D EMENTIA

Dementia is a syndrome due to disease of the brain, usually affecting people as they are getting older, and is a major cause of disability and dependency among older people (WHO, 2012).

Dementia has a chronic or progressive nature, in which there is disturbance of multiple higher cortical functions, including memory, thinking, orientation, comprehension, calculation, learning capacity, language, and judgement (WHO, 2016). Decline in memory is a key characteristic of dementia. Memory is divided in different subtypes, where short-term memory refers to the ability to remember limited amounts of information for a very brief (seconds) period of time (Atkinson & Shiffrin, 1968). Long-term memory on the other hand refers to the ability to remember larger amount of information for longer periods of time (Atkinson & Shiffrin, 1968).

The long-term memory function involves both semantic memory of general facts and knowledge and episodic memory. Episodic memory is related to one’s own experiences and also involves spatial and temporal characteristics of these experiences (Carlesimo & Oscar-Berman, 1992).

1.1.1. Risk factors for dementia

Aging, genetics and life style factors are the three main risk factors for dementia, where increased age is the most important (Khanahmadi et al., 2015). The incidence of dementia increases exponentially with increasing age with a doubling for every 6.3 year increase in age. At age 60-64 the incidence is 3.9/1000 person per years, and at age 90+, the incidence is 104.8/1000. The incidence of dementia appears to be higher in countries with high incomes, where the incidence doubles every 5.8 years, than in low or middle income countries where the incidence doubles every 8.6 years (Prince et al., 2015) .

Several genes that affect the risk of developing dementia have been identified and studied (Khanahmadi et al., 2015). Genetic risk factors could be divided into early-onset and late-onset

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according to the time of onset, where most studies so far are related to early-onset (Khanahmadi et al., 2015). Among several potential risk genes, the ApoE e4 allele is the best known genetic risk factor for Alzheimer’s disease (Sachdev, 2014). ApoE is suggested to interact with vascular risk factors of dementia, such as hypertension, diabetes mellitus, smoking, and heart disease (van der Flier & Scheltens, 2005). Other modifiable risk factors for dementia are insulin resistance or the metabolic syndrome, high cholesterol, excessive alcohol use, obesity, physical inactivity, high homocysteine levels, depression, traumatic brain injury (Sachdev, 2014). Factors that might protect development of dementia are education, occupation, complex mental activity and physical exercise (Sachdev, 2014), as these are linked to maintenance of cognition (Williams &

Kemper, 2010).

1.1.2. Diagnosis

The diagnosis is based on medical record, clinical examination, cognitive examinations and laboratory tests. The ICD-10 criteria for research are shown in Table 1 (WHO, 1993). All criteria have to be filled in order to establish the diagnosis.

Table 1. Criteria for dementia according to the International Classification of Diseases (ICD-10) (WHO, 1993).

I A decline in memory, mainly evident in the learning of new information.

A decline in other cognitive abilities (e.g. abstraction, judgement, thinking, planning).

II Preservation of sufficient awareness of the environment to be able to assess criterion I.

III A decline in emotional control or motivation, or a change in social behaviour, with one or more of the following: 1) emotional lability; 2) irritability; 3) apathy; 4) coarsening of social behaviour.

IV Duration of six months or more

Severity of dementia is categorized according to degrees of dementia, which are determined by the cognitive domain (memory or other cognitive functions) with the most severe impairment.

This means that a person with moderate decline in memory, but only mild impairments of other cognitive abilities, has a moderate degree of dementia (WHO, 1993).

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When a person is assessed with mild degree of dementia, the degree of memory loss or decline in other cognitive abilities is sufficient to interfere with everyday activities, but not so severe that it makes the person dependent on others. However, tasks that are more complicated cannot be undertaken. For moderate degree of dementia, the degree of memory loss or decline in other cognitive abilities makes the person incapable of living without support from others, and needs help in all tasks beside the most basic chores. When a person is assessed with severe dementia, the person has no longer the ability to retain new information, and often fail to recognize close relatives. The decline is characterized by an absence, or virtual absence, of intelligible ideation (WHO, 1993).

In Norway, dementia assessments are mostly done in the municipalities, often as a collaboration between the general practitioner and health and care services in the municipality. The general practitioner is responsible to diagnose and prescribe necessary treatment, while health and care services is responsible for assessing functional level and need for institutionalization. In order to enable persons with dementia and their families to benefit from the positive educational, social, psychological and pharmacological interventions that are available and to plan for their future with the illness, diagnosis should be made as early as possible (Knapp et al., 2007). Unfortunately, the large majority of people with dementia either do not receive a specialist diagnosis at any time in their illness, or do so only late in the disorder (Knapp et al., 2007). This means that it can be very difficult to rely on information regarding length of time since onset of dementia.

Nevertheless, in the REDIC report, estimated time from onset of symptoms until diagnosis, in average is 3.0 years (Vossius et al., 2015).

1.1.3. Different dementia disorders

The ICD-10 classification of different dementia disorders is divided in Alzheimer’s disease, Vascular dementia, other types of dementia and unspecified dementia (WHO, 2016). Alzheimer disease is a primary degenerative cerebral disease of unknown etiology with characteristic neuropathological and neurochemical features. The disorder is usually insidious in onset and develops slowly but steadily over a period of several years (WHO, 2016).

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Vascular dementia is the result of infarction of the brain due to vascular disease, including hypertensive cerebrovascular disease. The infarcts are usually small but cumulative in their effect. Onset is usually in later life (WHO, 2016).

Cases of dementia due, or presumed to be due, to causes other than Alzheimer’s disease or cerebrovascular disease, are classified as ‘Other types of dementia’. Onset may be at any time in life, though rarely in old age. Examples: Dementia in Lewy body disease, Creutzfeldt-Jakob disease, Huntington disease and Parkinson disease (WHO, 2016).

The category ‘Unspecified dementia’ should be used when the general criteria for dementia are met, but when it is not possible to identify one of the specific types of disorders. Examples are presenile, primary degenerative dementia and senile dementia (WHO, 2016).

Alzheimer’s disease is the most common cause of dementia, and accounts for 60–80% of cases.

Common outcomes are difficulty remembering recent conversations, names or events, apathy and depression, impaired communication, disorientation, confusion, poor judgment, behaviour changes and, ultimately, difficulty speaking, swallowing and walking (Alzheimer's Association, 2015). Vascular dementia accounts for about 10% of the cases. Common outcomes are impaired judgment or impaired ability to make decisions, plan or organize, as opposed to the memory loss often associated with the initial symptoms of Alzheimer’s (Alzheimer's Association, 2015).