**5. Definition and epidemiology of dementias**

Dementia is a syndrome of generalized deterioration, since it involves cognitivebehavioral damage; is acquired, degenerative in most cases, and multi-etiological; and will have repercussions on the family, work, and social life of the person. Dementia is also characterized by a decrease in mental faculties of the individual, and clinical characteristics may vary depending on the neuropathological process of the disease and even the specific characteristics of each person. Symptoms may include short-term memory loss, temporary and spatial disorientation, and difficulty in communication and behavior alterations [20]. The most frequent types of dementia include vascular dementia, AD, and PD, although there are other forms of dementia such as frontotemporal dementia and dementia caused by Lewy body deposits. It usually affects older adults; however, it is not the result of normal aging.

Currently dementia is not considered a social priority in most countries, despite the increase in incidence. It is estimated that there are at least 50 million people in the world suffering from dementia, with 10 million new cases registered every year. WHO statistics indicates that it is expected that by the year 2030 and 2050, the figures will, respectively, increase to 76 million and 145 million cases. AD is the main cause of dementia, representing at least 60% of cases, with a prevalence of 10–30% in the population over 65 years of age [21–23]. On the other hand, PD is the second most common neurodegenerative disease after AD which frequently goes through a process of dementia. PD has a prevalence between 100 and 300/100,000 of the population [24], and it is expected that by 2030 the number of patients duplicates [25–27].

These numbers are alarming, and they represent a really serious situation that has not been given the attention and follow-up that is required, because as

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**Figure 1.**

*Diabetes Mellitus and Amyloid Beta Protein Pathology in Dementia*

**6. Diabetes mellitus as a risk factor for dementias**

factor for dementia, especially DM2, which is also related to obesity.

already mentioned, it has not been a social priority for most countries yet has a

Dementia is a complex disorder of multifactorial etiology that results in alterations in health status changes in lifestyle. It is important to identify the risk factors, at an early age, to prevent this disease. There are several factors related to dementia such as age [28], ethnic group [29], gender [30], genetic factors [31], physical activity [32], smoking, alcoholism [33], education level [34], environmental factors, and obesity [35, 36]. In addition, in the last decade, DM has been associated as a risk

Damage to cognitive functions has been observed in patients with DM2 compared to healthy patients [37, 38]. Individuals with DM2 present alterations in their attention capacity, execution, processing speed, work memory, and verbal memory [39, 40]. Studies report a reduction of the gray matter in the frontotemporal cortex, as well as the decrease in glucose metabolism in patients with alterations in executive and memory functions [41], but it also has been associated to a white matter reduction [38]. On the other hand, the damages in verbal memory correlate with the integrity of the parahippocampal gyrus [42]. In other words, DM2 represents an important risk factor for dementia. Interestingly, in the five main countries with a high DM prevalence (see **Table 2**), there is also a significant prevalence of dementia (**Figure 1**). DM2 is the most common type of diabetes in which autoimmune antibodies appear to be the cause. In this type of diabetes, insulin resistance is observed, which limits the ability to respond to hormones, both endogenous and exogenous [43]. In some cases, insulin resistance is a result of a lower number or a mutation of insulin receptors (IR). These receptors are expressed in the central nervous system (CNS), in the hypothalamus, olfactory bulb, cerebral cortex, cerebellum, and hippocampus [44–46]. Insulin can cross the blood-brain barrier and reach its target, generating anorexic effects by activating the satiety center. This happens because insulin and the insulin-like growth factor-1 (IGF-1) activate PI3K causing the opening of

which causes it to disrupt its activity, and thus, it stimulates the secretion of the

*Dementia prevalence in the five countries with the highest diabetes mellitus prevalence in 2017. DM, diabetes* 

ATP), thus hyperpolarizing the neuron

*DOI: http://dx.doi.org/10.5772/intechopen.84473*

ATP-dependent potassium channels (ChK\*

*mellitus (thousands); Dem, dementia (for every 1000).*

great economic impact.

*Amyloid Diseases*

**4. Amyloidosis' association with diabetes mellitus**

**5. Definition and epidemiology of dementias**

Case studies have shown a deep connection in patients who suffer from amyloidosis and type 2 diabetes, especially in those with pancreatic damage [9, 10]. Studies have focused on a neuro pancreatic hormone called islet amyloid polypeptide (IAPP) or amylin, secreted along with insulin by β pancreatic cells, and its possible etiology in type 2 diabetes [11]. IAPP functions as a glucose homeostatic regulator, but once it suffers synthetic alterations, it starts to accumulate inside and outside the pancreatic cells resulting in apoptosis [12]. Although the specific etiology has remained unknown, there have been many hypotheses on what causes these pancreatic amyloid deposits. One of the most accepted hypotheses consists of a malfunctioning β pancreatic cell which is unable to correctly process amylin, resulting in the installment of amyloid proteins inside and outside the cells [13]. Another accepted theory indicates the genetic overexpression of amylin, which causes amyloid deposits, although there has not been a proven correlation (in humans) between high IAPP circulating levels and glucose intolerance [14]. It has been proved that the amino acids within the 26–29 sequence are a determinant factor proved in the development of amyloid deposits only in humans, simians, and felines, which are presumed to be the only three species to suffer from an amyloid deposit diabetes [9, 10, 15, 16]. It has been proved that in 9% of the diabetic population, there has been an identified mutation within the promoter region in the amyloid gene, increasing its transcription [17–19]. For years it has been proven that high blood glucose is not only toxic to β pancreatic cells, but it also generates an overexpression on the IAPP gene which contributes to pancreatic amyloid deposits, inducting cellular apoptosis [12]. It was never clear whether IAPP was the cause or the consequence of diabetes, but once the genetic mutation in the promoter region was finally identified, there is still more research to be done in order to be completely certain.

Dementia is a syndrome of generalized deterioration, since it involves cognitivebehavioral damage; is acquired, degenerative in most cases, and multi-etiological; and will have repercussions on the family, work, and social life of the person. Dementia is also characterized by a decrease in mental faculties of the individual, and clinical characteristics may vary depending on the neuropathological process of the disease and even the specific characteristics of each person. Symptoms may include short-term memory loss, temporary and spatial disorientation, and difficulty in communication and behavior alterations [20]. The most frequent types of dementia include vascular dementia, AD, and PD, although there are other forms of dementia such as frontotemporal dementia and dementia caused by Lewy body deposits. It usually affects older adults; however, it is not the result of normal aging. Currently dementia is not considered a social priority in most countries, despite the increase in incidence. It is estimated that there are at least 50 million people in the world suffering from dementia, with 10 million new cases registered every year. WHO statistics indicates that it is expected that by the year 2030 and 2050, the figures will, respectively, increase to 76 million and 145 million cases. AD is the main cause of dementia, representing at least 60% of cases, with a prevalence of 10–30% in the population over 65 years of age [21–23]. On the other hand, PD is the second most common neurodegenerative disease after AD which frequently goes through a process of dementia. PD has a prevalence between 100 and 300/100,000 of the population [24], and it is expected that by 2030 the number of patients duplicates [25–27]. These numbers are alarming, and they represent a really serious situation that has not been given the attention and follow-up that is required, because as

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already mentioned, it has not been a social priority for most countries yet has a great economic impact.
