Neuropsychological screening for cognitive impairment using computer-assisted tasks

Prenatal exposure to mixtures of per- and polyfluoroalkyl substances and organochlorines affects cognition in adolescence independent of postnatal exposure

BACKGROUND

Studies on cognitive and neurodevelopmental outcomes have shown inconsistent results regarding the association with prenatal exposure to perfluoroalkyl substance (PFAS) and organochlorines. Assessment of mixture effects of correlated chemical exposures that persist in later life may contribute to the unbiased evaluation and understanding of dose-response associations in real-life exposures.

METHODS

For a subset of the 4th Flemish Environment and Health Study (FLEHS), concentrations of four PFAS and six organochlorines were measured in respectively 99 and 153-160 cord plasma samples and 15 years later in adolescents' peripheral serum by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry (UPLC-MS/MS). Sustained and selective attention were measured at 14-15 years with the Continuous Performance Test (CPT) and Stroop Test as indicators of potential neurodevelopmental deficits. Quantile g-computation was applied to assess the joint associations between prenatal exposure to separate and combined groups of PFAS and organochlorines and performance in the CPT and Stroop Test at adolescence. Subsequently, individual effects of each chemical compound were analyzed in mixed effects models with two sets of covariates. Analytical data at birth and at the time of cognitive assessment allowed for off-setting postnatal exposure.

RESULTS

In mixtures analysis, a simultaneous one-quantile increase in the natural log-transformed values of PFAS and organochlorines combined was associated with a decrease in the mean reaction time (RT) and the reaction time variability (RTV) in the CPT (β = -15.54, 95% CI:-29.64, -1.45, and β = -7.82, 95% CI: -14.97, -0.67 respectively) and for the mixture of PFAS alone with RT (β = -11.94, 95% CI: -23.29, -0.60). In the single pollutant models, these results were confirmed for the association between perfluorohexanesulfonate (PFHxS) with RT (β = -17.95, 95% CI = -33.35, -2.69) and hexachlorobenzene with RTV in the CPT (β = -5.78, 95% CI: -10.39, -0.76). Furthermore, the participants with prenatal exposure above the limit of quantification for perfluorononanoic acid (PFNA) had a significantly shorter RT and RTV in the CPT (β = -23.38, 95% CI: -41.55, -5.94, and β = -9.54, 95% CI: -19.75, -0.43, respectively).

CONCLUSION

Higher prenatal exposure to a PFAS mixture and a mixture of PFAS and organochlorines combined was associated with better sustained and selective attention during adolescence. The associations seemed to be driven by PFHxS and were not linked to exposure levels at the time of assessment.

Exposure to greenspace and bluespace and cognitive functioning in children - A systematic review

BACKGROUND

The field of greenspace and bluespace research in relation to cognitive outcomes is rapidly growing. Several systematic reviews have already been published on this topic but none of them are specific to cognitive outcomes in the entire age range of children. Moreover, only a few of them have examined the effects of bluespace in addition to greenspace. Also, theses reviews are focused either only on observational studies or experimental studies. Our systematic review focuses on cognitive outcomes in relation to greenspace and bluespace in children and adolescents aged 0-18; it captures both observational and experimental studies. Cognitive outcomes are presented according to an evidence-based taxonomy of human cognitive abilities: the Cattell-Horn-Carroll (CHC) theory.

METHODS

We conducted searches in the PubMed and PsychInfo databases, from their inception dates to 17 December 2021. We used three-text terms related to outcome, exposure, and population as well as MeSH terms for outcome and population. Further, the reference lists and existing reviews were searched ("snowball" search) until 21 April 2022 to detect additional studies. For the results reporting, we followed the updated guidelines of the Preferred Reporting Items for Systematic reviews and Meta Analyses (PRISMA). We included observational and experimental studies on greenspace or bluespace exposure in relation to cognitive functioning, published in English, German, or Polish. Two reviewers independently checked study eligibility and extracted data. Two reviewers evaluated the risk of bias according to the Office of Health Assessment and Translation (OHAT) tool. At all stages, discrepancies between the two reviewers were solved via discussion with a third reviewer.

RESULTS

Records identified from PubMed (n = 2030) and PsycINFO (n = 1168) were deduplicated and screened. Twenty one reports were first selected. The "snowball" search revealed 16 additional reports. Altogether, 39 studies (17 experimental and 22 observational) published in 37 reports were qualified. The data extraction showed that the methodology used in the studies was heterogenous and the findings were inconsistent. The majority of the studies investigated attentional functioning, which we subdivided into two categories according to the CHC theory: attentional control and reaction and decision speed (12 studies) and attentional control and processing speed (10 studies). Eleven studies investigated working memory and/or short-term memory that we categorized as CHC working memory capacity. Nine studies investigated intellectual functioning, which we categorized as CHC general ability, fluid reasoning, and comprehension-knowledge. Two studies investigated visual-spatial skills, which we categorized as CHC visual processing and psychomotor speed. One study measured parent-reported attention; two studies examined early childhood/cognitive development; three studies examined decision-making and self-regulation, which can be categorized as several CHC theory abilities.

DISCUSSION

The heterogeneity of the included studies does not permit clear conclusions for our review. In accordance with previous systematic reviews, greenspace and bluespace were not more strongly related to a particular domain of cognitive functioning than other cognitive domains, and no effects of age or type of exposure assessment on the association between nature and cognition were detected. Further research is needed, including state-of-the-art of assessment of cognitive outcomes and diverse exposure assessment methods within both observational and experimental approaches. Expertise will be required in several domains, such as environmental epidemiology, cognitive psychology, and neuropsychology. Systematic review registration number (INPLASY): 202220018.

