***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background : The frequency of HIV dementia in a recent study of HIV+ individuals at the Infectious Disease Institute in Kampala , Ug and a , was 31 % . Coformulated generic drugs , which include stavudine , are the most common regimens to treat HIV infection in Ug and a and many other parts of Africa . Objective : To evaluate the benefits and risks of stavudine-based highly active antiretroviral therapy ( HAART ) for HIV-associated cognitive impairment and distal sensory neuropathy . The study compared neuropsychological performance changes in HIV+ individuals initiating HAART for 6 months and HIV− individuals receiving no treatment for 6 months . The risk of antiretroviral toxic neuropathy as a result of the initiation of stavudine-based HAART was also examined . Methods : At baseline , 102 HIV+ individuals in Ug and a received  neurologic , neuropsychological , and functional assessment s ; began HAART ; and were followed up for 6 months . Twenty-five HIV− individuals received identical clinical assessment s and were followed up for 6 months . Results : In HIV+ individuals , there was improvement in verbal memory , motor and psychomotor speed , executive thinking , and verbal fluency . After adjusting for differences in sex , HIV+ individuals demonstrated significant improvement in the Color Trails 2 test ( p = 0.025 ) compared with HIV− individuals . Symptoms of neuropathy developed in 38 % of previously asymptomatic HIV+ patients after initiation of the stavudine-based HAART . Conclusions : After the initiation of highly active antiretroviral therapy ( HAART ) including stavudine , HIV+ individuals with cognitive impairment improve significantly as demonstrated by improved performance on a test of executive function . However , peripheral neurotoxicity occurred in 30 patients , presumably because of stavudine-based HAART , suggesting the need for less toxic therapy A study of neuropsychological performance was conducted in 33 HIV+ patients initiating highly active antiretroviral therapy ( HAART ) . Grooved Pegboard ( GP ) non-dominant h and performance improved in 23/33 ( 70 % ) subjects ( P=0.002 ) . Among 23 patients with motor slowing ( GP non-dominant h and z score < -1.0 ) at baseline , 18 ( 78 % ) improved on the GP non-dominant h and test after initiating HAART ( P=0.001 ) . GP non-dominant h and performance improved longitudinally in HIV+ patients initiating HAART , while matched HIV+ controls not on HAART did not change ( P=0.045 ) . Significant improvement in motor performance can occur after HAART in HIV+ patients with impairment Objectives To delineate and compare the nature and frequency of mutations known to confer resistance to HIV-1  nucleoside reverse transcriptase inhibitors in the cerebrospinal fluid ( CSF ) and blood compartments . Methods Fifty-three paired CSF and plasma specimens had been prospect ively collected and stored from 49 HIV-1 infected patients . These were tested using a commercially available line probe assay which allows the simultaneous detection of wild-type and drug selected variants conferring resistance to one or more drugs : zidovudine , didanosine , zalcitabine , and lamivudine . Results Of the 53 ( 58 % ) paired sample s , 31 could be amplified by nested PCR . The current assay 's limitation for use with CSF is highlighted as 91 % of blood sample s amplified compared with 60 % of CSF sample s showing the assays inability to amplify viral loads below 1000 copies/ml . Of the 31 patients 21 ( 68 % ) had identical resistance patterns in the CSF and plasma ; the other 10 ( 32 % ) patients had a resistance profile in the CSF that was different from that in their plasma . Of these , three sample s demonstrated amino acid changes associated with high level zidovudine resistance in the CSF but the blood sample remained genotypically sensitive . Nine sample s demonstrated resistance in blood but remained wild-type in the CSF . Resistant genotypes were detected in CSF for all nucleosides except didanosine . Conclusions Differences in the positions and frequencies of wild-type and drug selected variants in specimens derived from the CSF and blood compartments were detected in a significant number of patients ; this argues for the independent development of drug resistance in the CNS in some patients . These findings may have important implication s in guiding antiretroviral therapy in HIV-1 infection Objectives : This study examined the effects of HAART on neurocognitive functioning in persons with hepatitis C virus ( HCV ) and HIV co-infection . Design : A prospect i ve study examining neurocognitive performance before and after HAART initiation . Method : Participant groups included a mono-infected group ( 45 HIV+/HCV− participants ) and a co-infected group ( 20 HIV+/HCV+ participants ) . A neuropsychological battery ( attention/concentration , psychomotor speed , executive functioning , verbal memory , visual memory , fine motor , and gross motor functioning ) was used to evaluate all participants . After 6 months of HAART , 31 HIV+ mono-infected and 13 HCV+/HIV+ co-infected participants were reevaluated . Results : Neurocognitive functioning by domain revealed significantly worse performance in the co-infected group when compared to the monoinfected group on domains of visual memory and fine motor functioning . Assessment of neurocognitive functioning after antiretroviral therapy revealed that the co-infected group was no longer performing worse than the monoinfected group . Conclusions : The findings of the current study suggest that persons with HCV+/HIV+ co-infection may have greater neurocognitive declines than persons with HIV infection alone . HCV+/HIV+ co-infection may accelerate the progression of HIV related neurocognitive decline Objectives : HAART suppresses HIV viral replication and restores immune function . The effects of HAART on neurological disease are less well understood . The aim of this study was to assess the prevalence and incidence of  neurocognitive impairment in individuals who initiated HAART as part of an AIDS clinical trial . Design : A prospect i ve cohort study of HIV-positive patients enrolled in r and omized antiretroviral trials , the AIDS Clinical Trials Group ( ACTG ) Longitudinal Linked R and omized Trials ( ALLRT ) study . Methods : We examined the association between baseline and demographic characteristics and neurocognitive impairment among 1160 subjects enrolled in the ALLRT study . Results : A history of immunosuppression ( nadir CD4 cell count < 200 cells/μl ) was associated with an increase in prevalent neurocognitive impairment . There were no significant virological and immunological predictors of incident neurocognitive impairment . Current immune status ( low CD4 cell count ) was associated with sustained prevalent impairment . Conclusion : The association of previous advanced immunosuppression with prevalent and sustained impairment suggests that there is a non-reversible component of neural injury that tracks with a history of disease progression . The association of sustained impairment with worse current immune status ( low CD4 cell count ) suggests that restoring immunocompetence increases the likelihood of neurocognitive recovery . Finally , the lack of association between incident neurocognitive impairment and virological and immunological indicators implies that neural injury continues in some patients regardless of the success of antiretroviral therapy on these laboratory measures Objective : To rigorously evaluate the time course of cognitive change in a cohort of individuals with HIV-associated neurocognitive disorders ( H AND ) initiating combination antiretroviral therapy ( CART )  , and to investigate which demographic , laboratory , and treatment factors are associated with neuropsychological ( NP ) outcome ( or “ any NP improvement ” ) . Methods : Study participants included 37 HIV+ individuals with mild to moderate NP impairment who initiated CART and underwent NP testing at 12 , 24 , 36 , and 48 weeks thereafter .  NP change was assessed using a regression-based change score that was normed on a separate NP-stable group thereby controlling for regression toward the mean and practice effect . Mixed-effect regression models adjusting for loss to follow-up were used to evaluate the time course of cognitive change and its association with baseline and time-varying predictors . Results : In persons with H AND initiating CART , cognitive improvement happens soon after initiation ( 13 % at week 12 ) , but more often 24 , 36 , and up to 48 weeks after initiation ( up to 41 % ) , with fewer than 5 % demonstrating significant worsening . In multivariate analyses , unique predictors of NP improvement included more severe baseline NP impairment and higher CART CNS penetration index . Greater viral load decrease was associated with NP improvement only in univariate analyses . Conclusion : Clinical ly meaningful neuropsychological improvement seemed to peak around 24–36 weeks after combination antiretroviral therapy initiation and was prolonged over the 1-year study period . This study also provides new evidence that benefit may be maximized by choosing antiretroviral medications that reach therapeutic concentrations in the CNS At least 10 different genetic human immunodeficiency virus type 1 ( HIV-1 ) subtypes ( A-J ) are responsible for