Paul Succop

Biomechanical Measures of Neuromuscular Control and Valgus Loading of the Knee Predict Anterior Cruciate Ligament Injury Risk in Female Athletes A Prospective Study

Background Female athletes participating in high-risk sports suffer anterior cruciate ligament injury at a 4- to 6-fold greater rate than do male athletes. Hypothesis Prescreened female athletes with subsequent anterior cruciate ligament injury will demonstrate decreased neuromuscular control and increased valgus joint loading, predicting anterior cruciate ligament injury risk. Study Design Cohort study; Level of evidence, 2. Methods There were 205 female athletes in the high-risk sports of soccer, basketball, and volleyball prospectively measured for neuromuscular control using 3-dimensional kinematics (joint angles) and joint loads using kinetics (joint moments) during a jump-landing task. Analysis of variance as well as linear and logistic regression were used to isolate predictors of risk in athletes who subsequently ruptured the anterior cruciate ligament. Results Nine athletes had a confirmed anterior cruciate ligament rupture; these 9 had significantly different knee posture and loading compared to the 196 who did not have anterior cruciate ligament rupture. Knee abduction angle (P <. 05) at landing was 8° greater in anterior cruciate ligament-injured than in uninjured athletes. Anterior cruciate ligament-injured athletes had a 2.5 times greater knee abduction moment (P <. 001) and 20% higher ground reaction force (P <. 05), whereas stance time was 16% shorter; hence, increased motion, force, and moments occurred more quickly. Knee abduction moment predicted anterior cruciate ligament injury status with 73% specificity and 78% sensitivity; dynamic valgus measures showed a predictive r2 of 0.88. Conclusion Knee motion and knee loading during a landing task are predictors of anterior cruciate ligament injury risk in female athletes. Clinical Relevance Female athletes with increased dynamic valgus and high abduction loads are at increased risk of anterior cruciate ligament injury. The methods developed may be used to monitor neuromuscular control of the knee joint and may help develop simpler measures of neuromuscular control that can be used to direct female athletes to more effective, targeted interventions.

Early exposure to lead and juvenile delinquency.

Cross-sectional studies have reported an association between lead (Pb) levels in bone and delinquent behavior in later childhood and adolescence. This is the first prospective longitudinal study of Pb and child development to address this question with comprehensive assessments of toxicant exposure and other developmental cofactors. A prospective longitudinal birth cohort of 195 urban, inner-city adolescents recruited between 1979 and 1985 was examined. Relationships between prenatal and postnatal exposure to Pb (serial blood Pb determinations) and antisocial and delinquent behaviors (self- and parental reports) were examined. Prenatal exposure to Pb was significantly associated with a covariate-adjusted increase in the frequency of parent-reported delinquent and antisocial behaviors, while prenatal and postnatal exposure to Pb was significantly associated with a covariate-adjusted increase in frequency of self-reported delinquent and antisocial behaviors, including marijuana use. Use of marijuana itself by Cincinnati Lead Study (CLS) teens was strongly associated with all measures of delinquent and antisocial behavior. This prospective longitudinal study confirmed earlier clinical observations and recent retrospective studies that have linked Pb exposure with antisocial behavior in children and adolescents. Both prenatal and postnatal exposure to Pb were associated with reported antisocial acts and may play a measurable role in the epigenesis of behavioral problems independent of the other social and biomedical cofactors assessed in this study.

The developmental consequences of low to moderate prenatal and postnatal lead exposure: intellectual attainment in the Cincinnati Lead Study Cohort following school entry.

In a further follow-up study of the Cincinnati Lead Study Cohort, 253 children were administered the Wechsler Intelligence Scale for Children-Revised (WISC-R) at approximately 6.5 years of age. Postnatal blood lead concentrations were inversely associated with Full-Scale (FSIQ) and Performance IQ (PIQ). Following statistical adjustment for developmental co-factors such as maternal IQ and an assessment of the quality of caretaking in the home environment, a statistically significant relationship remained between postnatal blood lead concentrations and PIQ. Further statistical analyses suggested that averaged lifetime blood lead concentrations in excess of 20 micrograms/dL were associated with deficits in PIQ on the order of approximately 7 points when compared to children with mean concentrations less or equal to 10 micrograms/dL. These results are discussed in terms of their consistency with other similar studies as well as their internal consistency with earlier reports on this cohort. The findings of this investigation support recent initiatives in the United States to reduce the exposure of children to environmental lead.