Residential green space improves cognitive performances in primary schoolchildren independent of traffic-related air pollution exposure

BACKGROUND

Cognitive performances of schoolchildren have been adversely associated with both recent and chronic exposure to ambient air pollution at the residence. In addition, growing evidence indicates that exposure to green space is associated with a wide range of health benefits. Therefore, we aimed to investigate if surrounding green space at the residence improves cognitive performance of primary schoolchildren while taking into account air pollution exposure.

METHODS

Cognitive performance tests were administered repeatedly to a total of 307 primary schoolchildren aged 9-12y, living in Flanders, Belgium (2012-2014). These tests covered three cognitive domains: attention (Stroop and Continuous Performance Tests), short-term memory (Digit Span Forward and Backward Tests), and visual information processing speed (Digit-Symbol and Pattern Comparison Tests). Green space exposure was estimated within several radii around their current residence (50 m to 2000 m), using a aerial photo-derived high-resolution (1 m²) land cover map. Furthermore, air pollution exposure to PM_2.5 and NO₂ during the year before examination was modelled for the child's residence using a spatial-temporal interpolation method.

RESULTS

An improvement of the children's attention was found with more residential green space exposure independent of traffic-related air pollution. For an interquartile range increment (21%) of green space within 100 m of the residence, a significantly lower mean reaction time was observed independent of NO₂ for both the sustained-selective (-9.74 ms, 95% CI: -16.6 to -2.9 ms, p = 0.006) and the selective attention outcomes (-65.90 ms, 95% CI: -117.0 to -14.8 ms, p = 0.01). Moreover, green space exposure within a large radius (2000 m) around the residence was significantly associated with a better performance in short-term memory (Digit-Span Forward Test) and a higher visual information processing speed (Pattern Comparison Test), taking into account traffic-related exposure. However, all associations were attenuated after taking into account long-term residential PM_2.5 exposure.

CONCLUSIONS

Our panel study showed that exposure to residential surrounding green space was associated with better cognitive performances at 9-12 years of age, taking into account traffic-related air pollution exposure. These findings support the necessity to build attractive green spaces in the residential environment to promote healthy cognitive development in children.

Public and occupational health risks related to lead exposure updated according to present-day blood lead levels

Lead is an environmental hazard that should be addressed worldwide. Over time, human lead exposure in the western world has decreased drastically to levels comparable to those among humans living in the preindustrial era, who were mainly exposed to natural sources of lead. To re-evaluate the potential health risks associated with present-day lead exposure, a two-pronged approach was applied. First, recently published population metrics describing the adverse health effects associated with lead exposure at the population level were critically assessed. Next, the key results of the Study for Promotion of Health in Recycling Lead (SPHERL; NCT02243904) were summarized and put in perspective with those of the published population metrics. To our knowledge, SPHERL is the first prospective study that accounted for interindividual variability between people with respect to their vulnerability to the toxic effects of lead exposure by assessing the participants' health status before and after occupational lead exposure. The overall conclusion of this comprehensive review is that mainstream ideas about the public and occupational health risks related to lead exposure urgently need to be updated because a large portion of the available literature became obsolete given the sharp decrease in exposure levels over the past 40 years.

Higher surrounding green space is associated with better attention in Flemish adolescents

INTRODUCTION

Previous studies suggested that green space is beneficial for the cognitive development in children. However, evidence in adolescents is limited. Therefore, we aim to investigate green space exposure in association with attention and behaviour in adolescents.

METHODS

This study includes 596 Flemish adolescents between 13 and 17 years old. Attention was assessed with Stroop Test (selective attention) and Continuous Performance Test (sustained and selective attention). Behaviour was determined based on the Strengths and Difficulties Questionnaire. Green space was estimated in several radius distances around their current residence and school based on high-resolution land cover data. Multilevel regression analyses were used adjusting for participant's age, sex, education level of the mother, and area deprivation index.

RESULTS

Surrounding green space in a 2000 m radius is associated with a faster reaction time in adolescents. An IQR (13%) increment in total green space within 2000 m of the residence and school combined, is associated with a 32.7 ms (95% CI: -58.9 to -6.5; p = 0.02) and a 7.28 ms (95% CI: -11.7 to -2.8; p = 0.001) shorter mean reaction time between the presentation of a stimulus and the response based on the Stroop Test and the Continuous Performance Test. Subdividing green space based on vegetation height, shows that green space higher than 3 m is associated with a faster reaction time of the Continuous Performance Test (-6.50 ms; 95% CI: -10.9 to -2.2; p = 0.004), while low green is not. We did not find an association between green space and behavioural development in adolescents.

CONCLUSIONS

Our study shows that green space, especially trees, surrounding the residence and school combined is associated with better sustained and selected attention in adolescents. These findings indicate that the availability of green is important for adolescents that are growing up in a rapidly urbanizing world.

Introducing nature at the work floor: A nature-based intervention to reduce stress and improve cognitive performance

BACKGROUND

Although a growing body of research has shown that exposure to nature has restorative effects on human health, the potential beneficial effects of nature-based interventions in the working environment are still underexplored.

METHODS

We performed a randomized controlled study with a nature-based program during working hours. We enrolled employees, randomized the participants into two groups being an intervention and a control group. Twice a week for three consecutive weeks, the intervention group participated in nature-based activities for 2 h. The primary outcomes were cognitive performance, burnout assessment, salivary cortisol levels, and continuous stress levels. We performed intervention-response analyses using mixed-effects models that included random effects for each participant across the different examinations.

RESULTS

Compared to the control group (n = 20), the intervention group (n = 25) participating in the nature-based program had a lower Burnout Assessment Tool score (-14.9% CI-16.2 to -14.3, difference; p < 0.001), lower salivary cortisol levels (-29.3% CI-34.7 to -25.3; p < 0.001) and higher visual information processing speed (7.4% CI6.9-8.0; p < 0.001). Selective attention of the participants that participated in the nature-based program improved during the interventions (-10.6 CI-19.6 to -6.9, p = 0.045), compared to the controls.

