RESEARCH
HIV infection in older adults in sub-Saharan Africa: extrapolating prevalence from existing data
Infection à VIH chez les adultes âgés en Afrique subsaharienne: extrapolation de la prévalence à partir de données existantes
Infección por el VIH entre los adultos de mayor edad en el África subsahariana: extrapolación de la prevalencia a partir de los datos existentes
Joel Negin*; Robert G Cumming
University of Sydney, School of Public Health, Edward Ford Building, Sydney, NSW, 2006, Australia
ABSTRACT
OBJECTIVE: To quantify the number of cases and prevalence of human immunodeficiency virus (HIV) infection among older adults in sub-Saharan Africa.
METHODS: We reviewed data from Demographic and Health Surveys (DHS). Although in these surveys all female respondents are < 50 years of age, 18 of the surveys contained data on HIV infection among men aged > 50 years. To estimate the percentage of older adults (i.e. people > 50 years of age) who were positive for HIV (HIV+), we extrapolated from data from the Joint United Nations Programme on HIV/AIDS on the estimated number of people living with HIV and on HIV infection prevalence among adults aged 15-49 years.
FINDINGS: In 2007, approximately 3 million people aged > 50 years were living with HIV in sub-Saharan Africa. The prevalence of HIV infection in this group was 4.0%, compared with 5.0% among those aged 15-49 years. Of the approximately 21 million people in sub-Saharan Africa aged > 15 years that were HIV+, 14.3% were > 50 years old.
CONCLUSION: To better reflect the longer survival of people living with HIV and the ageing of the HIV+ population, indicators of the prevalence of HIV infection should be expanded to include people > 49 years of age. Little is known about comorbidity and sexual behaviour among HIV+ older adults or about the biological and cultural factors that increase the risk of transmission. HIV services need to be better targeted to respond to the growing needs of older adults living with HIV.
RESUMÉ
OBJECTIF: Quantifier le nombre de cas et la prévalence de l'infection par le virus de l'immunodéficience humaine (VIH) chez les adultes âgés en Afrique subsaharienne.
MÉTHODES: Nous avons étudié les données des enquêtes démographiques et sanitaires. Même si, dans ces enquêtes, toutes les femmes interrogées sont âgées de moins de 50 ans, 18 des enquêtes contenaient des données sur l'infection à VIH chez les hommes âgés de 50 ans et plus. Pour évaluer le pourcentage d'adultes âgés (c.-à-d. de personnes âgées de 50 ans et plus) qui étaient séropositives (VIH+), nous avons extrapolé à partir des données du Programme commun des Nations Unies sur le VIH et le Sida (ONUSIDA) sur le nombre estimé de personnes vivant avec le VIH et sur la prévalence de l'infection à VIH chez les adultes âgés de 15 à 49 ans.
RÉSULTATS: En 2007, approximativement 3 millions de personnes âgées de 50 ans et plus vivaient avec le VIH en Afrique subsaharienne. La prévalence de l'infection par le VIH dans ce groupe était de 4%. Elle était en comparaison de 5% chez les 15-49 ans. Sur les quelques 21 millions d'habitants de l'Afrique subsaharienne âgés de 15 ans et plus qui étaient porteurs du virus HIV, 14,3% d'entre eux étaient âgés de 50 ans et plus.
CONCLUSION: Pour mieux refléter la survie plus longue des personnes vivant avec le VIH et le vieillissement de la population séropositive, les indicateurs de prévalence de l'infection à VIH doivent être étendus afin d'inclure les personnes âgées de plus de 49 ans. On sait peu de choses sur la comorbidité et le comportement sexuel des adultes âgés séropositifs ou sur les facteurs biologiques et culturels qui augmentent le risque de transmission. Les services relatifs au VIH doivent être mieux ciblés pour répondre aux besoins croissants des adultes âgés qui vivent avec le virus.
RESUMEN
OBJETIVO: Cuantificar el número de casos y la prevalencia de la infección por el virus de la inmunodeficiencia humana (VIH) entre los adultos de mayor edad en el África subsahariana.
