The study was run in Amsterdam and London and is notable for including closely matched HIV-negative control groups. Results were presented at CROI 2017 in a in a late-breaker poster by James Cole from Imperial College London on behalf of the COBRA collaboration.1
The results are also important because people were following over time and the rates of change related to normal aging was able to be compared between HIV-positive and HIV-negative people with similar background risks. Neurocognitive changes are one of the leading concerns held by HIV-positive people, especially in relation to aging.
In this study, 134 HIV-positive people on ART with undetectable viral load for at least 12 months and a control group of 79 HIV-negative people were enrolled at the Amsterdam Medical Centre and Imperial College London. Retainment in the study was good with follow-up results available for 120/134 HIV-positive and 76/79 HIV-negative participants (at a median of just under two years (1.9 years).
Mean age at baseline was 57 years (SD +/- 7). In the HIV-positive group, the mean CD4 count was strong 646 cells/mm3 (+/- 213) and nadir CD4 showed historical HIV damage 185 (+/- 144) cells/mm3, reflecting a common history shared by many older HIV-positive people. Unfortunately, this was a largely male study, with only nine HIV-positive women and six HIV-negative women.
Neuroimaging was conducted using magnetic resonance imaging (MRI) for multiple regions at baseline and after two years, with changes adjusted for age, time between scans, intracranial volume and the type of scanner. Similar adjusted analysis were produced for neuropsychological assessments.
The main results showed that there were some differences between the two groups at baseline, with the HIV-positive group having slightly smaller grey matter volume (0.65 vs 0.68 L, p=0.02), abnormal white matter microstructure (p<0.01) and poorer cognitive function (in 4/7 functions: attention, processing speed, motor function and global cognitive performance, all p <0.01), compared to the HIV-negative group.
Mean changes between baseline and follow-up found no significant differences in any of the 14 scanning regions, including rate of grey matter loss, or in the 7 neuropsychological functions, and no consistent pattern of change in the positive vs negative groups. Cognitive performance also didn't reduce over time and global cognition score increased in both groups (+0.79 vs +0.45 in HIV positive vs HIV negative, respectively) -- suggesting that there may have been a learning effective from the repeated tests.
The researchers concluded that their analysis found no evidence of accelerated brain aging in HIV-positive people on ART compared to matched HIV-negative controls.
An ongoing analysis is looking for risk factors that can explain the slightly lower baseline results, perhaps related to duration of infection, time before starting ART, nadir CD4 count and lifestyle factors. The results will be just as important as the current study.
Simon Collins is a member of the scientific advisory board for the COBRA collaboration.
These results are reassuring and support another benefit to universal ART that is now recommended in treatment guidelines.
Although the potential factors that might explain the differences between the two groups at baseline were not discussed in the study, the lack of a long-term impact on the rate of further change, even in people who have had low CD4 nadir counts is also encouraging.
It is clearly important for similar research to look at whether results are similar for women, as the low numbers in this study mean it is not powered to show any differences.
Cole JH et al for the COBRA collaboration. Longitudinal analysis shows no evidence for accelerated brain ageing in treated HIV. CROI 2017, 13-16 February 2017, Seattle. Late breaker poster abstract 352LB.
www.croiconference.org/sessions/longitudinal-analysis-shows-no-evidence-accelerated-brain-ageing-treated-hiv (abstract and poster)