CARE4Kids Study: Endophenotypes of Persistent Post-Concussive Symptoms in Adolescents: Study Rationale and Protocol.

Treatment of youth concussion during the acute phase continues to evolve, and this has led to the emergence of guidelines to direct care. While symptoms after concussion typically resolve in 14-28 days, a portion (∼20%) of adolescents endorse persistent post-concussive symptoms (PPCS) beyond normal resolution. This report outlines a study implemented in response to the National Institute of Neurological Diseases and Stroke call for the development and initial clinical validation of objective biological measures to predict risk of PPCS in adolescents. We describe our plans for recruitment of a Development cohort of 11- to 17-year-old youth with concussion, and collection of autonomic, neurocognitive, biofluid, and imaging biomarkers. The most promising of these measures will then be validated in a separate Validation cohort of youth with concussion, and a final, clinically useful algorithm will be developed and disseminated. Upon completion of this study, we will have generated a battery of measures predictive of high risk for PPCS, which will allow for identification and testing of interventions to prevent PPCS in the most high-risk youth.

Association Between Early Return to School Following Acute Concussion and Symptom Burden at 2 Weeks Postinjury.

Importance: Determining how the timing of return to school is related to later symptom burden is important for early postinjury management recommendations. Objective: To examine the typical time to return to school after a concussion and evaluate whether an earlier return to school is associated with symptom burden 14 days postinjury. Design, Setting, and Participants: Planned secondary analysis of a prospective, multicenter observational cohort study from August 2013 to September 2014. Participants aged 5 to 18 years with an acute (<48 hours) concussion were recruited from 9 Canadian pediatric emergency departments in the Pediatric Emergency Research Canada Network. Exposure: The independent variable was the number of days of school missed. Missing fewer than 3 days after concussion was defined as an early return to school. Main Outcomes and Measures: The primary outcome was symptom burden at 14 days, measured with the Post-Concussion Symptom Inventory (PCSI). Symptom burden was defined as symptoms status at 14 days minus preinjury symptoms. Propensity score analyses applying inverse probability of treatment weighting were performed to estimate the relationship between the timing of return to school and symptom burden. Results: This cohort study examined data for 1630 children (mean age [SD] 11.8 [3.4]; 624 [38%] female). Of these children, 875 (53.7%) were classified as having an early return to school. The mean (SD) number of days missed increased across age groups (5-7 years, 2.61 [5.2]; 8-12 years, 3.26 [4.9]; 13-18 years, 4.71 [6.1]). An early return to school was associated with a lower symptom burden 14 days postinjury in the 8 to 12-year and 13 to 18-year age groups, but not in the 5 to 7-year age group. The association between early return and lower symptom burden was stronger in individuals with a higher symptom burden at the time of injury, except those aged 5 to 7 years. Conclusions and Relevance: In this cohort study of youth aged 5 to 18 years, these results supported the growing belief that prolonged absences from school and other life activities after a concussion may be detrimental to recovery. An early return to school may be associated with a lower symptom burden and, ultimately, faster recovery.

Effect of Cognitive and Physical Rest on Persistent Postconcussive Symptoms following a Pediatric Head Injury.

OBJECTIVE: To evaluate the effect of cognitive and physical rest on persistent postconcussive symptoms in a pediatric population. STUDY DESIGN: A prospective cohort study of 5- to 18-year-olds diagnosed with an acute concussion in a tertiary care pediatric emergency department was conducted from December 2016 to May 2019. Participants (n = 119) were followed over 1 month to track days off from school and sports and the development of persistent postconcussive symptoms (residual concussion symptoms beyond 1 month). Participants were dichotomized into minimal (≤2) and moderate (>2) rest, based on days off from school and sports after a concussion. Univariate and multivariable logistic regression analyses were completed to examine associations with persistent postconcussive symptoms. RESULTS: Of the participants in our study, 24% had persistent postconcussive symptoms. Adolescent age, history of prolonged concussion recovery, and headache at presentation were associated with higher odds of persistent postconcussive symptoms in univariate analyses. In a multivariable logistic regression model, only adolescent age was associated with increased odds of persistent postconcussive symptoms. Compared with the minimal cognitive rest group, moderate cognitive rest did not decrease the odds of persistent postconcussive symptoms (aOR, 1.15; 95% CI, 0.44-2.99). Compared with the minimal physical rest group, moderate physical rest also did not decrease the odds of persistent postconcussive symptoms (aOR, 3.17; 95% CI, 0.35-28.78). CONCLUSIONS: Emerging evidence supports early return to light activity for recovery of acute pediatric concussion. Our study adds to this management approach as we did not find that rest from school and sports resulted in a decreased odds of persistent postconcussive symptoms.