MÉTODOS: Se han analizado los datos procedentes de las Encuestas demográficas y de salud (EDS). Aunque en estos estudios todas las mujeres entrevistadas son menores de 50 años, 18 de estas encuestas contenían datos sobre la infección por VIH en hombres con una edad igual o superior a los 50 años. Para calcular el porcentaje de adultos de mayor edad (es decir, personas de 50 o más años de edad) con positividad al VIH (VIH+), se extrapolaron los datos procedentes del Programa Conjunto de las Naciones Unidas sobre el VIH/SIDA sobre la cantidad estimada de personas con el VIH y sobre la prevalencia de la infección por este virus entre los adultos con edades comprendidas entre 15 y 49 años.
RESULTADOS: En 2007, en el África subsahariana había unos 3 millones de personas de 50 años o mayores con el VIH. La prevalencia de la infección por el VIH en este grupo fue del 4,0%, en comparación con el 5,0% correspondiente al grupo con edades comprendidas entre 15 y 49 años. De la cantidad aproximada de 21 millones de personas > 15 años con VIH en el África subsahariana, el 14,3% tenía 50 años de edad o más.
CONCLUSIÓN: Para poder reflejar mejor la mayor supervivencia de las personas con VIH y el envejecimiento de la población VIH+, se deben ampliar los indicadores de la prevalencia de la infección por el VIH, de manera que incluyan a las personas mayores de 49 años. Se sabe poco sobre la morbilidad asociada y el comportamiento sexual de los adultos VIH+ de mayor edad o acerca de los factores biológicos y culturales que aumentan el riesgo de transmisión. Los servicios relacionados con el VIH deben orientarse mejor para responder a las necesidades crecientes de los adultos de edad más avanzada que se ven afectados por esta enfermedad.
Introduction
Despite the global attention being paid to the epidemic of infection with the human immunodeficiency virus (HIV), HIV infection rates among older adults in sub-Saharan Africa have been a neglected area of study. The Joint United Nations Programme on HIV/AIDS (UNAIDS) and other prominent sources of data report prevalence rates only for those aged 15-49 years, and the indicators used by the United Nations General Assembly Special Session focus predominantly on the same age group. The burden of disease among those aged > 50 years is almost always ignored and this represents a significant blind spot in the global response to the epidemic of HIV infection and acquired immunodeficiency syndrome (AIDS).
As a result of the situation described above, there is a paucity of data on HIV infection in people aged > 50 years. In 2006, UNAIDS shifted to reporting the number of HIV-positive (HIV+) people aged > 15 years, but it provides limited data specifically on those aged > 49. The 2006 report on the epidemic revealed some of the only existing data for this age group and stated that globally "around 2.8 million adults aged 50 years and older were living with HIV in 2005".1 Other estimates have been based on limited data.2 While individuals > 49 years of age account for approximately 10% of the cumulative HIV infection case-load in the United States of America,3 the corresponding proportion for Africa is not known.
The few existing studies on HIV infection among older adults have focused mainly on developed countries.4-9 Studies in developing countries emphasize the social and economic impact of HIV infection - mainly its effect on older grandparents in their role as caretakers of children orphaned as a result of parental HIV infection - and have ignored the prevalence of HIV infection in older people and its impact on their lives.10,11
As more people in sub-Saharan Africa have begun taking antiretroviral treatment, mortality rates have dropped12,13 and HIV+ individuals are surviving longer. At the same time, older people remain at risk for infection. In the light of the ageing of the general population, there is a need to better understand the prevalence and characteristics of HIV infection among older adults in sub-Saharan Africa. To begin to address this information gap, we have used existing data and information to estimate the prevalence of HIV infection among people > 49 years of age in sub-Saharan Africa.