CONCLUSIONS

This study provides novel evidence that exposure to nature during work hours reduces stress and improves cognitive performance. The trial is registered with ClinicalTrials.gov, number: NCT04111796.

Two-year neurocognitive responses to first occupational lead exposure

Objectives Lead exposure causes neurocognitive dysfunction in children, but its association with neurocognition in adults at current occupational exposure levels is uncertain mainly due to the lack of longitudinal studies. In the Study for Promotion of Health in Recycling Lead (NCT02243904), we assessed the two-year responses of neurocognitive function among workers without previous known occupational exposure newly hired at lead recycling plants. Methods Workers completed the digit-symbol test (DST) and Stroop test (ST) at baseline and annual follow-up visits. Blood lead (BL) was measured by inductively coupled plasma mass spectrometry (detection limit 0.5 µg/dL). Statistical methods included multivariable-adjusted mixed models with participants modelled as random effect. Results DST was administered to 260 participants (11.9% women; 46.9%/45.0% whites/Hispanics; mean age 29.4 years) and ST to 168 participants. Geometric means were 3.97 and 4.13 µg/dL for baseline BL, and 3.30 and 3.44 for the last-follow-up-to-baseline BL ratio in DST and ST cohorts, respectively. In partially adjusted models, a doubling of the BL ratio was associated with a 0.66% [95% confidence interval (CI) 0.03-1.30; P=0.040] increase in latency time (DST) and a 0.35% (95% CI ‑1.63-1.63; P=0.59) decrease in the inference effect (ST). In fully adjusted models, none of the associations of the changes in the DST and ST test results with the blood lead changes reached statistical significance (P≥0.12). Conclusions An over 3-fold increase in blood lead over two years of occupational exposure was not associated with a relevant decline in cognitive performance.

Absence of neurotoxicity and lack of neurobehavioral consequences due to exposure to tetrabromobisphenol A (TBBPA) exposure in humans, animals and zebrafish

Tetrabromobisphenol A (2,2',6,6'-tetrabromo-4,4'-isopropylidenediphenol, CAS no. 79-94-7) (TBBPA) is an effective brominated flame retardant present in many consumer products whose effectiveness is attributable to its ability to retard flames and consequently save human lives. Toxicokinetic studies revealed that TBBPA when absorbed via the gastrointestinal tract is rapidly metabolized to glucuronide or sulfate metabolites which are rapidly eliminated by the kidney. TBBPA does not accumulate in the body and there is no evidence that the parent compound is present in the brain. Although this brominated flame retardant was detected in human breast milk and serum, there was no evidence that TBBPA reached the brain in in vivo animal studies as reflected by the absence of neuropathological, neurotoxic, or behavioral alterations indicating that the central nervous system is not a target tissue. These animal investigations were further supported by use of the larval/embryo observations that TBBPA did not produce behavioral changes in a larval/embryo zebrafish a model of chemical-induced neurotoxicity. Although some protein expressions were increased, deceased or not affected in the blood-brain barrier indicating no evidence that TBBPA entered the brain, the changes were contradictory, or gender related, and behavior was not affected supporting that this compound was not neurotoxic. Taken together, TBBPA does not appear to target the brain and is not considered as a neurotoxicant.

A systematic review of the next-day effects of heavy alcohol consumption on cognitive performance

BACKGROUND AND AIMS

Studies examining the next-day cognitive effects of heavy alcohol consumption have produced mixed findings, which may reflect inconsistencies in definitions of 'hangover'. Recent consensus has defined hangover as 'mental and physical symptoms, experienced the day after a single episode of heavy drinking, starting when blood alcohol concentration (BAC) approaches zero'. In light of this, we aimed to review the literature systematically to evaluate and estimate mean effect sizes of the next-day effects of heavy alcohol consumption on cognition.

METHODS

Embase, PubMed and PsycNET databases were searched between December 2016 and May 2018 using terms based on 'alcohol' and 'hangover'. Studies of experimental designs which reported the next-day cognitive effects of heavy alcohol consumption in a 'hangover' group with BAC < 0.02% were reviewed. A total of 805 articles were identified. Thirty-nine full-text articles were screened by two independent reviewers and 19 included in the systematic review; 11 articles provided sufficient data to be included in the meta-analysis; 1163 participants across 19 studies conducted since 1970 were included in the analysis. Data for study design, hangover severity, BAC at testing and cognitive performance were extracted and effect estimates calculated.

RESULTS

The systematic review suggested that sustained attention and driving abilities were impaired during hangover. Mixed results were observed for: psychomotor skills, short- (STM) and long-term memory (LTM) and divided attention. The meta-analysis revealed evidence of impairments in STM [g = 0.64, 95% confidence interval (CI) = 0.15-1.13], LTM (Hedges' g = 0.59, 95% CI = 0.01-1.17) sustained attention (g = 0.47, 95% CI = 0.07-0.87) and psychomotor speed (Hedges' g = 0.66, 95% CI = 0.31-1.00) during alcohol hangover.

CONCLUSION

The research literature suggests that alcohol hangovers may involve impaired cognitive functions and performance of everyday tasks such as driving.

Validation of ANAM for cognitive screening in a mixed clinical sample

The Automated Neuropsychological Assessment Metrics (ANAM) is a library of computer based tests designed to measure cognitive function at a single time-point or longitudinally for detection of cognitive change. This study sought to validate ANAM as a cognitive screening tool for presence of confirmed neuropsychological diagnosis in an outpatient setting. Retrospective data analysis was conducted for 139 patients referred for outpatient neuropsychological assessment. Clinical diagnosis was made independent of ANAM test results and resulted in a diagnostic mix of both neurologic and psychologic etiologies. ANAM scores predictive of presence of confirmed diagnosis were identified using multiple logistic regression and the predictive ability of the resulting model was quantified using receiver operator characteristic analysis. Sensitivity and specificity for the ANAM when combined with anger and depressive symptom scores were 71% and 91%, respectively, with a positive predictive value of 97.5 and negative predictive value of 40.4. This combined approach provided the greatest accuracy for individual tests as well as the composite score of the ANAM in identifying those who received a subsequent clinical diagnosis. Although data should be replicated in larger samples, these results suggest that ANAM may have predictive value and may be a useful screening tool for identifying those who would likely benefit from neuropsychological services.

