Dementia: types and manifestations

It is estimated that there are currently 47,5 million people in the world living with dementia and that this number tends to double every 20 years, reaching 75,6 million in 2030 (WHO, 2015). This reality as a profound impact on life quality and economy of families and nations, representing, in the past years, one of the greatest public health challenges/priorities to face (WHO, 2012).

Adding to the estimated number of persons with dementia is the even greater number of persons with Mild Cognitive Impairment (MCI) – 9,9% to 21,5% of new cases per year, in persons above 65 years old, with amnestic MCI (Mariani et al. 2007), with a progression to dementia rate between 10% to 15% per year (Petersen et al., 1999). Given this, there is also a corresponding number of primary caregivers and overburdened families and at risk of physical and psychological diseases.

The estimated number of Portuguese aged above 60 with dementia was 160 287 (5,91%).

Alzheimer Disease represents 50-70% of Dementia cases (between 80 144 and 112 201 patients).

Main types of Dementia

Alzheimer Disease – This is the most common type of dementia (about 60% of all cases) and, despite not being a consequence of aging, this a condition that increases its incidence with aging. It starts by affecting memory and, later, other cognitive competences (brain functions) such as language, attention, orientation and reasoning ability. Therefore, there are behavioural, personality and functional ability changes which progressively compromise daily life activities. Progression levels are quite different from person to person.

Vascular Dementia – The second most common type results from a deficiency in blood supply to the brain, caused by Transient Ischemic Attack (TIA) or Small Vessel Disease (slow progressive ischemia) which may lead to: (i) changes in the cerebral cortex, affecting learning, memory and language (multi-infarct dementia) or (ii) changes in white matter (internal part of the brain), causing slowness and sleepiness, emotional lability and urinary incontinence (Binswanger's disease or Subcortical Arteriosclerotic Encephalopathy). This type of dementia usually allows preservation of personality and condition consciousness (awareness of the disease). Some of the highest risk factors are hypertension, smoking, diabetes and hypercholesterolemia.

Lewy Body Dementia – This type of dementia has similar features to those of Alzheimer and Parkinson diseases and is caused by degeneration and death of brain nerve cells (due to abnormal structures that develop inside this cells – Lewy’s bodies). The symptoms of this disease are: attention and concentration difficulties, visual hallucinations and difficulty in evaluating distances (increased risk of falling), confusional states and disorientation (temporary and intermittent), tremors and muscle stiffness (Parkinsonism). Given the high sensibility to antiparkinson drugs and depot neuroleptics (antipsychotics), it requires greater specialist supervision, to avoid severe secondary effects.

Frontotemporal dementia – This is the 3rd most common cause of dementia in patients aged 65 or above and results from a progressive loss of brain nerve cells, located on frontal and temporal lobes. These losses are evidenced in three different ways (subtypes), which may combine/group together during the degenerative process. The common base symptoms are behaviour and language changes, essentially the following: disinhibition, apathy, loss of self-criticism, repetitive behaviours and an impoverished and stereotyped speech, associated to paraphasia (replacement of words by others of similar context). On a cognitive level, these patients present deterioration of executive abilities (planning, systematization) and attention. Memory problems appear in a later stage, which makes diagnosis harder and often detection of disease is only possible after a detailed neuropsychological evaluation.

Frontotemporal dementia – this is the most common subtype (Frontal variant) and manifests itself through changes in social behaviour, with an insidious mark, making the person disinhibited (and lacking self-criticism) or apathic (and without emotional expression). There is also an evident sloppiness in selfcare and lack of interest in activities once practiced, as well as difficulties in planning and space organization.

Non-fluent Progressive Aphasia – This subtype is evidenced through language changes (also insidious), manifested through a spontaneous non-fluent speech, difficulties in articulating words (hesitation, suppression, replacement and absence) and loss of grammar logic.

Semantic Dementia – In this subtype, the person has a fluent but empty speech (unlike in the previous one). Besides replacing words for others of similar context (paraphasia), the person may also loose de ability to understand, give meaning and organize words in sentences. In some cases, prosopagnosia (inability to recognize the identity of familiar faces) or associative visual agnosia (inability to recognize familiar objects) may also happen.