Methods
The data in this analysis came from a variety of sources. The main source was data on the prevalence of HIV infection released by UNAIDS in conjunction with its 2008 report on the global AIDS epidemic.14 The UNAIDS web site provides data, by country and by year, on the estimated number of people living with HIV as well as on the prevalence of HIV infection among adults aged 15-49 years.14 It does not, however, provide the number of HIV+ people aged > 50 years or the prevalence of HIV infection in this age group. To derive those data, we needed to know the total population of each country in sub-Saharan Africa and its age distribution. We obtained the total population of each country from the 2007 world population data sheet15 and extracted the percentage of the total population aged 15-49 years and > 50 years, by country, from World population prospects: the 2008 revision, using data from 2005, the most recent year for which data were available.16 Using population data from 2007 and the percentage of the total population aged 15-49 years, we calculated the number of people aged 15-49 years in each country. The use of UNAIDS data on the prevalence of HIV infection in this age group allowed us to calculate the number of people that had HIV infection. By subtracting this number from the total number of HIV+ people who were aged > 15 years, as calculated by UNAIDS, we estimated the number of HIV+ people aged > 50 years. We then divided this number by the total number of people aged > 50 in a country (as derived from World population prospects: the 2008 revision) to estimate the prevalence of HIV infection among people aged > 50 years.
For this analysis we used sub-Saharan African countries as classified by UNAIDS. Data were not available for Cape Verde, the Comoros or Sao Tome and Principe. For the Democratic Republic of the Congo UNAIDS only provides high and low estimates of the number of people living with HIV. We used the midpoint between the two. UNAIDS data for Kenya for 2007 were awaiting finalization of the Kenya AIDS Indicator Survey, so we used those results, released in 2009, for analysis. 17
Population-based surveys, predominantly the Demographic and Health Surveys (DHS) web site, 18 were a second source of data for this study. We accessed the DHS reports and AIDS Indicator Survey reports on the site. To focus on the most recent data, we reviewed all surveys conducted after 2000 that contained information on HIV testing in countries in sub-Saharan Africa, and we extracted relevant data. Of the 43 DHS reports conducted after 2000 in countries in sub-Saharan Africa, 39 (91%) included interviewees aged > 50, but only if they were men, and the upper age limit for these interviewees ranged from 54 to 64 years. Because the surveys are designed primarily to collect data on maternal and child health, the age ceiling for women interviewees is 49 years.
Of the 39 reports that included interviewees aged > 50, 18 provided data on the prevalence of HIV infection based on population-based HIV testing of interviewees in this age group. The others contained information only on HIV-related awareness and behaviour. Of the four AIDS Indicator Surveys for which data were available, only the Ugandan survey included interviewees aged > 49 years: in that country, both men and women aged < 60 years were interviewed.
In addition, we searched the Internet and the grey literature to identify other sources of data on population-based HIV testing in sub-Saharan Africa. South African data sources and the Kenyan AIDS Indicator Survey were identified through this process.
Results
Based on the analysis of data obtained from UNAIDS and World population prospects: the 2008 revision, we estimated that in 2007 approximately 3 million people aged > 50 years were living with HIV in sub-Saharan Africa. This represents 14.3% of the approximately 21 million people aged > 15 years who are infected with HIV (Table 1). The five countries with the highest number of older adults living with HIV in sub-Saharan Africa were Mozambique, Nigeria, South Africa, Zambia and Zimbabwe; together these countries accounted for 54% of the total number of older adults living with HIV. The estimated prevalence of HIV infection among the 74 million people aged > 50 years in sub-Saharan Africa is 4.0%, compared with 5.0% among those aged 15-49 years.
