New HIV Rate Similar Above and Below Age 45 in 86,836-Person U.S. Study

In the years 2011-2013, people 45 or older acquired HIV infection at a frequency similar to that of younger people in New York City, San Francisco, and North Carolina. This 86,836-person study by the Centers for Disease Control and Prevention (CDC) also found older people to be just as likely as their younger counterparts to report five or more sex partners.

Median age of HIV-positive people in the United States stands between 45 and 49 years, noted CDC researchers who conducted this study. Yet, most HIV prevention efforts target young people, and little is known about rates of new HIV infections in older individuals.

To compare HIV-diagnosis frequency in older and younger people, the CDC explored data from the September 2011 to October 2013 STOP Study, a prospective, nonrandomized analysis of acute HIV infection in three high-prevalence areas: New York City, San Francisco, and North Carolina. Researchers interviewed all newly diagnosed people and contacted their sex partners for HIV testing. A subset of people had HIV polymerase (pol) gene sequencing to determine whether HIV in newly diagnosed people was related to HIV in other people in the study group.

The CDC team defined older age as 45 years or older and younger age as 12 to 44 years. It defined acute HIV infection as:

  • A negative rapid HIV antibody test result AND;
  • A reactive Ag/Ab combination assay OR;
  • A detectable HIV RNA on pooled HIV RNA test AND;
  • A confirmed individual HIV RNA test.

Less than 1.5% genetic distance between pol sequences from two viruses meant those viruses were related.

Among 86,836 STOP Study participants, 12,036 (13.9%) were 45 or older and 1,326 (1.53%) were diagnosed with HIV. Of the 1,326 people diagnosed, 1,132 (85.4%) were interviewed about sex partners and 547 (41.3%) had pol sequencing. Proportions of the three age groups with larger amounts of new HIV infection were almost identical -- for age 25 to 34 (1.65%), 35 to 44 (1.68%), and 45 to 54 (1.65%). Similar proportions of people 45 or older (1.46%) and younger people (1.53%) (P = .8) received a new HIV diagnosis. Among people with newly detected HIV, proportions diagnosed during acute HIV infection were also similar across age groups: 25 to 34 (13.3%), 35 to 44 (13.2%), and 45 or older (13.1%) (P = .86).

A lower proportion of older than younger people met at least one sex partner online (31.5% versus 46.8%, odds ratio [OR] 0.52, 95% confidence interval [CI] 0.35 to 0.78). And a lower proportion of the older group named two or more sex partners (about 10% versus 25%, OR 0.28, 95% CI 0.15 to 0.53). However, similar proportions of the older and younger groups claimed to have five or more sex partners (46.1% versus 40.2%, P = .20).

A lower proportion of older than younger people had pol sequences linked to another STOP Study participant (19.0% versus 30.7%), but this difference lacked statistical significance (OR 0.62, 95% CI 0.31 to 1.22). Among 555 pol sequence-linked infections, 12 (2.2%) involved two older partners (mean 3.5 years apart in age), 481 (86.7%) involved two younger partners (mean 5.7 years apart), and 62 (11.2%) involved an older partner and a younger partner (mean 19.9 years apart).

The CDC investigators cautioned that their data came from a convenience sample of people living in high HIV-prevalence areas, so the results might not apply to all U.S. groups. Nevertheless, with those limitations in mind, they believe their findings "suggest that HIV prevention interventions tailored to older adults and age-discordant relationships may be important to prevent transmission."