Urinary t,t-muconic acid as a proxy-biomarker of car exhaust and neurobehavioral performance in 15-year olds

INTRODUCTION

Traffic-related air pollution has been shown to induce neurotoxicity in rodents. Several recent epidemiological studies reported negative associations between residential outdoor air pollution and neurobehavioral performance. We investigated in a population of non-smoker adolescents the associations between the urinary concentration of trans, trans-muconic acid (t,t-MA-U), a metabolite of benzene and used as proxy-biomarker of traffic exposure, and two neurobehavioral domains, i.e. sustained attention and short-term memory.

METHODS

In the framework of an environmental health surveillance study in Flanders (Belgium), we examined between 2008 and 2014 grade nine high school students (n=895). We used reaction time, number of omission errors, and number of commission errors in the Continuous Performance Test to evaluate sustained attention, and for the evaluation of short-term memory we used maximum digit span forward and backward of the Digit Span Test. We measured blood lead (PbB) to assess the independent effect of t,t-MA-U on neurobehavioral outcomes.

RESULTS

This neurobehavioral examination study showed that a ten-fold increase in t,t-MA-U was associated with a 0.14 SD lower sustained attention (95% Confidence Interval: -0.26 to -0.019; p=0.02) and a 0.17 SD diminished short-term memory (95% CI: -0.31 to -0.030; p=0.02). For the same increment in t,t-MA-U, the Continuous Performance Test showed a 12.2ms higher mean reaction time (95% CI: 4.86-19.5; p=0.001) and 0.51 more numbers of errors of omission (95% CI: 0.057-0.97; p=0.028), while no significant association was found with errors of commission. For the Digit Span Tests, the maximum digit span forward was associated with a 0.20 lower number of digits (95% CI: -0.38 to -0.026; p=0.025) and maximum digit span backward with -0.15 digits (95% CI: -0.32 to 0.022; p=0.088). These associations were independent of PbB, parental education and other important covariates including gender, age, passive smoking, ethnicity, urinary creatinine, time of the day, and examination day of the week. For PbB, an independent association was only found with mean reaction time of the Continuous Performance Test (19.1ms, 95% CI: 2.43-35.8; p=0.025).

CONCLUSIONS

In adolescents, a ten-fold increase in the concentration of t,t-MA-U, used as a proxy-biomarker for traffic-related exposure, was associated with a significant deficit in sustained attention and short-term memory. The public health implications of this finding cannot be overlooked as the effect-size for these neurobehavioral domains was about 40% of the effect-size of parental education.

Recent versus chronic exposure to particulate matter air pollution in association with neurobehavioral performance in a panel study of primary schoolchildren

Children's neuropsychological abilities are in a developmental stage. Recent air pollution exposure and neurobehavioral performance are scarcely studied. In a panel study, we repeatedly administered to each child the following neurobehavioral tests: Stroop Test (selective attention) and Continuous Performance Test (sustained attention), Digit Span Forward and Backward Tests (short-term memory), and Digit-Symbol and Pattern Comparison Tests (visual information processing speed). At school, recent inside classroom particulate matter ≤2.5 or 10μm exposure (PM2.5, PM10) was monitored on each examination day. At the child's residence, recent (same day up to 2days before) and chronic (365days before examination) exposures to PM2.5, PM10 and black carbon (BC) were modeled. Repeated neurobehavioral test performances (n=894) of the children (n=310) reflected slower Stroop Test (p=0.05) and Digit-Symbol Test (p=0.01) performances with increasing recent inside classroom PM2.5 exposure. An interquartile range (IQR) increment in recent residential outdoor PM2.5 exposure was associated with an increase in average latency of 0.087s (SE: ±0.034; p=0.01) in the Pattern Comparison Test. Regarding chronic exposure at residence, an IQR increment of PM2.5 exposure was associated with slower performances in the Continuous Performance (9.45±3.47msec; p=0.007) and Stroop Tests (59.9±26.5msec; p=0.02). Similar results were obtained for PM10 exposure. In essence, we showed differential neurobehavioral changes robustly and adversely associated with recent or chronic ambient exposure to PM air pollution at residence, i.e., with recent exposure for visual information processing speed (Pattern Comparison Test) and with chronic exposure for sustained and selective attention.

Solvent exposure and cognitive function in automotive technicians

Automotive technicians are commonly exposed to organic and chlorinated solvents, particularly through use of cleaning products. Occupational solvent exposures have been associated with deficits in cognitive function but, to our knowledge, no previous studies have investigated automotive technicians. The purpose of the present study was to investigate whether previous exposures to n-hexane, in particular, or general solvents posed a persistent neurotoxic hazard to automotive workers. Enrolled in the study were 830 San Francisco Bay Area automotive repair workers. Each participant underwent a battery of cognitive function tests to investigate central nervous system impairment, with a primary focus on the domains of psychomotor speed, fine motor function, memory and mood. Cognitive test results regressed against estimated hexane and total solvent exposures showed little evidence of associations. Exposures to both solvents and hexane were well below the occupational exposure limits. Our results provide some reassurance about persistent neuropsychological effects in automotive workers who use solvent-based products and those who previously used hexane-containing automotive cleaning products, since this solvent is believed no longer to be used in automotive cleaning products. The lack of observed effect in this study may be attributable to low exposures, or it may reflect improved cognitive function since hexane use in automotive cleaning products was discontinued. However, impacts on results of exposure misclassification and/or the healthy worker survivor effect cannot be discounted. Irrespective of the outcome of this study, the main known neurologic effect of n-hexane is peripheral neuropathy, and such an association in automotive technicians is not excluded by these results.

