**2. Ageing and the Alzheimer's disease**

The current major demographic phenomenon in Europe is ageing. The share of older people in the population is increasing, and the age distribution picture is changing to an oval shape, and it is tending to look like a block. The ageing trend may be explained by (i) the increased longevity of people, (ii) the declined fertility and (iii) the ageing of "baby boom" generations.

In Europe, as the cohort of baby boomers gets older, the wider stripes of the pyramid move up in direction of the top of the pyramid. Younger generations and their low fertility are reflected by their narrow stripes at the base of the age pyramid. As the time goes by, the top highest age group of the pyramid enlarges as an increasing large share of very old people who are living longer lives (**Figure 1**) [4].

So life expectancy has been increasing and people are living longer. These longer lives may be lived in a healthy status, but most likely the additional years of life are lived in unhealthy conditions, in particular, the last years of life. Among the health conditions, the most prevalent in older ages is dementia, which includes Alzheimer's disease. This health condition is not a consequence of the ageing natural process, but it has a high prevalence among the older group of people [5]. It generates high economic and social costs, and for this reason it may be considered as one of the great challenges of society nowadays [5].

**Figure 1.** *Population age pyramid in Europe.*

*The Burden of Informal Caregivers of Alzheimer's Patients: An Estimation to Portugal DOI: http://dx.doi.org/10.5772/intechopen.90673*

#### **Figure 2.**

*Standardised death rate due to Alzheimer's disease. Source: Based on Eurostat [hlth\_cd\_asdr2] [8].*

Dementia (and Alzheimer's disease) is a syndrome, chronic or progressive, characterised by an abnormal and fast decline in the ability of people to reason and think (the decline of the cognitive function). Although consciousness is not affected, the remaining capacities are strongly diminished such as memory, thinking, orientation, comprehension, calculation, learning, language and judgement. Additionally, there is a decline in the emotional control and social behaviour [1].

Life expectancy for an Alzheimer's patient, after his diagnosis, is about 10 years. There are three stages of progressive gravity of the disease: early (2–4 years), mild (2–10 years) and late (1–3 years or more) stages. In the early stage, illness goes unnoticed, and its signs include forgetfulness, losing oneself in familiar surroundings and losing track of time. As the illness progresses, at the mild stage, the signs become clear, and patients begin to forget recent events and people's names, forget where they are, have difficulty communicating with others, need help with personal care and start to show behavioural changes as wandering and repeat questioning. When the last stage is reached, Alzheimer's patients are inactive and dependent. Their memories are seriously damaged and physical signs are obvious.

The clinical dementia rating (CDR) is the clinical instrument that measures the severity of dementia, including Alzheimer's disease. This instrument evaluates six domains of cognitive and functional performance of patients, including memory, orientation, judgement and community affairs. This instrument scores the patients impairment in five levels so that medical intervention is more adequate and effective.

CDR is not a clinical diagnosis; it rather is a measurement scale that helps the diagnosis of Alzheimer's disease. In fact, there is no single test that provides a consistent diagnosis of Alzheimer's disease. The diagnosis is a process of careful evaluation done by a multidisciplinary team which may include neurologists, geriatricians, nurses, psychologists and psychiatrists [6].

In Western Europe, in 2016, it has been estimated that 4,499,078 disabilityadjusted life years (DALY) were attributed to Alzheimer's dementia disease [7]. Mortality associated to Alzheimer's disease has been increasing in Europe (**Figure 2**). Women die more than men, but the rate of increase has been identical for both genders. This trend is expected under the current conditions of longer lives and advance medical knowledge.

Currently, there are no medicines that prevent Alzheimer's disease or cure it, and so the numbers of patients and deaths will continue to grow, as well as the burden on the people suffering the disease, on the caregivers and on the health system as a whole.
