Results of a Malawian study suggest that, contrary to usual practices, individuals aged 50 or older should not be routinely excluded from HIV studies, as many of these individuals remain sexually active and at risk for HIV.¹ Although levels of sexual activity declined with age among study participants, a considerable proportion of 50–64-year-olds—84% of males and 50% of females—reported having had sex in the past year. Moreover, 9% of males and 5% of females aged 50–64 tested positive for HIV; although females in that age-group were less likely than 15–49-year-olds to have the virus (odds ratio, 0.5), males aged 50–64 were more likely than younger men to be HIV-positive (2.0).

Most HIV studies and reproductive health programs in Sub-Saharan Africa have focused on persons aged 15–49, and relatively little is known about sexual activity and HIV risk among older individuals. The new study explored these issues using data from the Malawi Longitudinal Study of Families and Health, which has surveyed residents of three rural districts biennially since 1998. The original sample consisted of 1,541 ever-married women aged 15–49 and 1,065 of their spouses; the sample was expanded in 2004 by the addition of roughly 1,500 youth aged 15–24, and in 2008 by the addition of about 800 parents of study participants. The current analysis combined demographic and behavioral data from the 2010 survey with HIV data from 2008. Using both descriptive analyses and multivariate regression analyses that controlled for background characteristics, the researchers compared HIV prevalence, sexual behavior and HIV risk perceptions among men and women aged 15–49, 50–64 and 65 or older. In addition, they used nonparametric regression to examine outcomes and behaviors by age in greater detail.

Of the 3,719 study participants who completed the 2010 survey, a third (31%) were 50 or older, and 13% were 65 or older. The vast majority of men (87%) and women (77%) were married. About two-thirds of respondents had been tested for HIV in 2008. Among females, the overall prevalence of HIV was 7%, and the prevalence among women aged 50–64 (5%) was not significantly different from that among those aged 15–49 (8%). Among males, the prevalence was 5% overall, and was higher among men aged 50–64 (9%) than among younger men (4%). In fact, males aged 50 or older accounted for 43% of HIV cases among men, even though they represented only 33% of the males tested; women aged 50 or older accounted for 16% of female HIV cases and 30% of the tested female sample. For both sexes, HIV prevalence was about 1% among respondents aged 65 or older.

About 90% of men and women aged 15–49 reported having had sex in the past year. Although the proportion declined with age, levels of sexual activity remained substantial. Among men, 84% of those aged 50–64 and 74% of those 65 or older had had sex in the past year; while the decline with age was steeper among women, 50% of those aged 50–64 and 27% of those 65 or older remained sexually active. The proportion of respondents who had had more than one partner in the past year did not differ by age, and was uniformly higher among men (14–20%) than among women (1–2%). About one in four men and women of reproductive age (23–27%) said they worried "a lot" about HIV infection; although this concern was less common among older men and women, 14–15% of those aged 50–64 and 8–16% of those 65 or older said they worried a lot.

In multivariate analyses, a woman’s odds of having HIV were lower if she was aged 50–64 (odds ratio, 0.5) or 65 or older (0.1) than if she was aged 15–49. However, men aged 50–64 were more likely than younger men to be infected with HIV (2.0). Like their female counterparts, men 65 or older had reduced odds of having HIV (0.1). Among both men and women, respondents in the two oldest age-groups were less likely than those aged 15–49 to have had sex in the past year or to be worried about HIV; however, number of sex partners in the past year did not differ by age.

The nonparametric regression graphs indicated that a woman’s likelihood of being infected with HIV peaked in her 30s and then steadily declined, while a man’s did not peak until about 10 years later and remained stable for another decade. At nearly every age, men were more likely than women to be sexually active and to have had multiple partners in the past year. The proportion of women who worried a lot about becoming infected with HIV was highest during adolescence and early adulthood (30–37%) and declined steadily, nearly disappearing by age 90; among men, the proportion started lower (about 25%), declined much more slowly and leveled off around 18% at about age 60.

The researchers conclude that individuals 50 or older can, and should, be included in HIV research and prevention efforts in Sub-Saharan Africa; they note that if their study, like most, had been restricted to individuals aged 15–49, they would have missed more than two-fifths of the HIV-positive males and one in six of the HIV-positive females in the sample. Moreover, they note that as access to antiretroviral drugs spreads throughout Sub-Saharan Africa, "it is likely that HIV-positive individuals will live to older ages," and that the "sexual behavior of older individuals may be of increasing significance in determining the future of the HIV/AIDS epidemic." —P. Doskoch

REFERENCE

1. Freeman E and Anglewicz P, HIV prevalence and sexual behaviour at older ages in rural Malawi, International Journal of STD & AIDS, 2012, 23(7): 490–496.