Measuring Dynamic Symptom Response in Concussion: Children's Exertional Effects Rating Scale.

OBJECTIVE: To introduce and evaluate a measure of momentary symptom response to cognitive activity, a core feature of concussion. SETTING: Concussion clinic at a large regional children's hospital. PARTICIPANTS: Individuals aged 5 to 18 years, comprising 3 clinical groups: uninjured (n = 590), recently concussed but clinically recovered (n = 160), and recently concussed but not yet recovered (n = 570). DESIGN: Participants completed pretest symptom ratings, underwent neurocognitive assessment and completion of questionnaires, and then completed posttest ratings. An exertional effects index was computed by subtracting pretest from posttest ratings. MAIN MEASURES: Children's Exertional Effects Rating Scale, which includes 4 symptoms (Headache, Fatigue, Concentration Problems, and Irritability) rated pre- and postactivity. RESULTS: Children's Exertional Effects Rating Scale was found to have adequate reliability and validity. There were negligible differences in ratings (pretest and exertional effects) between the Uninjured and Recovered groups, while individuals who were Not Recovered rated higher levels of pretest and exertional effects. Base rates showed that an exertional effects index of 4 or more points is rare in individuals who do not have a current concussion. CONCLUSION: Children's Exertional Effects Rating Scale is a psychometrically sound scale for evaluating momentary symptom increase in response to cognitive activity. Clinicians can use this scale as part of a multimodal battery for concussion assessment and treatment.

Applying an Evidence-Based Assessment Model to Identify Students at Risk for Perceived Academic Problems following Concussion.

OBJECTIVES: The aim of this study was to demonstrate the utility of an evidence-based assessment (EBA) model to establish a multimodal set of tools for identifying students at risk for perceived post-injury academic problems. METHODS: Participants included 142 students diagnosed with concussion (age: M=14.95; SD=1.80; 59% male), evaluated within 4 weeks of injury (median=16 days). Demographics, pre-injury history, self- and parent-report measures assessing symptom severity and executive functions, and cognitive test performance were examined as predictors of self-reported post-injury academic problems. RESULTS: Latent class analysis categorized participants into "high" (44%) and "low" (56%) levels of self-reported academic problems. Receiver operating characteristic analyses revealed significant discriminative validity for self- and parent-reported symptom severity and executive dysfunction and self-reported exertional response for identifying students reporting low versus high academic problems. Parent-reported symptom ratings [area under the receiver operating characteristic curve (AUC)=.79] and executive dysfunction (AUC=.74), and self-reported ratings of executive dysfunction (AUC=.84), symptoms (AUC=.80), and exertional response (AUC=.70) each classified students significantly better than chance (ps<.001). Hierarchical logistic regression indicated that, of the above, self-reported symptoms and executive dysfunction accounted for the most variance in the prediction of self-reported academic problems. CONCLUSIONS: Post-concussion symptom severity and executive dysfunction significantly predict perceived post-injury academic problems. EBA modeling identified the strongest set of predictors of academic challenges, offering an important perspective in the management of concussion by applying traditional strengths of neuropsychological assessment to clinical decision making. (JINS, 2016, 22, 1038-1049).

Subconcussive Head Impact Exposure and White Matter Tract Changes over a Single Season of Youth Football.

