Individuals 50 Years of Age and Older Are at Risk for HIV Infection and Other Sexually Transmitted Diseases

People aged 50 and older are more likely to have unprotected sex than younger individuals with HIV infection, which increases their risk for HIV and other sexually transmitted infections (STDs), according to results of a recent study supported by the World Health Organization (WHO) published in the current Bulletin of the World Health Organization.

"As people in developing and industrialized countries increasingly live longer, healthier lives, why do the scant data that exist suggest a surprisingly high prevalence and incidence of HIV among individuals 50 years of age and over ("older individuals")?" asked the authors of the WHO study.

Older individuals are rarely included in Demographic Health Surveys (DHS), they noted. In the last 5 years, only 13 of 30 surveys included older males and none included older females. The National Health and Nutrition Examination Survey in the U.S. (NHANES) does not collect data from people older than 49.

Incidence and Prevalence of HIV Infection in Older Individuals
HIV incidence could be determined via case reporting, serologic incidence assays or modeling, the authors noted. Incidence refers only to new infections. Developing countries have limited case-reporting systems, but industrialized countries do better.

In the U.S., case reporting from 2003 through 2006 shows that the proportion of older HIV positive individuals has climbed from 20% to 25% of all people with HIV, and case numbers have risen in all 5-year age bands from 45 years to 65 years and older.

Based on specialized serology tests, 11% of incident HIV cases in 2006 were in older individuals. In WHO's European Region, 8% of reported cases in 2005 occurred in older people. Similar data from developing countries are unavailable, and modeled incidence data are not publicly available.

To date, the authors wrote, "There is a dearth of prevalence data." Prevalence refers to the total number of existing cases in a population.
The authors calculated HIV prevalence by age, using UNAIDS' estimated numbers of cases of HIV and United Nations population estimates by country.

"One finds a consistent pattern that prevalence in older individuals is one-quarter to one-third that of the 15-49-year age group," they wrote. "We have debated with our colleagues whether these findings are surprising. Most of us think 'yes'."

This is particularly so because prevalence for this age group is deceptively low. "There is little appreciation that the older the individual, the faster the progression from HIV infection to AIDS," wrote the authors. "The effect is considerable, linear, and remains after adjusting for all-cause mortality."

A life expectancy of more than 13 years is expected for HIV positive people aged 5-14 years. However, life expectancy declines to 4 years for those infected at age 65 or older, and "waning immunity with age may be the reason," according to the authors.

They suggest that because HIV incidence is indirectly related to duration of disease, prevalence in people aged 50 and older should be approximately doubled to be compared with those in the 15-24 year age group.

"While long-available antiretroviral therapy (ART) could increase prevalence among older individuals in industrialized countries" -- because HIV positive people survive longer -- "this is not true of the developing world, where ART was introduced later," they wrote.
Is the epidemiology of HIV in older individuals of purely academic interest?

"No," wrote the authors, "because understanding risk factors leads to interventions." Intriguingly, they added, "the Alpha Network in Africa has shown that in many sites, secondary peaks of HIV incidence appear at older ages."

Why Might Older Individuals Acquire HIV?

As to why older individuals acquire HIV, the authors wrote, "We can only conjecture."

In a literature search, they found only a single, limited epidemiological study (looking at an urban U.S. population) that evaluated HIV acquisition in older individuals.

Sexual activity of older individuals in the developing world is barely researched. "Many older individuals everywhere are sexually active, although interest in sex and frequency of vaginal intercourse decline with age," wrote the authors.

Since 1998, erectile dysfunction drugs such as Viagra have extended the sex life of many older individuals, and at the same time "may be extending the HIV epidemic into older age groups," according to the authors.

Several studies have shown that older individuals are less likely than younger people to practice safer sex. "While erectile dysfunction is common and erectile dysfunction drugs are widely distributed in developing countries, no study has been done of their possible impact on the HIV epidemic, although their use in industrialized countries has been associated with risky sexual practices," wrote the authors. "Whether HIV positive men should be prescribed these drugs has been debated."

"If sex is the main cause of HIV infection in older individuals and many older individuals are not having penetrative intercourse, then the risk of acquiring HIV per sexual act in these individuals must be high," the authors continued. "We can only speculate what the reasons may be."

The thinning of vaginal mucosa with age may play a role, they suggested. For both men and women, the prevalence of antibodies against herpes simplex virus 2 increases with age, indicating continual risky sexual behavior and enhanced risk of HIV transmission.

While sexual activity is the most likely mode of HIV transmission, further research is required to establish the relative contribution of different risk factors and modes of transmission, according to the authors.

"One consistent finding is the failure to consider HIV as a cause of illness in older individuals," they continued. "These individuals have a shorter time from diagnosis to onset of AIDS, reflecting both age-related faster progression to AIDS and doctors' failure to consider HIV as a diagnosis. Screening is less common for older adults, who are assumed not to be at risk."

In conclusion, the authors wrote, "HIV prevalence and incidence in the over-50-year-olds seem surprisingly high and the risk factors are totally unexplored. Understanding the epidemiology of HIV infection in older individuals can lead to interventions to make these years safer and more enjoyable."

Department of HIV/AIDS, World Health Organization, Geneva, Switzerland; St Olaf College, Northfield, MN.



GP Schmid, BG Williams, JM Garcia-Calleja, and others. The unexplored story of HIV and ageing. Bulletin of the World Health Organization 87(3): 161-244. March 2009. (Full text).