**1. Introduction**

Alzheimer's disease is the most common form of dementia, and it accounts for about 60–70% of the 50 million people suffering from dementia worldwide [1]. This means that between 30 and 35 million of people suffer from Alzheimer's disease across the world. However, the numbers of those with this disease may be underestimated as only about 40–50% of the cases of dementia are identified in developed countries [2].

Dementia and, in particular, Alzheimer's disease are a major reason for the disability and dependency across older people. The individual impact burden due to this disease is broad. It includes physical, psychological, social and economic aftermaths. But also the burden is shared with carers, families and society in general [1]. About 50% of carers say that their own health was affected by the responsibility of caring their Alzheimer's patients despite their positive sentiments about their role [3]. The economic repercussions of Alzheimer's disease are diverse, and they include the direct medical costs, the social care costs and the costs of informal care. The magnitude of these economic repercussions cannot be ignored neither by society nor by politicians.

The aim of this chapter is of twofold. Firstly, we review the phenomenon of ageing and describe the increasing prevalence of Alzheimer's disease; additionally, we highlight the relevance of informal care and the burden supported by informal caregivers. Secondly, this chapter aims to describe the social and financial burden of informal caregivers of Alzheimer's patients in Portugal and to estimate a monetary value for the care they provide and have to bear.

The chapter proceeds with a section describing the ageing phenomenon and Alzheimer's disease, as well as the increasing prevalence of this disease. Next, it reviews the type of care available to deal with Alzheimer's patients, and a particular emphasis is placed on informal care. In the following section, the socio-economic burden of informal caregivers is outlined. The chapter continues with a section presenting the estimation of the financial burden of carers of Alzheimer's patients in Portugal followed by a conclusion section.
