, familial recurrence is not common for this type of diabetes. But first-degree family members of individuals with DM2 have a two to six times higher chance of developing diabetes than people with no family history, with the same age.