Neurobehavioral performance in adolescents is inversely associated with traffic exposure

On the basis of animal research and epidemiological studies in children and elderly there is a growing concern that traffic exposure may affect the brain. The aim of our study was to investigate the association between traffic exposure and neurobehavioral performance in adolescents. We examined 606 adolescents. To model the exposure, we constructed a traffic exposure factor based on a biomarker of benzene (urinary trans,trans-muconic acid) and the amount of contact with traffic preceding the neurobehavioral examination (using distance-weighted traffic density and time spent in traffic). We used a Bayesian structural equation model to investigate the association between traffic exposure and three neurobehavioral domains: sustained attention, short-term memory, and manual motor speed. A one standard deviation increase in traffic exposure was associated with a 0.26 standard deviation decrease in sustained attention (95% credible interval: -0.02 to -0.51), adjusting for gender, age, smoking, passive smoking, level of education of the mother, socioeconomic status, time of the day, and day of the week. The associations between traffic exposure and the other neurobehavioral domains studied had the same direction but did not reach the level of statistical significance. The results remained consistent in the sensitivity analysis excluding smokers and passive smokers. The inverse association between sustained attention and traffic exposure was independent of the blood lead level. Our study in adolescents supports the recent findings in children and elderly suggesting that traffic exposure adversely affects the neurobehavioral function.

Chronic ambient hydrogen sulfide exposure and cognitive function

BACKGROUND

Exposures to hydrogen sulfide gas (H2S) have been inconclusively linked to a variety of negative cognitive outcomes. We investigated possible effects on cognitive function in an urban population with chronic, low-level exposure to H2S.

METHODS

Participants were 1637 adults, aged 18-65 years from Rotorua city, New Zealand, exposed to ambient H2S from geothermal sources. Exposures at homes and workplaces were estimated from data collected by summer and winter H2S monitoring networks across Rotorua in 2010/11. Metrics for H2S exposure at the time of participation and for exposure over the last 30 years were calculated. H2S exposure was modeled both as continuous variables and as quartiles of exposure covering the range of 0-64 ppb (0-88 μg/m(3)). Outcomes were neuropsychological tests measuring visual and verbal episodic memory, attention, fine motor skills, psychomotor speed and mood. Associations between cognition and measures of H2S exposure were investigated with multiple regression, while covarying demographics and factors known to be associated with cognitive performance.

RESULTS

The consistent finding was of no association between H2S exposure and cognition. Quartiles of H2S exposure had a small association with simple reaction time: higher exposures were associated with faster response times. Similarly, for digit symbol, higher H2S exposures tended to be marginally associated with better performance.

CONCLUSION

The results provide evidence that chronic H2S exposure, at the ambient levels found in and around Rotorua, is not associated with impairment of cognitive function.

Monitoring cognitive functioning: psychometric properties of the brief test of adult cognition by telephone

Assessment of cognitive functioning is an important component of telephone surveys of health. Previous cognitive telephone batteries have been limited in scope with a primary focus on dementia screening. The Brief Test of Adult Cognition by Telephone (BTACT) assesses multiple dimensions central for effective functioning across adulthood: episodic memory, working memory, reasoning, verbal fluency, and executive function. The BTACT is the first instrument that includes measures of processing speed, reaction time, and task-switching/inhibitory control for use over the telephone. We administered the battery to a national sample (N = 4,268), age 32 to 84 years, from the study of Midlife in the United States (MIDUS) and examined age, education, and sex differences; reliability; and factor structure. We found good evidence for construct validity with a subsample tested in person. Implications of the findings are considered for efficient neuropsychological assessment and monitoring changes in cognitive aging, for clinical and research applications by telephone or in person.

Application of audio computer-assisted self-interviews to collect self-reported health data: an overview

For assessment of sensitive health behaviors (e.g., sexual behavior, violent behaviors, substance use), research is typically limited to an examination of self-reports of past behavior. Audio computer-assisted self-interviews (ACASI) may enhance the validity of self-report data in research and clinical settings by reducing measurement bias. This paper provides an introduction to ACASI for collection of self-reported health data. The potential benefits and cost-effectiveness of ACASI use in research and clinical settings are reviewed. We then review the theoretical underpinnings that may underlie differential reporting of health behaviors between assessment modalities. Next, we highlight studies that have investigated differences in self-reported health behaviors between assessment modalities. Lastly, we summarize potential applications of ACASI assessments within clinical settings.

Modeling of cognitive impairment by disease duration in multiple sclerosis: a cross-sectional study

BACKGROUND/AIMS

Large-scale population studies measuring rates and dynamics of cognitive decline in multiple sclerosis (MS) are lacking. In the current cross-sectional study we evaluated the patterns of cognitive impairment in MS patients with disease duration of up to 30 years.

METHODS

1,500 patients with MS were assessed by a computerized cognitive battery measuring verbal and non-verbal memory, executive function, visual spatial perception, verbal function, attention, information processing speed and motor skills. Cognitive impairment was defined as below one standard deviation (SD) and severe cognitive impairment as below 2SD for age and education matched healthy population norms.

RESULTS

Cognitive performance in our cohort was poorer than healthy population norms. The most frequently impaired domains were information processing speed and executive function. MS patients with secondary-progressive disease course performed poorly compared with clinically isolated syndrome, relapsing-remitting and primary progressive MS patients. By the fifth year from disease onset, 20.9% of patients performed below the 1SD cutoff for impairment, p=0.005, and 6.0% performed below the 2SD cutoff for severe cognitive impairment, p=0.002. By 10 years from onset 29.3% and 9.0% of patients performed below the 1SD and 2SD cutoffs, respectively, p=0.0001. Regression modeling suggested that cognitive impairment may precede MS onset by 1.2 years.

