Clinical and neuroimaging correlates of cognition in HIV.

This study investigated whether HIV-positive participants, stable on combined antiretroviral therapy (cART), showed cognitive impairments relative to HIV-negative controls; and whether clinical and neuroimaging factors correlated with cognitive function in the HIV-positive participants. One hundred and twenty-six white men who have sex with men, of whom 78 were HIV-positive and stable on cART and 48 were HIV negative, were recruited to this cross-sectional study. The median age of HIV-positive participants in this study was 47. They underwent clinical and neuropsychological evaluation and magnetic resonance imaging of the brain, including diffusion tensor imaging (DTI). Cognitive scores for both groups were compared, and regression models were run to explore the influence of clinical, psychiatric, lifestyle, and neuroimaging variables on cognition. The prevalence of neurocognitive impairment, using the multivariate normative comparison criteria, was 28% in HIV-positive participants and 5% in HIV-negative participants. After covarying for age, years of education, and non-English speaking background, there were significant differences between the HIV group and the controls across four cognitive domains. The HIV group showed significantly higher mean diffusivity (MD) and lower fractional anisotropy (FA) than the control group on DTI. Although anxiety levels were clinically low, anxiety and DTI measures were the only variables to show significant correlations with cognitive function. In the HIV group, poorer cognitive performance was associated with higher MD and lower FA on DTI and higher (albeit clinically mild) levels of anxiety. Our findings suggest that white matter changes and subtle anxiety levels contribute independently to cognitive impairment in HIV.

A Systematic Review of Longitudinal Associations Between Reaction Time Intraindividual Variability and Age-Related Cognitive Decline or Impairment, Dementia, and Mortality.

OBJECTIVES: Intraindividual variability (IIV) in reaction time refers to the trial-to-trial fluctuations in responding across a given cognitive task. Cross-sectional research suggests that IIV increases with normal and neuropathological ageing and it may serve as a marker of neurobiological integrity. This raises the possibility that IIV may also predict future cognitive decline and, indeed, neuropathology. Therefore, we conducted a systematic review to address these issues. METHODS: A search of electronic databases Embase, Medline, PsycINFO, and Web of Science was completed on May 17, 2016 that identified longitudinal investigations of IIV in middle-aged or older adults. RESULTS: A total of 688 studies were initially identified of which 22 met the inclusion criteria. Nine included longitudinal IIV measures and 17 predicted subsequent outcome (cognitive decline or impairment, dementia, mortality) from baseline IIV. The results suggested IIV increased over time, particularly in participants aged over 75 years. Greater baseline IIV was consistently associated with increased risk of adverse outcomes including cognitive decline or impairment, and mortality. CONCLUSIONS: Increased IIV over time is associated with normal ageing. However, further increases in IIV over and above those found in normal ageing may be a risk factor for future cognitive impairment or mortality. Measures of IIV may, therefore, have considerable potential as a supplement to existing clinical assessment to aid identification of individuals at risk of adverse outcomes such as dementia or death. (JINS, 2017, 23, 431-445).

Associations between reaction time measures and white matter hyperintensities in very old age.

In old age, a relationship has been reported between intraindividual variability (IIV) in reaction time and white matter integrity as evidenced by white matter hyperintensities (WMH). However, it is unclear how far such associations are due to incipient neurodegenerative pathology in the samples investigated. The present study examined the relationship between IIV and WMH in older individuals (N=526) drawn from the Sydney Memory and Ageing Study. Using a complex reaction time (RT) task, greater IIV and mean-RT were related to a higher WMH burden in the frontal lobe. Critically, significant associations remained having taken future dementia into account suggesting that they were not explained by incipient dementia. Additionally, independent measures of executive function accounted for the association between RT metrics and WHM. The results are consistent with the view that frontally-supported cognitive processes are involved in IIV-WMH relations, and that RT measures are sensitive to compromise in white matter structures in non-demented older individuals.

Does within-person variability predict errors in healthy adults aged 18-90?