Purpose To examine the effects of subconcussive impacts resulting from a single season of youth (age range, 8-13 years) football on changes in specific white matter (WM) tracts as detected with diffusion-tensor imaging in the absence of clinically diagnosed concussions. Materials and Methods Head impact data were recorded by using the Head Impact Telemetry system and quantified as the combined-probability risk-weighted cumulative exposure (RWECP). Twenty-five male participants were evaluated for seasonal fractional anisotropy (FA) changes in specific WM tracts: the inferior fronto-occipital fasciculus (IFOF), inferior longitudinal fasciculus, and superior longitudinal fasciculus (SLF). Fiber tracts were segmented into a central core and two fiber terminals. The relationship between seasonal FA change in the whole fiber, central core, and the fiber terminals with RWECP was also investigated. Linear regression analysis was conducted to determine the association between RWECP and change in fiber tract FA during the season. Results There were statistically significant linear relationships between RWEcp and decreased FA in the whole (R2 = 0.433; P = .003), core (R2 = 0.3649; P = .007), and terminals (R2 = 0.5666; P < .001) of left IFOF. A trend toward statistical significance (P = .08) in right SLF was observed. A statistically significant correlation between decrease in FA of the right SLF terminal and RWECP was also observed (R2 = 0.2893; P = .028). Conclusion This study found a statistically significant relationship between head impact exposure and change of FA fractional anisotropy value of whole, core, and terminals of left IFOF and right SLF's terminals where WM and gray matter intersect, in the absence of a clinically diagnosed concussion. © RSNA, 2016.

Additional Post-Concussion Impact Exposure May Affect Recovery in Adolescent Athletes.

Repeat concussion has been associated with risk for prolonged and pronounced clinical recovery in athletes. In this study of adolescent athletes, we examined whether an additional head impact within 24 h of a sports-related concussion (SRC) is associated with higher symptom burden and prolonged clinical recovery compared with a single-injury group. Forty-two student-athletes (52% male, mean age = 14.9 years) diagnosed with an SRC in a concussion clinic were selected for this study: (1) 21 athletes who sustained an additional significant head impact within 24 h of the initial injury (additional-impact group); (2) 21 single-injury athletes, age and gender matched, who sustained only one discrete concussive blow to the head (single-injury group). Groups did not differ on initial injury characteristics or pre-injury risk factors. The effect of injury status (single- vs. additional-impact) was examined on athlete- and parent-reported symptom burden (at first clinic visit) and length of recovery (LOR). Higher symptom burden was reported by the athletes and parents in the additional-impact group at the time of first visit. The additional-impact group also had a significantly longer LOR compared with the single-injury group. These findings provide preliminary, hypothesis-generating evidence for the importance of immediate removal from play following an SRC to protect athletes from re-injury, which may worsen symptoms and prolong recovery. The retrospective study design from a specialized clinical sample points to the need for future prospective studies of the relationship between single- and additional-impact injuries on symptom burden and LOR.

Subconcussive impacts and imaging findings over a season of contact sports.

The effect of repeated subconcussive head impacts in youth and high school sports on the developing brain is poorly understood. Emerging neuroimaging data correlated with biomechanical exposure metrics are beginning to demonstrate relationships across a variety of modalities. The long-term consequences of these changes are unknown. A review of the currently available literature on the effect of subconcussive head impacts on youth and high school-age male football players provides compelling evidence for more focused studies of these effects in these vulnerable populations.

Academic effects of concussion in children and adolescents.

OBJECTIVE: The aim of this work is to study the nature and extent of the adverse academic effects faced by students recovering from concussion. METHOD: A sample of 349 students ages 5 to 18 who sustained a concussion and their parents reported academic concerns and problems (eg, symptoms interfering, diminished academic skills) on a structured school questionnaire within 4 weeks of injury. Postconcussion symptoms were measured as a marker of injury severity. Results were examined based on recovery status (recovered or actively symptomatic) and level of schooling (elementary, middle, and high school). RESULTS: Actively symptomatic students and their parents reported higher levels of concern for the impact of concussion on school performance (P < .05) and more school-related problems (P < .001) than recovered peers and their parents. High school students who had not yet recovered reported significantly more adverse academic effects than their younger counterparts (P < .05). Greater severity of postconcussion symptoms was associated with more school-related problems and worse academic effects, regardless of time since injury (P < .001). CONCLUSIONS: This study provides initial evidence for a concussion's impact on academic learning and performance, with more adverse effects reported by students who had not yet recovered from the injury. School-based management with targeted recommendations informed by postinjury symptoms may mitigate adverse academic effects, reduce parent and student concerns for the impact of the injury on learning and scholastic performance, and lower the risk of prolonged recovery for students with active postconcussion symptoms.