the AIDS p and emic . Much of the underst and ing of HIV-1 disease progression derives from studies in the developed world where HIV infection is almost exclusively subtype B. This has led many to question whether the properties and consequences of HIV-1 infection can be generalized across subtypes that afflict the majority of infected persons in the developing world . From 1985 to 1997 , a prospect i ve study of registered female sex workers in Senegal tracked the introduction and spread of HIV-1 subtypes A , C , D , and G. In clinical follow-up , the AIDS-free survival curves differed by HIV-1 subtype . Women infected with a non-A subtype were 8 times more likely to develop AIDS than were those infected with subtype A ( hazard ratio=8.23 ; P=. 009 ) , the predominant subtype in the study . These data suggest that HIV-1 subtypes may differ in rates of progression to AIDS Summary : Although the effects of highly active antiretroviral therapy ( HAART ) have result ed in substantial improvements in the systemic health of patients with HIV infection , concerns remain that these medications , which cross the blood – brain barrier poorly , may have a less beneficial effect on nervous system function . This raises the possibility that there may be a progressive long-term decline in neurologic function in patients with adequate systemic response . In a prospect i ve longitudinal study , subjects were evaluated immediately before instituting HAART . Forty-eight subjects underwent  ultrasensitive HIV RNA quantitative evaluation of both plasma and cerebrospinal fluid as well as neurologic and neuropsychological examinations .  They were reevaluated 6 months after treatment initiation while receiving stable HAART . Both plasma and cerebrospinal fluid viral levels significantly declined after treatment . There was significant improvement in neurologic and neuropsychological functioning after HAART . These results indicate that despite the poor central nervous system penetration of most of these agents , there is satisfactory short-term improvement in both central nervous system viral burden and nervous system function with HAART . However , because treatment failure is increasingly likely over time , continued longitudinal evaluation of this group of subjects is required Interpretations of longitudinal studies of cognitive aging are misleading unless effects of practice and selective drop-out are considered . A r and om effects model taking practice and drop-out into account analyzed data from four successive presentations of each of two intelligence tests , two vocabulary tests , and two verbal memory tests during a 17-year longitudinal study of 5,899 community residents whose ages ranged from 49 to 92 years . On intelligence tests , substantial practice effects counteracted true declines observed over 3 to 5 years of aging and remained significant even with intervals of 7 years between successive assessment s. Adjustment for practice and drop-out revealed accelerating declines in fluid intelligence and cumulative learning , linear declines in verbal free recall , and no substantial change in vocabulary . Socioeconomic status and basal levels of general fluid ability did not affect rates of decline . After further adjustment for demographics , variability between individuals was seen to increase as the sample aged Nucleoside reverse transcriptase inhibitors ( NRTIs ) suppress human immunodeficiency virus ( HIV ) replication , but are often associated with mitochondrial toxicity . Although well studied outside of the central nervous system , no investigation has examined the effects of these drugs on brain mitochondria of individuals living with HIV . The authors used proton magnetic resonance spectroscopy to evaluate NRTI-related changes in brain mitochondria . N-acetylaspartate ( NAA ; sensitive to alterations in mitochondrial integrity ) was measured in frontal lobe white and gray matter of 18 HIV+ individuals taking didanosine and /or stavudine ( two NRTIs likely to cause mitochondrial toxicity ) , 14 HIV+ individuals taking zidovudine and lamivudine , 16 HIV+ individuals not currently taking antiretrovirals , and 17 HIV− controls . The HIV+ groups were comparable on demographic measures , estimates of illness severity , and estimated length of HIV infection . Those taking didanosine and /or stavudine had a significant 11.4 % decrease in concentrations of frontal white matter NAA compared to HIV− controls , whereas NAA levels of the other HIV+ groups were intermediate . Group differences in metabolites were not found in front 
    Output:
    
The results show that although HAART does improve cognition , it does not appear to fully eradicate impairments .