As we have
seen, the study included three comparison groups:

  • HIV-positive people
  • HIV-negative people
    with a similar lifestyle to the HIV-positive people
  • Blood donors.

The 134
HIV-positive and 79 HIV-negative people with similar sociodemographic and lifestyle
factors were enrolled in the Co-morbidity in Relation to AIDS cohort (COBRA, a
European Union funded cohort that evaluates age-associated non-communicable
co-morbidities in persons with HIV). They were recruited from HIV outpatient
clinics in Amsterdam and sexual health clinics in London, between 2011 and 2014.

All of these
participants were 45 years old or older (over 50
in London). HIV-positive
participants had to have an undetectable HIV viral load ( 50 copies/ml) for
at least 12 months and be taking antiretrovirals.

A number of people were excluded from the study: individuals
of any HIV status who suffered from major depression; had specific neurological
diseases, previous severe head injury, a history of cerebral infections, excess
alcohol intake, severe psychiatric disease, contraindication to MRI scan or
lumbar puncture examination; used intravenous injectable
drugs (in the past six months) or took recreational drugs daily (except
cannabis).

The 35 blood
donors from the Dutch national blood bank were age-matched with all the COBRA
participants. They had screened negative for HIV, HBV, HCV, syphilis and human T-lymphotropic virus (HTLV) 1 and 2, as required for blood donations in the Netherlands, and had responded to
a questionnaire about their general health, sexual health, medication use,
sexual risk behaviour and travel, without raising any concerns about health risk factors.

To summarise the complex study, the investigators
wanted to compare ageing, by testing an algorithm of biological markers in two groups
who were fairly similar except for HIV, and in blood donors, one of the
healthiest groups in the Dutch population. (The blood donors have few
inflammatory factors such as viral infections.)