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How common is neurocognitive impairment in people with HIV? It depends who you compare them with
Gus Cairns, 2011-10-13 17:40:00
How much more common is brain impairment and dementia in people with HIV than in the general population? A study presented at the 13th European AIDS Conference in Belgrade today showed that the answer could vary from 'no more common' to 'four times as common' according to which group you studied, which sample of the HIV-negative population you compared them with, and whether you averaged their neurocognitive (NC) performance over all domains or picked out specific areas of impairment.
The study, of 560 people with HIV undergoing a randomised controlled trial of protease inhibitor monotherapy, notably failed to find any association between patients' CD4 nadir (their lowest-ever CD4 count) and NC impairment, unlike other studies. It also failed to find any association of NC with being on an ARV regimen without good penetration into the central nervous system (with a low so-called CPE score).
Researcher Alan Winston of Imperial College in London commented that this was probably because this was a study of patients on long-term, stable antiretroviral therapy and thus excluded ones who might be suffering from acute HIV-related cerebral symptoms.
In multivariate analysis, and after accounting for other probable bias, the only factor out of those measured that was associated with worse NC impairment was, in white patients, hepatitis C infection.
This analysis did find that NC impairment was over twice as common in black patients as in white compared to the general population.
Neurocognitive performance in the 'general population', however, depends on studies of groups that may not reflect the HIV-positive population.
Accordingly the researchers did a re-analysis of NC impairment, comparing it to a 'general population' group that was adjusted to take account of studies of impairment in HIV-negative people of black ethnicity – though the few studies that have been done are in African-Americans, not people born in Africa.
By adjusting for the ethnic mix in the patients studied, the researchers found that studies of NC impairment in people with HIV probably, if anything, tended to underestimate its relative prevalence in HIV positive white people (compared to HIV-negative white people) and to overestimate its prevalence in HIV-positive, compared to HIV negative, black people. In an analysis in which NC impairment was defined as a low score in two or more of the five performance areas measured, NC impairment, relative to the adjusted general population, was no worse in black patients than white – but it was, in all people with HIV, three times more common than in the general population according to this measure, and twice as common according to the global score.
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