CONCLUSIONS

The rates of cognitive impairment in this large sample of MS patients were lower than previously reported and severe cognitive impairment was evident only in a relatively small group of patients. Cognitive impairment differed significantly from expected normal distribution only at five years from onset, suggesting the existence of a therapeutic window during which patients may benefit from interventions to maintain cognitive health.

Neurobehavioral function and low-level exposure to brominated flame retardants in adolescents: a cross-sectional study

BACKGROUND

Animal and in vitro studies demonstrated a neurotoxic potential of brominated flame retardants, a group of chemicals used in many household and commercial products to prevent fire. Although the first reports of detrimental neurobehavioral effects in rodents appeared more than ten years ago, human data are sparse.

METHODS

As a part of a biomonitoring program for environmental health surveillance in Flanders, Belgium, we assessed the neurobehavioral function with the Neurobehavioral Evaluation System (NES-3), and collected blood samples in a group of high school students. Cross-sectional data on 515 adolescents (13.6-17 years of age) was available for the analysis. Multiple regression models accounting for potential confounders were used to investigate the associations between biomarkers of internal exposure to brominated flame retardants [serum levels of polybrominated diphenyl ether (PBDE) congeners 47, 99, 100, 153, 209, hexabromocyclododecane (HBCD), and tetrabromobisphenol A (TBBPA)] and cognitive performance. In addition, we investigated the association between brominated flame retardants and serum levels of FT3, FT4, and TSH.

RESULTS

A two-fold increase of the sum of serum PBDE's was associated with a decrease of the number of taps with the preferred-hand in the Finger Tapping test by 5.31 (95% CI: 0.56 to 10.05, p = 0.029). The effects of the individual PBDE congeners on the motor speed were consistent. Serum levels above the level of quantification were associated with an average decrease of FT3 level by 0.18 pg/mL (95% CI: 0.03 to 0.34, p = 0.020) for PBDE-99 and by 0.15 pg/mL (95% CI: 0.004 to 0.29, p = 0.045) for PBDE-100, compared with concentrations below the level of quantification. PBDE-47 level above the level of quantification was associated with an average increase of TSH levels by 10.1% (95% CI: 0.8% to 20.2%, p = 0.033), compared with concentrations below the level of quantification. We did not observe effects of PBDE's on neurobehavioral domains other than the motor function. HBCD and TBBPA did not show consistent associations with performance in the neurobehavioral tests.

CONCLUSIONS

This study is one of few studies and so far the largest one investigating the neurobehavioral effects of brominated flame retardants in humans. Consistently with experimental animal data, PBDE exposure was associated with changes in the motor function and the serum levels of the thyroid hormones.

Neurobehavioral function and organophosphate insecticide use among pesticide applicators in the Agricultural Health Study

Although persistent decrements in cognitive function have been observed among persons who have recovered from clinically overt organophosphate (OP) pesticide poisoning, little is known about the cognitive effects of chronic OP exposures that do not result in acute poisoning. To examine associations between long-term pesticide use and neurobehavioral (NB) function, NB tests were administered to licensed pesticide applicators enrolled in the Agricultural Health Study (AHS) in Iowa and North Carolina. Between 2006 and 2008, 701 male participants completed nine NB tests to assess memory, motor speed and coordination, sustained attention, verbal learning and visual scanning and processing. Data on ever-use and lifetime days of use of 16 OP pesticides were obtained from AHS interviews conducted before testing between 1993 and 2007 and during the NB visit. The mean age of participants was 61 years (SD=12). Associations between pesticide use and NB test performance were estimated with linear regression controlling for age and outcome-specific covariates. NB test performance was associated with lifetime days of use of some pesticides. Ethoprop was significantly associated with reduced performance on a test of motor speed and visual scanning. Malathion was significantly associated with poor performance on a test of visual scanning and processing. Conversely, we observed significantly better test performance for five OP pesticides. Specifically, chlorpyrifos, coumaphos, parathion, phorate, and tetrachlorvinphos were associated with better verbal learning and memory; coumaphos was associated with better performance on a test of motor speed and visual scanning; and parathion was associated with better performance on a test of sustained attention. Several associations varied by state. Overall, we found no consistent evidence of an association between OP pesticide use and adverse NB test performance among this older sample of pesticide applicators. Potential reasons for these mostly null results include a true absence of effect as well as possible selective participation by healthier applicators.

The effects of binge drinking on college students' next-day academic test-taking performance and mood state

AIM

To assess the effects of binge drinking on students' next-day academic test-taking performance.

DESIGN

A placebo-controlled cross-over design with randomly assigned order of conditions. Participants were randomized to either alcoholic beverage [mean = 0.12 g% breath alcohol concentration (BrAC)] or placebo on the first night and then received the other beverage a week later. The next day, participants were assessed on test-taking, neurocognitive performance and mood state.

PARTICIPANTS

A total of 196 college students (>or=21 years) recruited from greater Boston.

SETTING

The trial was conducted at the General Clinical Research Center at the Boston Medical Center.

MEASUREMENTS

The Graduate Record Examinations(c) (GREs) and a quiz on a lecture presented the previous day measured test-taking performance; the Neurobehavioral Evaluation System (NES3) and the Psychomotor Vigilance Test (PVT) measured neurocognitive performance; and the Profile of Mood States (POMS) measured mood.

FINDINGS

Test-taking performance was not affected on the morning after alcohol administration, but mood state and attention/reaction-time were affected.

CONCLUSION

Drinking to a level of 0.12 g% BrAC does not affect next-day test-taking performance, but does affect some neurocognitive measures and mood state.