The Relation Between Testing Environment and Baseline Performance in Child and Adolescent Concussion Assessment.

BACKGROUND: Previous research has demonstrated differences in cognitive performance when baseline concussion assessment is performed in a group versus an individual setting. Accurate baseline assessment is imperative when such data are used to make clinical decisions regarding cognitive and symptom recovery after concussion. HYPOTHESIS: The use of similar standardized test administration procedures and test conditions across group and individual settings results in no differences in cognitive performance or symptom reporting. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: A total of 939 participants (aged 5-18 years), including 313 tested individually and 626 tested in a group setting, matched on age, sex, and attention-deficit/hyperactivity disorder status, were administered concussion baseline assessment using the desktop version of the Immediate Post-Concussion Assessment and Cognitive Testing and a new pediatric measure, the Multimodal Assessment of Cognition & Symptoms for Children. Cognitive performance, symptom reports, and rates of invalid performance were compared between settings. RESULTS: No significant differences were found between individual and group testing settings for the age-based Learning and Memory Accuracy composite and Response Speed composite standard scores on the Multimodal Assessment of Cognition & Symptoms for Children. Accounting for age and sex, adolescents' performance on the Immediate Post-Concussion Assessment and Cognitive Testing revealed no differences between settings on the 4 composite raw scores (Verbal Memory, Visual Memory, Visual Motor Speed, and Reaction Time). Furthermore, symptom reporting was similar between settings on both measures. Rates of invalid performance did not differ between the 2 administration groups for either age group. There was an interaction effect for invalid performance between attention-deficit/hyperactivity disorder and setting in younger children (aged 5-12 years), with higher rates of invalid performance for children in the group setting with attention-deficit/hyperactivity disorder compared with those without, although there were no differences in the individual setting. CONCLUSION: In this sample, children given a baseline assessment in a group setting performed no differently than children tested individually when standardized administration procedures were used by trained test administrators. Previous evidence suggesting differences between settings may be attributable to the variability in test administration and supervision rather than the environment itself. The importance of standardized procedures and proper supervision during baseline concussion assessment is supported by these findings.

Psychometric characteristics of the postconcussion symptom inventory in children and adolescents.

Psychometric characteristics of the Postconcussion Symptom Inventory (PCSI) were examined in both concussed (n = 633) and uninjured (n = 1,273) 5 to 18 year olds. Parent- and self-report forms were created with developmentally appropriate wording and content. Factor analyses identified physical, cognitive, emotional, and sleep factors; that did not load strongly or discriminate between groups were eliminated. Internal consistency was strong for the total scales (α = 0.8-0.9). Test-retest reliability for the self-report forms was moderate to strong (intraclass coeffecients, ICCs = 0.65-0.89). Parent and self-report concordance was moderate (r = .44-.65), underscoring the importance of both perspectives. Convergent validity with another symptom measure was good (r = .8). Classification analyses indicated greater discriminability from parent report, but caveats to this are presented. With strong psychometric characteristics, the four versions of the PCSI capture important postconcussion symptoms and can be utilized to track recovery from pediatric concussion and guide treatment recommendations.

Assessment of processing speed in children with mild TBI: a "first look" at the validity of pediatric ImPACT.