Table 2 presents information on the prevalence of HIV infection among those aged > 50 years in several countries in sub-Saharan Africa from DHS, AIDS Indicator Surveys and other population-based surveys. The highest prevalence of HIV infection among those aged > 50 years was found in Zimbabwe during 2005-2006: 20% of all men aged 50-54 years were living with HIV.22
The 39 DHS reports that include male interviewees aged > 50 also contain data on HIV-related awareness, behaviour and attitudes. The questions asked during the course of the decade included in our study differ and this makes direct comparisons difficult, but for each country the responses of those aged > 50 years can be compared with those of people < 50. In general, older men are less aware of and knowledgeable about HIV-prevention measures than men aged 15-49. Interviewees in eight countries (Benin, Cape Verde, Ghana, Lesotho, Mali, Nigeria, Uganda and Zambia) were asked the same question about whether using a condom and having only one sexual partner are effective prevention measures, and in seven of the countries (all but Ghana) men aged > 50 years knew less than men < 50. For example, in Nigeria 68.6% (2612/3808) of men aged 15-49 knew that using condoms and having only one partner are effective prevention measures, as opposed to only 58.3% (978/1678) of men aged 50-59.23
In four of the seven countries where interviewees were asked about the number of sexual partners they had had during the past 12 months, namely Benin, the Democratic Republic of the Congo, Ghana and Nigeria, men aged > 50 years were more likely to have had two or more sexual partners than those aged 15-49. In each of these four countries, the percentage of men aged > 50 years who had had two or more sexual partners during the previous 12 months and who had used condoms the last time they had engaged in sexual intercourse was much lower than among men aged 15-49. For example, in Ghana only 7.9% (5/64) of the men aged 50-59 years who had engaged in sex with at least two partners over the previous 12 months had used a condom during their last sexual intercourse, compared with 26.2% (120/459) of men aged 15-49.
Discussion
An analysis of UNAIDS and World population prospects data suggests that approximately 3 million adults aged > 50 years are living with HIV in sub-Saharan Africa. People in this age group account for 14.3% of all HIV+ people > 15 years of age. This study confirms that HIV infection does not affect younger people exclusively.
Comparisons between the two types of data sources used in this study reveal an occasional match between the prevalence of HIV infection estimated from UNAIDS data and the prevalence obtained from population-based HIV testing. For example, in Benin calculations made from UNAIDS data suggest that in 2007 the prevalence of HIV infection among those aged > 50 years was 1.0%; similarly, DHS data for 2006 suggest a prevalence of 1.0% among men aged 50-64. 24 However, in other countries there are significant discrepancies. For Lesotho, data derived from UNAIDS statistics suggest a prevalence of 27.8% in 2007 among those aged > 50 years, whereas according to data from the 2004 DHS, prevalence among men aged 50-59 is around 16%. 25 These surveys do not measure the same indicator: most DHS data cover men in a limited age range, as previously indicated, while UNAIDS data are for all adults aged > 50 years.
The main results presented in this paper depend on the quality of the data obtained from UNAIDS. These data are derived from mathematical and demographic projection models based primarily on prevalence data from population-based surveys, time-trend prevalence data from antenatal clinics, estimates of the need for antiretroviral treatment and its coverage, mortality rates and total population;26-28 they are not designed specifically to quantify the prevalence of HIV infection among older adults. Consequently, prevalence and case-load calculations from UNAIDS reports represent the best available, but they do not allow derivation of exact population numbers. Population-based surveys of HIV infection prevalence among older adults would provide more reliable and robust data.
A few studies have documented HIV infection among older adults: a study in rural Cameroon showed a prevalence of 2.6% among men and women aged 55-70 years,29 and a study among people admitted to hospital in Dar es Salaam, United Republic of Tanzania, reported a prevalence of 15% among those aged > 55. 30 A study in the Congo described 175 cases of HIV infection among people aged > 55 years from 1990 to 1996.31 An 81-year-old male who was HIV+ was identified in an Ethiopian study.32 In general, however, data on HIV infection in older adults in Africa are limited.