Intoxication with bourbon versus vodka: effects on hangover, sleep, and next-day neurocognitive performance in young adults

BACKGROUND

This study assessed the effects of heavy drinking with high or low congener beverages on next-day neurocognitive performance, and the extent to which these effects were mediated by alcohol-related sleep disturbance or alcoholic beverage congeners, and correlated with the intensity of hangover.

METHODS

Healthy heavy drinkers age 21 to 33 (n = 95) participated in 2 drinking nights after an acclimatization night. They drank to a mean of 0.11 g% breath alcohol concentration on vodka or bourbon one night with matched placebo the other night, randomized for type and order. Polysomnography recordings were made overnight; self-report and neurocognitive measures were assessed the next morning.

RESULTS

After alcohol, people had more hangover and more decrements in tests requiring both sustained attention and speed. Hangover correlated with poorer performance on these measures. Alcohol decreased sleep efficiency and rapid eye movement sleep, and increased wake time and next-day sleepiness. Alcohol effects on sleep correlated with hangover but did not mediate the effects on performance. No effect of beverage congeners was found except on hangover severity, with people feeling worse after bourbon. Virtually no sex differences appeared.

CONCLUSIONS

As drinking to this level affects complex cognitive abilities, safety could be affected, with implications for driving and for safety-sensitive occupations. Congener content affects only how people feel the next day so does not increase risk. The sleep disrupting effects of alcohol did not account for the impaired performance so other mechanisms of effect need to be sought. As hangover symptoms correlate with impaired performance, these might be contributing to the impairment.

Computer-assisted self-interviews: a cost effectiveness analysis

Computer-assisted self-interview (CASI) questionnaires are being used with increased frequency to deliver surveys that previously were administered via self-administeredpaper-and-pencil questionnaires (SAQs). Although CASI may offer a number of advantages, an important consideration for researchers is the assessment modality's immediate and long-term costs. To facilitate researchers' choice between CASI and SAQ, this article provides theoretical cost models with specific parameters for comparing the costs for each assessment type. Utilizing these cost models, this study compared the cost effectiveness in a health behavior study in which both CASI (n = 100) and SAQ (n = 100) questionnaires were administered. Given the high initial costs, CASI was found to be less cost effective than SAQ for a single study. However, for studies with large sample sizes or when CASI software is to be used for multiple studies, CASI would be more cost effective and should be the assessment mode of choice.

Chemobrain: a translational challenge for neurotoxicology

Neurotoxicity is a frequent accompaniment of cancer chemotherapy, and held by many oncologists to be the major dose-limiting side effect. It appears in many forms, but attracted attention during the past decade primarily because of complaints by patients of impaired cognitive function they have labeled as "chemobrain". Neuropsychological testing confirmed the validity of these complaints and has generated a substantial literature examining different aspects of cognitive impairment in various clinical populations undergoing a variety of treatments. Cognitive impairment is far from the only manifestation of neurotoxicity induced by chemotherapy, however. It alters sensory function and motor function as well. A critical need for patients is a suite of methods that will enable clinicians to trace the onset and progression of neurotoxicity so as to guide and balance decisions about the course of chemotherapy. This commentary describes some of the potential methods and encourages neurotoxicologists to enlist their unique skills in the service of these needs.

Prolonged response times characterize cognitive performance in multiple sclerosis

Cognitive impairment is amongst the main symptoms affecting multiple sclerosis (MS) and should be comprehensively and accurately assessed. To study the added value of a computerized neuropsychological battery enabling the measurement of response times in the cognitive domains, 58 randomly selected MS patients and 71 age-, gender- and education-matched healthy subjects were evaluated. Construct and discriminant validity were assessed for the standard Neuropsychological Screening Battery for Multiple Sclerosis (NSBMS) and the Mindstreams Computerized Cognitive Battery (MCCB). The MCCB demonstrated good construct validity in comparison with the NSBMS in memory (P < 0.001), executive function (P < 0.001), attention (P < 0.05) and information processing (P < 0.05) domains. In addition, it showed high discriminant validity most prominently for executive function, attention and motor skills (P < 0.001). Response times measured by the computerized battery were longer in all cognitive domains and varied with cognitive load, demonstrating that response time deficits in MS are associated with particular task demands. We conclude that in MS prolonged response times on a range of cognitive tasks signify abnormal conduction within demyelinative tracts.

Repeated split sample validation to assess logistic regression and recursive partitioning: an application to the prediction of cognitive impairment

Screening strategies play an important part in the identification and diagnosis of illness. Testing of such strategies in a clinical trial can have important implications for the treatment of such illnesses. Before the clinical trial, however, it is important to develop a practical screening/classification procedure that accurately predicts the presence of the illness in question. Recent published studies have shown a growing preference for classification tree/recursive partitioning procedures.This paper compares the application of logistic regression and recursive partitioning to a neuropsychological data set of 252 patients recruited from four Veterans Affairs Medical Centers. Logistic regression and recursive partitioning was used to predict cognitive impairment in 12 randomly selected exploratory/validation samples. We assessed the effect of sampling on variable selection and predictive accuracy.Predictive accuracy of the logistic regression and recursive partitioning procedures was comparable across the exploratory data samples but varied across the validation samples. Based on shrinkage, both classification procedures performed equally well for the prediction of cognitive impairment across the twelve samples. While logistic regression provided an estimated probability of outcome for each patient, it required several mathematical calculations to do so. However, logistic regression selected one or two less predictors than recursive partitioning with comparable predictive accuracy. Recursive partitioning, on the other hand, readily identified patient characteristics and variable interactions, was easy to interpret clinically and required no mathematical calculations. There was a high degree of overlap of the predictor variables between the two procedures.In the context of neuropsychological screening, logistic regression and recursive partitioning performed equally well and were quite stable in the selection of predictors for the identification of patients with cognitive impairment, although recursive partitioning may be easier to use in a clinical setting because it is based on a simple decision tree.