UNLABELLED: Deficit in the speed of cognitive processing is a commonly identified neuropsychological change in children recovering from a mild TBI. However, there are few validated child assessment instruments that allow for serial assessment over the course of recovery in this population. Pediatric ImPACT is a novel measure that purports to assess cognitive speed, learning, and efficiency in this population. The current study sought to validate the use of this new measure by comparing it to traditional paper and pencil measures of processing speed. METHOD: One hundred and sixty-four children (71% male) age 5-12 with mild TBI evaluated in an outpatient concussion clinic were administered Pediatric ImPACT and other neuropsychological test measures as part of a flexible test battery. RESULTS: Performance on the Response Speed Composite of Pediatric ImPACT was more strongly associated with other measures of cognitive processing speed, than with measures of immediate/working memory and learning/memory in this sample of injured children. CONCLUSIONS: There is preliminary support for convergent and discriminant validity of Pediatric ImPACT as a measure for use in post-concussion evaluations of processing speed in children.

Computerized assessment of cognitive late effects among adolescent brain tumor survivors.

Advantages of computerized assessment of neuropsychological functions include improved standardization and increased reliability of response time variables. Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) is a computerized battery developed for monitoring recovery following mild brain injuries that assesses attention, memory and processing speed. Despite evidence that core areas of deficit among cancer survivors are those assessed by ImPACT, it has not previously been used with this population. Twenty four childhood brain tumor (BT) survivors treated with conformal radiation therapy (mean age = 15.7 ± 1.6; mean age at irradiation = 9.8 ± 2.5), twenty solid tumor (ST) survivors treated without CNS-directed therapy (mean age = 16.2 ± 1.8) and twenty healthy siblings (mean age = 15.1 ± 1.6 years) were administered an age modified version of ImPACT. Additional computerized measures of working memory and recognition memory were administered. Univariate ANOVAs revealed group differences (p < 0.05) on measures of recognition memory, spatial working memory, processing speed and reaction time, with BT survivors performing significantly worse than ST survivors and siblings. Pearson correlation coefficients revealed significant associations between ImPACT memory tasks and computerized forced choice recognition tasks (rs = 0.30-0.33, p < 0.05). Multiple surgical resections, hydrocephalus and CSF shunt placement most consistently predicted worse ImPACT performance using linear mixed models (p < 0.05). The ImPACT test battery demonstrated sensitivity to cognitive late effects experienced by some BT survivors with clinical predictors of performance consistent with the pediatric oncology literature. Correlations with measures of similar constructs provide evidence for convergent validity. Findings offer initial support for the utility of ImPACT for monitoring of cognitive late effects.

School and the concussed youth: recommendations for concussion education and management.

School learning and performance is arguably the critical centerpiece of child and adolescent development, and there can be significant temporary upset in cognitive processing after a mild traumatic brain injury, also called a concussion. This injury results in a cascade of neurochemical abnormalities, and, in the wake of this dysfunction, both physical and cognitive activities become sources of additional neurometabolic demand on the brain and may cause symptoms to reemerge or worsen. This article provides a foundation for postinjury management of cognitive activity, particularly in the school setting, including design and implementation of schoolwide concussion education and management programs.

Executive function modifies the relationship between occupational lead exposure and complex figure test performance.

OBJECTIVES: To determine if chronic lead exposure is associated with non-verbal memory performance and if this association is affected by organisation strategies, a component of executive functions. METHODS: We administered the Rey-Osterrieth Complex Figure (ROCF) test, both copy (ROCF-C) and 30-min delayed recall (ROCF-DR), to 358 current lead smelter workers with a mean (SD) age of 41 (9.1) years, education of 11 (2.7) years, and working lifetime-weighted average blood lead (TWA) of 39 (12.0) µg/dl. Copy and delay organisation scores, surrogates for executive functions, were developed for ROCF-C and ROCF-DR. We used multiple regression analyses to examine the relationship between TWA and ROCF performance, organisational scores, and the interaction of organisational scores and TWA after adjusting for relevant covariates. RESULTS: Organisational scores, while not associated with years of education, were significantly correlated with ROCF-C and ROCF-DR performance. We found a significant relationship between TWA and ROCF-DR but not with ROCF-C performance. The interactions of TWA by copy organisation and TWA by delay organisation were significant for ROCF-DR with a significant dose-effect relationship only in participants with lower organisational scores. CONCLUSIONS: Chronic lead exposure was significantly associated with complex figure test delayed recall but not copy performance. Organisational strategies, a component of executive functions, served as effect modifiers of the relationship between lead exposure and non-verbal memory. With increasing TWA exposure workers with good organisational strategies maintained performance on the complex figure test while workers with poor organisational strategies demonstrated decreasing performance.

