In Brazil, from 1980 to June 2016, 842,710 cases of AIDS were reported. In Portugal the incidence is lower but it is equally worrisome compared to EU data. The rate of AIDS in Brazil has stabilized in the last ten years, with an average of 20.7 cases / 100 thousand inhabitants; there is also stabilization of the rate in the Center-West region, with an average of 18.5 cases / 100 thousand inhabitants. The Southeast has a significant downward trend in the last ten years; in 2006, the detection rate was 23.5, increasing to 18.0 cases / 100 thousand inhabitants in 2015, which corresponds to a decrease of 23.4%. However, the North and Northeast regions present a linear tendency of growth of the HIV incidence rate; in 2006 the rate was 14.9 (North) and 11.2 (Northeast) cases / 100 thousand inhabitants, while in 2015 the rate was 24.0 (North) and 15.3 (Northeast) , representing an increase of 61.4% (North) and 37.2% (Northeast). The South region presented a slight tendency of fall of 7.4%, going from 30.1 cases / 100 thousand inhabitants. in 2006 to 27.9 in 2015 (Brasil, 2016).

Among men in the last ten years, there has been an increase in the HIV incidence rate, especially among those aged 15 to 19, 20 to 24 years and 60 years and over. Among women, it is observed that the incidence rate is showing a downward trend in almost all age groups, except those aged 15 to 19, 55 to 59 and 60 years and over, representing 12.9%, 2.7 % and 24.8% increase from 2006 to 2015, respectively (Brasil, 2016).

In Portugal, in 1990, 990 new cases of HIV infection were diagnosed and at the end of the year 54,297 cases were registered, of which 21,177 were in the AIDS stage. Until 2016, the number of new cases of human immunodeficiency virus (HIV) infection continues to decline. In 2016, 841 new cases were diagnosed, 357 fewer than in the previous year and almost half of those diagnosed in 2014, according to the report of the Directorate-General for Health (DGS, 2017), which takes stock of HIV infection, AIDS and Tuberculosis. The 841 new cases represent a rate of 8.1 new cases per 100,000 inhabitants, above the average of the European Union countries with a rate of 6.3 new cases per 100,000 inhabitants. Of the 841 cases, 161 had AIDS. It is estimated that 45,501 people live with AIDS in Portugal, of which 41,073 are diagnosed.

The new diagnoses occurred mostly (99.9%) in individuals aged ≥15 years, 49.3% of whom lived in the Lisbon Metropolitan Area, 72.9% in men, the median age at diagnosis was 39 , 0 years, 72.0% reported being born in Portugal and 15.0% had an AIDS-defining pathology at the time of diagnosis of the infection. According to the initial CD4 count, 49.0% of the new cases corresponded to late diagnoses. The mode of infection was indicated in 94.9% of the cases, with 54.4% referring to heterosexual transmission.
The cases that reported transmission due to sexual relations between men corresponded to 53.8% of the male cases and presented a median age of 31.0 years. Drug-related infections are equivalent to 4.6% of the new diagnoses in 2015. The analysis of the epidemic trends since 2008 has shown a consistent decline in the rate of new diagnoses, however, Portugal continues to have one of the highest rates in EU. Recent trends show a marked decrease in cases of infection associated with drug use, an increase in new cases in young men who have sex with men and a high percentage of late diagnoses, particularly in heterosexuals.

With the increase in the number of cases of HIV infection in the adult and elderly population, issues related to the evolution of AIDS have worried the scientific community around the world due to the complexity involved in aging itself, such as immunity problems, cognitive impairment, dementia and worsening of chronic diseases. The experience of sexuality at this stage of life in infected people with memory decline can be a public health problem.

This is aggravated by the fact that HIV infection in the age group of 50 years or older is diagnosed late because it is only done after extensive investigation and exclusion of other diseases, which may delay the diagnosis and its treatment (Gomes, Silva, 2008). In addition, those diagnosed with AIDS at the age of 50 years or more have high morbidity and mortality.

With the increasing number of cases of HIV infection in the elderly, issues related to the evolution of AIDS in this population have worried the scientific community around the world due to the complexity involved in aging itself, such as immunity decline, cognitive decline and dementia . Memory deficits in adults with HIV may be associated with low adherence to the treatment.

The occurrence of neurocognitive disorders in HIV-positive patients may be due to virus action, treatment or social isolation. The main target of the virus is the lymphoid system; however, the Central Nervous System (CNS) is affected by HIV from the beginning of the infection and throughout its course, being the individual symptomatic or not, being commonly found in cerebrospinal fluid and brain tissue (Christo et al., 2005).

Neurocognitive disorders associated with HIV (HAND) are prominent among the neurological manifestations. People with HAND have impaired learning and motor skills, mood swings and deficits in the cognitive domains that may be related to non-adherence to antiretroviral treatment, which requires regular use (D’Armino-Monforte, 2000).

In addition, the occurrence of cognitive decline in users aged 50 or over, who are still sexually active, may be responsible for a greater spread of HIV infection. The main goals of this study are the promotion of the adherence to antiretroviral treatment, through an intervention program to increase the adherence to treatment in this specific population.