Imaging is superior to cognitive testing for early diagnosis of Alzheimer’s disease

Alzheimer's disease (AD) starts at a molecular level possibly decades earlier than could be detected by neuropsychological tests (NPTs). Neuropathological and neuroimaging data suggest that amyloid accumulation precedes the clinical onset of AD. Disease-modifying agents would have to be used early to alter the course of AD. Therefore, preclinical diagnosis is necessary. Structural and functional neuroimaging are superior for detection of the earliest stages of AD. Magnetic resonance imaging (MRI) and positron emission tomography (PET) techniques, including amyloid visualization, will have therapeutic importance for prevention as well as intervention as further refinements of current imaging techniques and biochemical markers occur. Neuropsychological tests measure the effect of pathology for an individual based upon norms obtained from an artificial population-often white and relatively highly educated. Unless serial NPTs are performed, the individual is compared to a population to which they may not conform. Neuroimaging can provide objective measures of preclinical disease state and, when measured serially, rate of change. Such information can be used in prevention trials.

Validity of a novel computerized cognitive battery for mild cognitive impairment

BACKGROUND

The NeuroTrax Mindstreams computerized cognitive assessment system was designed for widespread clinical and research use in detecting mild cognitive impairment (MCI). However, the capability of Mindstreams tests to discriminate elderly with MCI from those who are cognitively healthy has yet to be evaluated. Moreover, the comparability between these tests and traditional neuropsychological tests in detecting MCI has not been examined.

METHODS

A 2-center study was designed to assess discriminant validity of tests in the Mindstreams Mild Impairment Battery. Participants were 30 individuals diagnosed with MCI, 29 with mild Alzheimer's disease (AD), and 39 healthy elderly. Testing was with the Mindstreams battery and traditional neuropsychological tests. Receiver operating characteristic (ROC) analysis was used to examine the ability of Mindstreams and traditional measures to discriminate those with MCI from cognitively healthy elderly. Between-group comparisons were made (Mann-Whitney U test) between MCI and healthy elderly and between MCI and mild AD groups.

RESULTS

Mindstreams outcome parameters across multiple cognitive domains significantly discriminated among MCI and healthy elderly with considerable effect sizes (p < 0.05). Measures of memory, executive function, visual spatial skills, and verbal fluency discriminated best, and discriminability was at least comparable to that of traditional neuropsychological tests in these domains.

CONCLUSIONS

Mindstreams tests are effective in detecting MCI, providing a comprehensive profile of cognitive function. Further, the enhanced precision and ease of use of these computerized tests make the NeuroTrax system a valuable clinical tool in the identification of elderly at high risk for dementia.

Further standardization of some NES3 tests

NES3 is a computer-based neurobehavioral testing system designed for use in investigating potential cognitive impairment. Data from NES3 tests employed in a study of epilepsy self-management were analyzed to estimate test-retest reliability for NES3 tests on a large sample and to estimate the effect of some common covariates of test performance. A total of 319 participants in an epilepsy self-management study were examined on three occasions (baseline, 3-month follow-up, and 6-month follow-up) with a set of psychological questionnaires and seven neuropsychological tests from NES3. Test-retest correlations were calculated between measures obtained at baseline and at 3 months. Principal components analysis was performed on the baseline data. The potential effects of covariates (age, education, reading test scores, depression status, and examiner) were investigated in regression models. Three-month test-retest correlations were excellent for Adult Reading Test (ART) (r=0.95), strong for Digit-Symbol (r=0.82), Sequence B (r=0.79), and Sequence A (r=0.76); and modest (r's between 0.56 and 0.67) for Digit Span Forward and Backward, Visual Span Forward and Backward, and Pattern Memory. Alternate-forms correlations were strong for HVLT (r's between 0.71 and 0.82). Principal components analysis yielded four interpretable components. Age and reading score were significant covariates of virtually all of the test summary measures, while education, gender, race, and depression were not generally significant covariates. Changes to the method of calculation of some summary measures, changes to the initial instructions to the subjects, and addition of correctional feedback to subjects during the tests appeared to improve the reliability of some NES3 tests. Implementation of the HVLT and ART in computer-assisted format added breadth of coverage to the battery. NES3 tests may provide reliable, efficient data for use in epidemiologic studies of potential cognitive effects of occupational and environmental exposures.

Continuing challenges for computer-based neuropsychological tests

A number of issues critical to the development of computer-based neuropsychological testing systems that remain continuing challenges to their widespread use in occupational and environmental health are reviewed. Several computer-based neuropsychological testing systems have been developed over the last 20 years, and they have contributed substantially to the study of neurologic effects of a number of environmental exposures. However, many are no longer supported and do not run on contemporary personal computer operating systems. Issues that are continuing challenges for development of computer-based neuropsychological tests in environmental and occupational health are discussed: (1) some current technological trends that generally make test development more difficult; (2) lack of availability of usable speech recognition of the type required for computer-based testing systems; (3) implementing computer-based procedures and tasks that are improvements over, not just adaptations of, their manually-administered predecessors; (4) implementing tests of a wider range of memory functions than the limited range now available; (5) paying more attention to motivational influences that affect the reliability and validity of computer-based measurements; and (6) increasing the usability of and audience for computer-based systems. Partial solutions to some of these challenges are offered. The challenges posed by current technological trends are substantial and generally beyond the control of testing system developers. Widespread acceptance of the "tablet PC" and implementation of accurate small vocabulary, discrete, speaker-independent speech recognition would enable revolutionary improvements to computer-based testing systems, particularly for testing memory functions not covered in existing systems. Dynamic, adaptive procedures, particularly ones based on item-response theory (IRT) and computerized-adaptive testing (CAT) methods, will be implemented in new tests that will be more efficient, reliable, and valid than existing test procedures. These additional developments, along with implementation of innovative reporting formats, are necessary for more widespread acceptance of the testing systems.