The evolution of disability in Parkinson disease.

The objectives of this study are to assess the level of disease severity associated with disability in Parkinson disease (PD) and the sequence of loss of independence in basic and instrumental activities of daily living (ADLs and IADLs). Six hundred eighteen patients with PD were evaluated for disease severity with the Unified PD Rating Scale (UPDRS) and for disability with the Older Americans Resource and Services Disability Subscale (OARS). The association between patient-reported disability on ADLs and IADLs and level of disease severity on the total UPDRS was examined cross-sectionally. Disability, with loss of independent function is reported between total UPDRS scores 30 to 40, and HY stages II to III. Difficulty with daily activities, without loss of independent function is reported earlier, at UPDRS <20 and HY I to II. Difficulty with walking is initially reported, followed by problems with a number of gait-dependent activities including housework, dressing, transferring in and out of bed, and traveling in the community. The transition from HY stage II to III marks a pivotal milestone in PD, when gait and balance impairment results in disability in many gait-dependent activities. The onset of disability in PD can be identified by asking patients about their walking, housework, dressing, and traveling. While individual patients vary in progression, the benchmarks of disability in this study provide guidance when counseling patients about prognosis. Better understanding of the stages of disability may facilitate the development of novel outcome measures in clinical trials in PD.

Impact of psychogenic movement disorders versus Parkinson's on disability, quality of life, and psychopathology.

Patients with psychogenic movement disorders (PMD) often report severe impairment, yet the impact of PMD on disability and quality of life has not been examined. We compared 66 patients with PMD and 704 patients with Parkinson's disease (PD) on measures of disability (Older Americans Resources and Services Scale, OARS); quality of life (QOL; SF-12v2 Health Survey) and psychiatric symptomatology (Brief Symptom Inventory 18, BSI-18). On the total OARS, PMD and PD patients reported similar levels of disability (17.6 +/- 6.6, 19.8 +/- 10.9, P = 0.490 at "best" function and 24.1 +/- 11.2, 26.2 +/- 14.3, P = 0.497 at their "worst" function). PMD patients reported similar Physical Health QOL to PD patients (38.9 +/- 14.5, 39.8 +/- 11.6, P = 0.652) but worse mental health QOL (41.6 +/- 13.4 vs. 48.9 +/- 11.0, P < 0.001). On the BSI-18, PMD patients reported higher levels of distress on the Global Symptom Index (62.03 +/- 9.6 vs. 53.7 +/- 9.9, P < 0.001) and on Anxiety, Depression and Somatization subscales (PMD vs. PD scores: Anxiety 58.9 +/- 12.0 vs. 52.3 +/- 10.1, P < 0.001; Depression 58.8 +/- 11.9 vs. 51.3 +/- 10.3, P < 0.001; Somatization 60.5 +/- 11.0 vs. 54.7 +/- 8.7, P < 0.001). Thus, severity of disability reported by the PMD group was equal to that seen in a progressive neurodegenerative condition. Quality of life and mental health implications of PMD were also evident. PMD impacts several aspects of patient function and daily life.

The association of lead exposure and motor performance mediated by cerebral white matter change.

