**3. Definition, clinical characteristics, and epidemiology of diabetes mellitus**

DM is a chronic metabolic disease characterized by hyperglycemia caused by a deficit of pancreas insulin production known as diabetes mellitus type 1 (DM1) or by insulin receptor dysfunction known as diabetes mellitus type 2 (DM2) [2]. DM is characterized by the presence of polyuria, polyphagia, and polydipsia. Patients present an unexplained weight loss; paresthesia of the extremities and foot pain may occur, as well as asthenia and recurrent or complicated infections. If the patients are not adequately treated, it can be associated with renal, visual, cardiac, intestinal, diabetic ketoacidosis, or diabetic coma complications, and it can lead to brain damage [8]. DM is currently considered a risk factor for the development of Alzheimer's disease (AD) and Parkinson's disease (PD) [3].

In recent years, the prevalence of this disease has increased in a progressive and alarming way, becoming a public health problem. The National Center for Chronic Disease Prevention and Health Promotion estimates that in 2017, 9.4% of the United States population suffers from diabetes, that is, 30.3 million people, of which 21.1 million people are diagnosed and 7.2 million people who have diabetes have not been diagnosed. On the other hand, the last report of the World Health Organization on the profiles of countries for diabetes in 2016 reports that in the United States, 3% of the population dies from this disease. **Table 2** highlights the figures on the number of deaths caused by this disease in the five countries with the highest number of patients according to the statistics portal Statista.


*\*Data according to WHO 2016*

*\*\*Data according to Statista 2017*

#### **Table 2.**

*Cases and deaths due to diabetes mellitus in the countries with the highest prevalence.*