This study investigated within-person variability on basic psychomotor tasks in relation to errors on a higher order cognitive task. We were interested in whether more variable individuals were more prone to making errors, and whether this relationship varied with age. Variability was assessed using simple and choice reaction time, while errors of omission (misses) and commission (false alarms) were obtained from simple and complex visual search tasks. Data from 557 participants aged 18-90 years were included in the analysis. Greater variability was associated with more misses, and distribution analyses showed that slower responses were behind this effect. Variability was also associated with false alarms, but the pattern was inconsistent. Taking age into account revealed that the association between variability and misses in the simple visual search condition was stronger in older (aged 65-90 years) participants. The results suggest the relationship between greater variability and errors of omission (misses) may be related to inattention. Measures of variability may therefore provide valuable insights into individual differences in error rates and, more broadly, may also offer early warning of persons who are more prone to errors in visual search.

Intraindividual Stepping Reaction Time Variability Predicts Falls in Older Adults With Mild Cognitive Impairment.

BACKGROUND: Reaction time measures have considerable potential to aid neuropsychological assessment in a variety of health care settings. One such measure, the intraindividual reaction time variability (IIV), is of particular interest as it is thought to reflect neurobiological disturbance. IIV is associated with a variety of age-related neurological disorders, as well as gait impairment and future falls in older adults. However, although persons diagnosed with Mild Cognitive Impairment (MCI) are at high risk of falling, the association between IIV and prospective falls is unknown. METHODS: We conducted a longitudinal cohort study in cognitively intact (n = 271) and MCI (n = 154) community-dwelling adults aged 70-90 years. IIV was assessed through a variety of measures including simple and choice hand reaction time and choice stepping reaction time tasks (CSRT), the latter administered as a single task and also with a secondary working memory task. RESULTS: Logistic regression did not show an association between IIV on the hand-held tasks and falls. Greater IIV in both CSRT tasks, however, did significantly increase the risk of future falls. This effect was specific to the MCI group, with a stronger effect in persons exhibiting gait, posture, or physiological impairment. CONCLUSIONS: The findings suggest that increased stepping IIV may indicate compromised neural circuitry involved in executive function, gait, and posture in persons with MCI increasing their risk of falling. IIV measures have potential to assess neurobiological disturbance underlying physical and cognitive dysfunction in old age, and aid fall risk assessment and routine care in community and health care settings.

Increased intraindividual reaction time variability in persons with neuropsychiatric manifestations of systemic lupus erythematosus.

Systemic Lupus Erythematosus (SLE) can affect multiple organ systems, including the central (CNS) and/or peripheral nervous system. Individuals with nervous system involvement (termed Neuropsychiatric SLE or NPSLE) can present with nonspecific symptoms such as cognitive dysfunction. It is difficult to ascertain whether this is a direct consequence of lupus disease activity on the brain. Intraindividual variability, measured through trial-to-trial reaction time variation, has been proposed as a behavioral marker of CNS integrity. We compared 14 NPSLE, 20 non-NPSLE, and 27 age-matched healthy participants using multiple variability metrics. Variability was increased in NPSLE compared with non-NPSLE participants, and was increased throughout the distribution rather than there being a selective increase in extreme reaction times. Variability metrics were strongly intercorrelated providing convergent evidence that the different metrics are tapping similar processes. The results suggest that there is ongoing disruption to cognitive processing in NPSLE and may indicate small fluctuations in attention.

mHealth and memory aids: levels of smartphone ownership in patients.

BACKGROUND: The use of mobile devices to deliver healthcare has not yet been exploited in neuropsychological rehabilitation. Smartphones have the potential to serve as multi-functional memory aids. AIMS: To investigate whether patients attending a clinic for mixed memory problems own smartphones, to determine whether this could be a widely applicable medium to use as a memory aids device. METHODS: A questionnaire on smartphone ownership was given to an opportunity sample of consecutive patients attending a neuropsychiatry and memory disorders outpatient clinic. Data were collected in 2012 and repeated 12 months later in 2013 to assess changes over time. RESULTS: Ownership of mobile phones was stable between 2012 (81%) and 2013 (85%), but ownership of smartphones showed a significant increase (from 26% to 40%). Age negatively predicted smartphone ownership. CONCLUSION: Despite cognitive or psychiatric problems, our patient group are as likely to own a mobile phone as a member of the general population. Ownership levels are at 40% and likely to increase in the future. Exploring how smartphones and their apps could function as memory aids is likely to be useful for a large enough number of patients to be clinically worthwhile.