Human Immunodeficiency Virus (HIV) in Older People

Gary Pratt; Kate Gascoyne; Katherine Cunningham; Anne Tunbridge

Disclosures

Age Ageing. 2010;39(3):289-294. 

In This Article

Abstract and Introduction

Abstract

The number of older people living with human immunodeficiency virus (HIV) in the UK is rising. Older people are at risk of acquiring HIV infection for a multitude of reasons. This, combined with effective HIV treatment which has significantly prolonged life expectancy, means that health care professionals working in the UK can expect to see increasing numbers of older people with HIV infection.
In this review article, we summarise the epidemiology of HIV amongst older people, including data from our local cohort in the city of Sheffield, UK. We discuss specific and practical issues in older patients including why older people are at risk, how to make a diagnosis and the importance of doing so early, guidelines for HIV testing and an update on anti-retroviral therapy including drug interactions and side effects.

Introduction

Human immunodeficiency virus (HIV) was isolated as the causative agent for acquired immune deficiency syndrome (AIDS) in the early 1980s in the USA. It has since become a worldwide health problem with over 25 million deaths being attributable to AIDS. The number of people living with HIV in the UK has continued to rise each year since the mid-1980s.[1]

The introduction of highly active anti-retroviral therapy (HAART) in 1996 has revolutionised HIV treatment leading to a steep decline in the number of AIDS cases presenting each year and a significant improvement in patient survival.[2] This, in combination with other factors such as increased HIV risk behaviours in older adults and a lack of targeted prevention campaigns, means that health care professionals working in the UK will encounter greater numbers of older people living with HIV in their day-to-day clinical practice.

Epidemiology

In the UK an estimated 77,400 people were living with HIV at the end of 2007 with nearly a third of these individuals unaware of their diagnosis. During 2008 there were 7,370 new diagnoses of HIV, of which just over half were acquired through heterosexual contact — mostly black Africans who were infected outside of the UK. Approximately 38% of new diagnoses were made in men who have sex with men. Almost a third of new HIV diagnoses were made late (that is, with a CD4 count <200 per mm3) — a group in whom morbidity and mortality is significantly increased.[1]

According to the Center for Disease Control and Prevention, in 2005 in the USA, 15% of new HIV diagnoses and 24% of the entire HIV population across 33 states were made up of people aged 50 and over. This prevalence data represents an 8% increase from 2001.[3] However, true rates of HIV infection in this age group are difficult to determine due to low rates of testing.[4]

In Sheffield we have a cohort of 660 individuals with a diagnosis of HIV, of whom 18 (3%) are aged 60 years or over. Of these 18 patients, 14 are male (78%) and 4 (22%) female, the oldest being 76 years old. Eight of the 18 patients (44%) were diagnosed after the age of 60. Since 1993 we have also seen 10 patients aged over 60 die as a result of HIV infection.

Pathophysiology

HIV infects CD4+ T Lymphocytes, and disease manifestations are largely a consequence of the decline in CD4+ T cells causing immunosuppression. Initially, there is a period of rapid cell turnover with CD4+ cells being infected at a high rate but rapidly cleared by cytotoxic (CD8+) T lymphocytes and then replaced from a precursor pool. Eventually, the patient enters the terminal stages of HIV disease as a result of exhaustion of the stem cell reservoir and/or the rapid replication and mutation of the virus to generate wide antigenic diversity which 'outruns' the CD8+ cell response. This process takes on average 10–15 years.[5]

At a cellular level, HIV surface protein gp120 binds to CD4 and a chemokine co-receptor on the surface of the host cell. The virus then fuses with the cell surface membrane and releases its contents (RNA + viral enzymes) into the cytoplasm. Within the nucleus, viral reverse transcriptase transcribes HIV RNA to create double-stranded DNA. Viral integrase then splices HIV DNA into host chromosomal DNA to create a 'provirus'. When a CD4+ cell harbouring provirus is activated (either against HIV or another pathogen), it replicates and produces new copies of the viral genome and viral proteins. HIV protease then modifies the proteins produced such that they can be packaged together with copies of viral RNA to create new viral particles which bud from the cell and can infect other cells.[5]

Various theories have been proposed which suggest that elderly patients may be at greater risk of HIV disease progression and poorer response to treatment. These include:

  • thymic involution and corresponding low 'T cell reserve' which may impair recovery of CD4+ cell numbers with treatment[6]

  • the association of ageing with increased expression of key T cell chemokine co-receptors which may facilitate viral entry into certain immune cells.[7]

  • the fact that older adults have reduced production of IL-2 and IL-2 receptors which affects T cell function and promotes a shift from naïve to more terminally differentiated T cells, and thus leads to immunosenescence.[8]

Why are Older People at Risk?

There are several reasons why the elderly population is at risk of HIV infection:

  1. The few HIV prevention campaigns that do exist do not target the elderly.

  2. Older people may not consider themselves at risk of HIV infection.

  3. Health care providers may not consider the diagnosis in older patients and therefore may not undertake HIV testing or may attribute symptoms of HIV to 'normal ageing'.

  4. Despite the stereotypes, many older people lead sexually active lives. Studies of sexual activity in people aged over 50 showed that 81.5% were involved in one or more sexual relationships including sex with prostitutes,[9] and a national US survey suggested that only a small minority of people over 70 consistently used condoms.[10] Older women may be especially at risk because age-related vaginal thinning and dryness can cause tears in the vaginal wall.[11]

  5. The increase in foreign travel makes access to countries with thriving sex industries easier.

  6. The introduction and usage of potency drugs has extended the sex lives of many elderly males.

  7. Injection drug usage, despite our misconceptions, is a contributor to HIV transmission in older people. In the USA, injection drug use accounts for more than 16% of AIDS cases in those aged 50 or over.[12]

  8. The stigma of HIV may be perceived to be greater in the elderly population leading them to hide their diagnosis or avoid testing.

Making a Diagnosis

HIV is now a treatable medical condition with the potential for long-term survival. Despite this, there are still a significant number of people living in the UK unaware of their diagnosis. A national audit in 2006 conducted by the British HIV Association (BHIVA) showed that 24% of all deaths amongst HIV positive individuals was attributed to the diagnosis of HIV being made too late for effective treatment.[13] Furthermore, there is evidence that many of these late presenters had been recently seen by a health care professional without the diagnosis of HIV being considered.[14]

In our Sheffield cohort, five of the 18 patients (28%) in the over-60 age group presented late (CD4 count <200/mm3). Seven (39%) had recently been seen by a health care professional without the diagnosis being made. Perhaps even more significantly, of the 10 patients that died as a result of their HIV infection since 1993, seven (70%) presented late.

There is still a widely held but erroneous belief that HIV testing requires lengthy pretest counselling by an expert in this field. The outlook for many people testing positive for HIV is significantly better than for many other conditions for which we test routinely. People currently being diagnosed with HIV are considered to have a standardised mortality ratio of 1.4, similar to that for a diagnosis of type 2 diabetes.[15] Whilst patient consent for testing is required, national guidelines on HIV testing state that 'it should be within the competence of any doctor or healthcare professional to obtain informed consent for testing'.[16]

BHIVA recommends that a fourth generation laboratory assay which tests for both HIV antibody and p24 antigen be used for HIV testing. This has the advantage of minimising the 'window period' between infection and positive testing to 4 weeks.

Point of care testing has been introduced in some centres with the advantage of a result from a finger prick or mouth swab being available within minutes. It is hoped that this may increase the uptake of voluntary testing. However, all positive tests obtained using this method should be confirmed by laboratory serological testing.[16]

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