HIV incidence increasing among gay men in Amsterdam

The rate of new HIV infections among gay men in Amsterdam has increased steadily since the introduction of effective antiretroviral therapy, investigators report in the online edition of AIDS.

Receptive unprotected anal sex, a larger number of partners and recent infection with gonorrhoea were all associated with an increased risk of infection with HIV. Most of the infections were acquired from casual partners, but the researchers also found evidence of transmissions within relationships.

Trends in new HIV infections have been monitored over 25 years in the Amsterdam cohort, and the investigators comment, “to our knowledge, this is the first study in recent years to document the HIV-1 incidence rate and risk factors for HIV transmission among MSM [men who have sex with men] in an observational cohort.”

They believe that their results provide “evidence for ongoing substantial HIV transmission among MSM” and that increased levels of testing alone cannot explain why HIV prevalence has risen substantially among gay men in recent years.

In industrialised countries like the Netherlands gay men remain a focus of the HIV epidemic. Several countries have reported increased numbers of new HIV diagnoses among gay men, and studies have also shown that more gay men are reporting unprotected anal sex – the sexual activity most associated with HIV transmission.

Investigators from the Amsterdam Cohort Study wished to gain a clear understanding of HIV incidence and risk behaviour among gay men. They therefore analysed 25 years of data gathered between 1984 and 2009.

A total of 1642 gay men who were HIV-negative at the time of recruitment to the cohort were included in their analysis. Every three-to-six months the men were tested for HIV and completed questionnaires about their recent sexual behaviour and history of sexually transmitted infections.

Median age at the time of recruitment was 29 years, 81% of the men were Dutch and 55% had a college degree. Individuals were followed for a median of 6.2 years.

There were 217 incident HIV infections, and the median age at seroconversion was 34 years.

HIV incidence was 8.6 per 100 person years in 1985, but then fell sharply and was 1.3 per 100 person years in 1992. Incidence then remained relatively stable and was 1.4 per 100 person years in 1996, the year effective HIV therapy was introduced. Thereafter a modest but steady increase in incidence was seen, reaching 2.0 per 100 person years in 2009.

However, the investigators note that the increased incidence in recent years was not significant.

Accompanying these incidence trends were changes in HIV risk behaviour.

Over three-quarters of men reported recent unprotected anal sex in 1984, but this had fallen to 33% in 1988, but this had increased to 38% by the end of 1995, and by the end 2009 the proportion of men reporting unprotected anal sex in the previous six months was 55%. This increase was significant (p < 0.01).

Risk factors for infection with HIV were not having a degree (risk ratio [RR] = 2.00; 95% confidence interval [CI], 1.24-3.21), having five or more recent sex partner (RR = 2.54; 95% CI, 1.58-4.08), receptive unprotected anal sex (RR = 4.06; 95% CI, 2.37-6.96), and a recent history of gonorrhoea (RR = 5.84; 95% CI, 2.49-13.71).

In three-quarters of cases, the source of the incident infection was a casual partner.

But steady partners were an increasingly important source of new infections, especially for older men.

“It could be that…older men are more likely to have a partner who is also older and therefore has a higher probability of being HIV-infected,” suggest the investigators. They also propose that older men and those in longer relationships “often break negotiated safety rules…due to changes in sexual preferences, relationship context, and for other reasons.”

 “Followed by increases in sexual risk behaviour from 1996 onwards, HIV continues to spread among MSM,” conclude the investigators, “receptive unprotected anal intercourse with casual partners remains the strongest risk factor for acquiring HIV infection.”

The investigators recommend that men with casual partners should be a prevention priority. However, they also stress “our findings also suggest the need to pay specific attention to prevention measures regarding sexual behaviour with steady partners.”