**2.1 Relationship of cognitive function with type 2 DM**

Cognitive impairment is a type of disorder which has not been studied and explored as the complications of DM. At the same time, the association of DM with cognition is well acknowledged. The meta-analysis shows small to moderate performance decline in persons with diabetes relative to nondiabetic controls in each domain examined. The motor function is largely affected, while attention/concentration is affected minimally [19]. Another study shows that people with type 2 DM will have higher rate of cognitive impairment than people that do not have DM [20]. Besides that, the effect of diabetes on the normal mental functions is often disregarded. This may be due to lack of signs and standard assessment technique to measure the cognitive function of the diabetes patient [21]. Hyperglycaemia which is common in people with diabetes has been associated with an increase in the possibility of developing Alzheimer's disease and vascular dementia in both the general public and people with cognitive impairment [22]. It has been estimated that an individual with DM is 1.5 times more likely to experience cognitive dysfunction and dementia than a normal healthy individual [23].

Elderly people who are more than 65-year-old will have more than 20% chances to be diagnosed with both DM and impaired cognitive function [24]. Type 2 DM has been associated with few cognitive impairments such as decreases in

**63**

*Cognitive Dysfunction in Diabetes Mellitus DOI: http://dx.doi.org/10.5772/intechopen.85940*

**2.2 Duration of DM and cognitive impairment**

**2.3 Influence of age and cognitive impairment**

and others [25].

increases [28].

psychomotor speed, processing speed, visual retention, attention, concentration and many more. It is understood that more significantly hyperglycaemia, vascular disease, hypoglycaemia and insulin resistance affect cognitive decline, but the exact pathophysiological mechanisms not of cognitive decline in diabetes are unclear [3]. The causes of cognitive decline in diabetes may be the direct effect of the chronic hyperglycaemia on the brain regions, blood lipid, blood pressure, hypoglycaemia

Several studies have studied about the linkage of DM with cognitive decline in elderly population. A perspective (over 20 years) cohort study in the USA with mid-age (mean age 58) diabetic patient reported that DM in the midlife was related to a significant increase in cognitive impairment. This study included 13,351 black and white adults aged 48–67 years old, and their cognitive function was examined using three cognitive tests, which are the delayed-word-recall test (DWRT), the digit substitution test (DSST) of Wechsler Adult Intelligence Scale-Revised (WAIS-R) and the word fluency test (WFT). The study also reported that a patient with poorly controlled DM might have bigger cognitive disorder than well-controlled ones and longer duration of DM will have increased chances of late-life cognitive disorder [26]. A cross-sectional study was conducted on 57 patients having type 2 DM. The result shows that patients with type 2 DM had low grades in the cognitive testing and poor performance in different cognitive function tasks which include the verbal relations, visual reasoning, short-term memory test and many more. Cognitive function is impaired more with the untreated DM patient than the treated group [25]. Cognitive dysfunction is nonlinearly related to the duration of diabetes. However, cognitive decline is more prominent when the duration of DM is more than 5 years and presence of hypertension which further increases the risk of cognitive impairment [21]. The patients having diabetes showed poor performance in the tests of recent memory, repetition and attention, as compared to the control group and DM, and the people with long history of DM are more at risk of cognitive decline [27]. It is concluded that cognitive function of diabetes type 2 patients should frequently be tested. This is because the duration of disease can be related with the decrease in cognitive function. As duration increases, impairment also

A prospective study is done to observe and determine the impact of DM on the cognitive function impairment in the oldest of the old participants. The study was conducted using prospective population method. They have chosen approximately 599 participants with the respond rate of 87% with the age ranges from 85 to

90 years old. The memory function test does not show any differences between both diabetic and nondiabetic participants. Cognitive function of diabetic participants is

The results of another research show that diabetic patients more than 65 years old have higher chances to be associated with impaired cognitive function [24]. Besides that, one more study was conducted that is related to assessing the status of cognitive function in people that have DM. The chosen patients were assessed by using MMSE and 3MS (the modified mini-mental state examination). The scores for both assessments were 30 and 100, respectively. At the same time, the relationships of age, gender and duration of diabetes and HbA1c among the DM with 3MS will also be assessed. The results of this study were diabetic patients have lower

affected when the time and speed test has been conducted [29].

*Type 2 Diabetes - From Pathophysiology to Modern Management*

**1.1 Global and Malaysian scenario of type 2 DM**

was 1260 people compared to 1070 for males [13].

**2.1 Relationship of cognitive function with type 2 DM**

dementia than a normal healthy individual [23].

**2. Cognitive function**

countries [12].

Type 1 DM is common in children, teenager as well as young adult [10]. DM can lead to complications such as diabetic nephropathy, diabetic retinopathy, ischaemic heart disease and many more [11]. The number of people with type 2 DM is increasing in every country with 79% of people with DM living in low- and middle-income

Some 425 million people worldwide, or 8.8% of adults, are estimated to have diabetes [13]. About 79% lives in low- and middle-income countries. If these trends continue, by 2045, some 629 million people will have diabetes [13]. The estimated population of Malaysia in 2018 is 32.4 million [14]. There were almost 3.49 million cases of diabetes in Malaysia in 2017 [15]. The percentage of population aged 15–64 years old (working age) increases from 69.6% in 2017 to 69.7% in 2018. The percentage of 65 years and over (old age) population increases from 6.3 to 6.5% for the same period [14]. The number of deaths was divided into two groups of ages which are age between 30 and 69 years old as well as ages more than 70 years old. For example, the number of diabetes deaths for female ages more than 70 years old

Cognitive function can be defined as mental process (cerebral activities) that lead to the gaining of knowledge which allows people to carry out their daily life activities [16]. Cognitive functions are mainly related to remembering, solving problems, making decision and understanding the language, problems or even issues like personal issues and health issues, focus, attention and others [2]. It also can be defined as memory which is tested by the stimuli either spoken or presented using another talking format or talking memory [17]. Moreover, it can be related to the large spectrum of cognitive capability among the middle- and old-aged group of people, which are having dementia as well as maintaining normal physiological function [18].

Cognitive impairment is a type of disorder which has not been studied and explored as the complications of DM. At the same time, the association of DM with cognition is well acknowledged. The meta-analysis shows small to moderate performance decline in persons with diabetes relative to nondiabetic controls in each domain examined. The motor function is largely affected, while attention/concentration is affected minimally [19]. Another study shows that people with type 2 DM will have higher rate of cognitive impairment than people that do not have DM [20]. Besides that, the effect of diabetes on the normal mental functions is often disregarded. This may be due to lack of signs and standard assessment technique to measure the cognitive function of the diabetes patient [21]. Hyperglycaemia which is common in people with diabetes has been associated with an increase in the possibility of developing Alzheimer's disease and vascular dementia in both the general public and people with cognitive impairment [22]. It has been estimated that an individual with DM is 1.5 times more likely to experience cognitive dysfunction and

Elderly people who are more than 65-year-old will have more than 20% chances

to be diagnosed with both DM and impaired cognitive function [24]. Type 2 DM has been associated with few cognitive impairments such as decreases in

**62**

psychomotor speed, processing speed, visual retention, attention, concentration and many more. It is understood that more significantly hyperglycaemia, vascular disease, hypoglycaemia and insulin resistance affect cognitive decline, but the exact pathophysiological mechanisms not of cognitive decline in diabetes are unclear [3]. The causes of cognitive decline in diabetes may be the direct effect of the chronic hyperglycaemia on the brain regions, blood lipid, blood pressure, hypoglycaemia and others [25].