Pubertal Assessment Method and Baseline Characteristics in a Mixed Longitudinal Study of Girls

OBJECTIVES: The objective of this study was to describe the assessment methods and maturation status for a multisite cohort of girls at baseline recruitment and at ages 7 and 8 years. METHODS: The method for pubertal maturation staging was developed collaboratively across 3 sites. Girls at ages 6 to 8 years were recruited at 3 sites: East Harlem, New York; greater Cincinnati metropolitan area; and San Francisco Bay area, California. Baseline characteristics were obtained through interviews with caregivers and anthropometric measurements by trained examiners; breast stage 2 was defined as onset of pubertal maturation. The κ statistic was used to evaluate agreement between master trainers and examiners. Logistic regression models were used to identify factors that are associated with pubertal maturation and linear regression models to examine factors that are associated with height velocity. RESULTS: The baseline cohort included 1239 girls. The proportion of girls who had attained breast stage 2 varied by age, race/ethnicity, BMI percentile, and site. At 7 years, 10.4% of white, 23.4% of black non-Hispanic, and 14.9% of Hispanic girls had attained breast stage ≥2; at 8 years, 18.3%, 42.9%, and 30.9%, respectively, had attained breast stage ≥2. The prime determinant of height velocity was pubertal status. CONCLUSIONS: In this multisite study, there was substantial agreement regarding pubertal staging between examiners across sites. The proportion of girls who had breast development at ages 7 and 8 years, particularly among white girls, is greater than that reported from studies of girls who were born 10 to 30 years earlier.

Obesity and Presenteeism: The Impact of Body Mass Index on Workplace Productivity

Objective: To examine whether obesity is associated with increased presenteeism (health-related limitations at work). Methods: Randomly selected manufacturing employees (n = 341) were assessed via height and weight measures, demographic survey, wage data, and the Work Limitations Questionnaire. The Work Limitations Questionnaire measures productivity on four dimensions. Analyses of variance and analyses of covariance were computed to identify productivity differences based on body mass index (BMI). Results: Moderately or extremely obese workers (BMI ≥35) experienced the greatest health-related work limitations, specifically regarding time needed to complete tasks and ability to perform physical job demands. These workers experienced a 4.2% health-related loss in productivity, 1.18% more than all other employees, which equates to an additional

Lead exposure and the cognitive development of urban preschool children: The cincinnati lead study cohort at age 4 years

506 annually in lost productivity per worker. Conclusions: The relationship between BMI and presenteeism is characterized by a threshold effect, where extremely or moderately obese workers are significantly less productive than mildly obese workers.

Cancer Risk Among Firefighters: A Review and Meta-analysis of 32 Studies

The purpose of this analysis was to determine if significant associations could be observed between prenatal/postnatal blood lead (PbB) levels and the cognitive development of 258 urban, inner-city children at 4 years of age. These children have been followed since birth with frequent assessments of general health, PbB, and neuropsychological status. The Kaufman Assessment Battery for Children (K-ABC) was administered at approximately 4 years of age. Higher neonatal PbB levels were associated with poorer performance on all K-ABC subscales. However, this inverse association was limited to children from the poorest families. Maternal PbB levels were unrelated to 4-year cognitive status. Few statistically significant associations between postnatal PbB levels and K-ABC scales could be found. However, the results did suggest a weak inverse relationship between postnatal PbB levels and performance on a K-ABC subscale which assesses visual-spatial and visual-motor integration skills. In these results we note both contradiction and accord with previously published prospective studies.

Early exposure to lead and neuropsychological outcome in adolescence

Objective: The objective of this study was to review 32 studies on firefighters and to quantitatively and qualitatively determine the cancer risk using a meta-analysis. Methods: A comprehensive search of computerized databases and bibliographies from identified articles was performed. Three criteria used to assess the probable, possible, or unlikely risk for 21 cancers included pattern of meta-relative risks, study type, and heterogeneity testing. Results: The findings indicated that firefighters had a probable cancer risk for multiple myeloma with a summary risk estimate (SRE) of 1.53 and 95% confidence interval (CI) of 1.21–1.94, non-Hodgkin lymphoma (SRE = 1.51, 95% CI = 1.31–1.73), and prostate (SRE = 1.28; 95% CI = 1.15–1.43). Testicular cancer was upgraded to probable because it had the highest summary risk estimate (SRE = 2.02; 95% CI = 1.30–3.13). Eight additional cancers were listed as having a “possible” association with firefighting. Conclusions: Our results confirm previous findings of an elevated metarelative risk for multiple myeloma among firefighters. In addition, a probable association with non-Hodgkin lymphoma, prostate, and testicular cancer was demonstrated.