The goals were to determine if lead exposure is associated with cerebral white matter changes (WMC) and if so, does WMC mediate the relation between lead and psychomotor slowing as measured by Grooved Pegboard (GP). In the literature, age is the strongest predictor of WMC and therefore 61 lead smelter workers age 50 and under were included in the study population. Mean (range) age was 40 (23-50) years, years of education was 9 (0-13), duration of employment was 19 (1-26), current blood lead (PbB) was 29 (16-42) microg/dl, working lifetime weighted integrated blood lead (IBL) was 826 (65-1451) microg year/dl, working lifetime weighted average blood lead (TWA) was 42 (17-59) microg/dl, and bone lead (PbBn) was 39 (-12-90) microg Pb/g bone mineral. WMC, recorded as hyperintensities on T2-weighted MRI of the brain were graded. Lead variables were entered in a logistic regression attempting to differentiate normal versus abnormal MRI, after controlling for age and cerebrovascular risk factors. Direct effects of lead on GP and indirect effects of lead on GP through WMC was modeled using multiple linear regression analyses after controlling for the covariates. WMC were present in 23% of MRIs. Logistic regression of WMC on lead exposure metrics demonstrated significantly elevated odds ratios for IBL, TWA, and PbBn after the covariates. Of the lead exposure variables, IBL (beta=0.339, p<0.10) had a larger direct effect on GP after adjusting for the covariates than PbBn (beta=0.265, p<0.10). After adjusting for the lead term and covariates WMC accounted for an additional effect on GP performance after PbBn (beta=0.261, p<0.10) and after IBL (beta=0.278, p<0.05). Path analysis demonstrated that some of the relationship of both PbBn and IBL with GP is mediated by WMC.

Subjective report versus objective measurement of activities of daily living in Parkinson's disease.

We compared subjective self-reports with objective performance ratings of activities of daily living (ADLs) and instrumental ADLs (IADLs) in patients with Parkinson's disease (PD) and identified variables associated with discordance of ratings between these two methods. Seventy-six PD patients completed a modified Older Americans Resources and Services scale, assessing ADLs and IADLs. These results were compared with structured performance tests of walking, eating, dressing, money, and medicine management administered in the clinic. Patient performance was rated on a five-point Likert-type scale, ranging from 1 = no difficulty to 5 = completely unable to perform task. Significant differences were found between patients and clinicians' ratings on all tasks except walking. On the other four tasks, paired group t tests showed that patients reported better function compared with the clinician rating of medication management (1.33 vs. 2.80), eating (1.53 vs. 1.76), dressing (1.64 vs. 1.86), and managing money (1.44 vs. 2.06). A discrepancy was found between patients subjective reporting of ADL and IADL function and objective ratings. Patients overestimated their function on four of five tasks. Further study is necessary to identify whether subjective or objective performance ratings are more reflective of actual daily function.

Effect of lead exposure and ergonomic stressors on peripheral nerve function.

In this study we investigated the effect of recent and chronic lead exposure, and its interaction with ergonomic stressors, on peripheral nerve function. In a cross-sectional design, we used retrospective exposure data on 74 primary lead smelter workers. We measured blood and bone lead levels and, from historical records, calculated lead dose metrics reflecting cumulative lead exposure: working-lifetime integrated blood lead (IBL) and working-lifetime weighted-average blood lead (TWA). We additionally created five metrics related to IBL that cumulated exposure only above increasing blood lead levels ranging from 20 to 60 microg/dL (IBL20-IBL60). Current perception threshold (CPT) assessed large myelinated (CPT2000), small myelinated (CPT250), and unmyelinated (CPT5) sensory nerve fibers. Using multiple linear regression, we modeled CPT on the different measures of lead dose after adjusting for relevant covariates. CPT had a curvilinear relationship with TWA, with a minimum at a TWA of 28 microg/dL. Both TWA and IBL accounted for a significant percentage of the variance of CPT2000 (DeltaR2 = 8.7% and 3.9%, respectively). As the criterion blood lead level increased from IBL20 through IBL60, so did the percentage of CPT2000 variance explained, with DeltaR2 ranging from 5.8% (p < 0.03) for IBL20 to 23.3% (p < 0.00) for IBL60. IBL60 also significantly contributed to the explanation of variance of CPT250 and significantly interacted with ergonomic stressors. Measures of chronic blood lead exposure are associated with impairment of large and small myelinated sensory nerve fibers. This effect is enhanced at the highest doses by ergonomic stressors.