In this study we report a high prevalence of a positive screen for dementia using the IHDS with more than half of participants on ART in Bamenda screening positive. We also show that the primary function that appears impaired, based on this screening tool, is psychomotor speed while motor speed and memory recall are relatively better preserved. Few predictors of poor neurocognitive function were identified, with HIV-symptomatology being the strongest and the others being marital status and level of education.
To the best of our knowledge this is one of the few studies documenting and characterising the type of neurocognitive disorders in patients already on antiretrovirals in sub-Saharan Africa. Our positive screen prevalence estimate is very much higher than the 21% reported by Njamnshi et al., in HIV-positive patients in Yaounde, Cameron . Our estimate is however very similar to the 80% reported by Robbins et al., in a population of patients on ART in South Africa . Other studies conducted in Africa indicated lower screen positive rates: 22% in ART naïve patients in Lusaka, Zambia ; 14% in a mix of ART-naïve and experienced patients in Blantyre, Malawi (13.4% in patients on ART for at least six months) ; 38% in HIV-positive patients in Gaborone, Botswana (97.5% of whom were ART-experienced) .
It is not immediately clear to us why such a high positive screen rate was recorded. However, amongst others, we suspect that this could be an indication of a truly high prevalence of neurocognitive disorders in these patients who were already on antiretroviral therapy, an indication of relatively advanced HIV-disease. It is worthwhile noting that in this setting antiretroviral therapy was only recommended in patients with CD4+ counts less than 200 or having an AIDS-defining illness (WHO stage IV).
The high screen positive rate could also potentially be due to the IHDS performing poorly (with a low specificity thus high false positivity rate) in this population. This poor performance could be linked to the use of antiretroviral therapy some of which are known to cause peripheral neuropathy which could potentially reduce psychomotor speed. It is worthwhile noting that a vast majority of the patients in this clinic were on non-nucleotide reverse transcriptase inhibitor (NNRTI)-based antiretroviral therapy, with the NNRTI being combined with two nucleotide-based reverse transcriptase inhibitors (NRTI). Zidovudine and lamivudine are the most commonly used NRTI and have been shown to have neurologic side-effects that include peripheral neuropathy . Efavirenz is also commonly used and has been shown to have CNS effects .
The poor performance by the IHDS could also be linked to the education status of participants. In an analysis of the performance of IHDS, Waldrop-Valverde et al., showed that only education was significantly associated with performance . Further, a study by Nitrini et al., showed that performance on the AHS was inversely correlated with the number of years of schooling . We note however that Sacktor et al. found no effect of educational level on the performance of the IHDS .
Though widely used, further studies are needed to validate the IHDS particularly in a large sample of patients on antiretroviral therapy and moderate to low education status [18, 20, 21]. This validation is particularly important as other authors have reported that certain screening tests may not be appropriate in certain populations. For example Robbins et al. in their assessment of the utility of the Montreal Cognitive Assessment scale reported that it may need to be modified before being used in South Africa .
Few studies have examined correlates of neurocognitive disorders in patients on ART. Lawler et al.  identified level of education and age (and not CD4 count) as significant correlates of disorders in patients in Botswana. Patel et al. identified male gender and education level as risk factors associated with neurocognitive disorders. Joska et al. also confirmed older age and low education level as factors associated with HAND in South Africa . Njamnshi et al.  reported advanced clinical diseases, low CD4 counts and low haemoglobin levels as risk factors for HAND in HIV-positive subjects in Yaounde, Cameroon. The latter findings are consistent with our findings of positive screen being correlated with increased HIV-symptomatology, indicative of relatively advanced disease.
While validity of our findings is vouched, amongst others, by the use of a well-trained health personnel in administering the IHDS, the use of a calm and re-assuring milieu while assessing the participants, the adequately large sample size of participants on antiretroviral therapy, and controlling for some confounding in the assessment of correlates, a number of limitations need to be considered in interpreting these data. First, the study is based on a screening tool, not a diagnostic tool – we did not systematically perform a diagnostic assessment and some of the positive screens could effectively be false positives. This limitation leads one to argue for a better assessment of not only the validity of the IHDS as a tool for screening for dementia in this population, but also for further prospective studies that evaluate the long-term evolution of patients who at some point screen positive for HAND. Only then will it be possible to make a recommendation on the utility, or lack thereof, of systematically screening in this population using the IHDS.
Other limitations include the lack of detailed information on HIV-disease such as CD4+ cell count levels and HIV-viral load at the time of study enrolment. However, the fact that these patients were on antiretroviral therapy and the high prevalence of symptoms suggest that the participants must have had advanced HIV-disease. The findings are certainly only representative of patients on antiretroviral therapy attending HIV-clinics like that of the Bamenda Regional Hospital. Some potential predictors could also have been missed as not all characteristics were assessed. The latter could also imply a limit on the adjustment for unmeasured confounders such as HIV-viral load.