Development and Validation of a Clinic-Based Prediction Tool to Identify Female Athletes at High Risk for Anterior Cruciate Ligament Injury

One hundred and ninety-five participants in the Cincinnati Lead Study were neuropsychologically evaluated in mid-adolescence. The neuropsychological measures yielded five factors labeled Memory, Learning/IQ, Attention, Visuoconstruction, and Fine-Motor. Prenatal, Average Childhood, and 78 month blood lead (PbB) levels were used in a series of multiple regression analyses. Following rigorous covariate pretesting and adjustment, a significant main effect of 78 month PbB on the Fine-Motor factor was found (p <.004). Significant interactions were also found between gender and lead exposure parameters for both Attention and Visuoconstruction indicating heightened risk in males. Finally, a trend toward significance was found for the PbB x SES interaction for Learning/IQ, consistent with previous evidence of increased educational and cognitive vulnerability for youth from more disadvantaged backgrounds. These results provide new evidence from the longest continuing prospective study of the remote effects of early lead exposure. They indicate the presence of selective neuropsychological effects in this population, and also that males and females are not uniformly affected. These results also underscore the complexity of models of neurobehavioral development, and the modest predictive power of any single determinant.

Onset of Breast Development in a Longitudinal Cohort

Background Prospective measures of high knee abduction moment (KAM) during landing identify female athletes at high risk for anterior cruciate ligament injury. Laboratory-based measurements demonstrate 90% accuracy in prediction of high KAM. Clinic-based prediction algorithms that employ correlates derived from laboratory-based measurements also demonstrate high accuracy for prediction of high KAM mechanics during landing. Hypotheses Clinic-based measures derived from highly predictive laboratory-based models are valid for the accurate prediction of high KAM status, and simultaneous measurements using laboratory-based and clinic-based techniques highly correlate. Study Design Cohort study (diagnosis); Level of evidence, 2. Methods One hundred female athletes (basketball, soccer, volleyball players) were tested using laboratory-based measures to confirm the validity of identified laboratory-based correlate variables to clinic-based measures included in a prediction algorithm to determine high KAM status. To analyze selected clinic-based surrogate predictors, another cohort of 20 female athletes was simultaneously tested with both clinic-based and laboratory-based measures. Results The prediction model (odds ratio: 95% confidence interval), derived from laboratory-based surrogates including (1) knee valgus motion (1.59: 1.17-2.16 cm), (2) knee flexion range of motion (0.94: 0.89°-1.00°), (3) body mass (0.98: 0.94-1.03 kg), (4) tibia length (1.55: 1.20-2.07 cm), and (5) quadriceps-to-hamstrings ratio (1.70: 0.48%-6.0%), predicted high KAM status with 84% sensitivity and 67% specificity (P < .001). Clinic-based techniques that used a calibrated physicians scale, a standard measuring tape, standard camcorder, ImageJ software, and an isokinetic dynamometer showed high correlation (knee valgus motion, r = .87; knee flexion range of motion, r = .95; and tibia length, r = .98) to simultaneous laboratory-based measurements. Body mass and quadriceps-to-hamstrings ratio were included in both methodologies and therefore had r values of 1.0. Conclusion Clinically obtainable measures of increased knee valgus, knee flexion range of motion, body mass, tibia length, and quadriceps-to-hamstrings ratio predict high KAM status in female athletes with high sensitivity and specificity. Female athletes who demonstrate high KAM landing mechanics are at increased risk for anterior cruciate ligament injury and are more likely to benefit from neuromuscular training targeted to this risk factor. Use of the developed clinic-based assessment tool may facilitate high-risk athletes’ entry into appropriate interventions that will have greater potential to reduce their injury risk.