Two facets to the issue of HIV positivity among older adults generate particular challenges. One is the occurrence of new cases of HIV infection among older adults and the other is the ageing of the population infected with HIV.33
Previous studies have shown that those who become infected with HIV later in life progress more rapidly towards AIDS and death than those who are infected at a younger age. Justice and Weissman have noted evidence that being older at the time of seroconversion is strongly associated with faster disease progression and shorter survival.34 A study in the United Kingdom of Great Britain and Northern Ireland revealed that those who became infected between the ages of 15 and 34 years had a 10-year survival rate of 72%, compared with 12% of those who seroconverted after the age of 55.35 In 2001, the Collaborative Group on AIDS Incubation and HIV Survival predicted a life expectancy of only four years for people who become infected at age > 65 years.36 A 2001 study in the United States demonstrated that reconstitution of the immune system after initiating antiretroviral treatment was slower in older patients.37
As more people survive longer with HIV, the overall case-load will age and new challenges will arise in sub-Saharan Africa. Older adults have greater comorbidity, experience more side-effects from antiretroviral treatment and hence may be less likely to adhere to treatment.34 The toxicity of antiretroviral therapy, combined with decreased kidney and liver function in older individuals, may lead to treatment difficulties such as drug interactions.38 Studies are needed to better understand the pharmacokinetics of antiretroviral agents in elderly people.39
Common misconceptions about sexual activity among older people remain. A study in Nigeria dismissed older people as no longer being sexually active,40 confirming what Ory et al. called "ageist assumptions about sexual behaviour".33 These attitudes limit the development of appropriate responses tailored specifically to older adults.
Several factors put older people at a higher risk of becoming infected with HIV. The thinning of the vaginal wall after menopause increases the risk of HIV transmission during sex.41 Practices such as wife inheritance and ritual cleansing, in which a widow is expected to either marry or have sex with relatives of the deceased husband, can increase older women's exposure to the virus.42 Additionally, many older people are poor and may not be able to afford health services.
Older adults' access to HIV-related services and information is limited: the UNAIDS update for 2009 stated that "even though the largest share of new infections in many African countries occurs among older heterosexual couples, relatively few prevention programmes have specifically focused on older adults".43 DHS data suggest that levels of condom use and knowledge about condoms are low among older adults. In the United States, Ory and Mack noted that people aged > 50 years who had known risk factors for HIV infection were one-sixth as likely to report using condoms as people in their twenties with comparable risk factors.3 The lack of targeted prevention services becomes even more important considering that many older people care for younger ones, since a lack of knowledge may prevent older people from effectively teaching the next generation about HIV.
The delivery of services to older adults with HIV infection needs to be improved. In the United States, el-Sadr and Gettler have indicated that health-care providers are less likely to attribute signs and symptoms of disease in older people to HIV infection.44 Data from Brazil suggest that older people are diagnosed later in the course of HIV infection, with more AIDS-defining diseases present at diagnosis.45 This may be true for Africa as well.
South Africa has added men aged > 50 years to its list of populations considered to be at greatest risk for HIV infection, according to a 2008 survey.20 The 6.0% prevalence among these men, together with the limited reach of national communication programmes, low levels of knowledge and poor adoption of preventive behaviours, has highlighted the need to focus prevention on this group.
The need to better understand the various HIV-related challenges faced by older adults will increase as the HIV + population ages. Research should be aimed at understanding the specific vulnerabilities and challenges faced by this group. It should focus on understanding the impact of highly active antiretroviral therapy on older people in Africa and on understanding the sexual behaviour and practices of older people.
Barnett views HIV infection and AIDS as posing a new type of challenge for the global community: a "long-wave event" whose "troubling and large-scale effects emerge gradually over decades".46 For the past few decades, the global HIV community has focused on people aged 15-49 years, often ignoring the long-wave elements of the epidemic. A significant percentage of the population - those aged > 50 years - has been largely excluded from HIV prevention and testing services. The high prevalence of HIV infection and the high rates of death from AIDS-related causes among older people in developing countries call for greater efforts to integrate the needs of older people into responses to the HIV epidemic and to strengthen targeted prevention, care and support programmes. 
Competing interests: None declared.
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(Submitted: 21 January 2010 - Revised version received: 20 July 2010 - Accepted: 4 August 2010 - Published online: 27 August 2010)
* Correspondence to Joel Negin (e-mail: joel.negin@sydney.edu.au).