Cartas al editor

The literature suggests that body kinematics and musculoskeletal differences are major factors contributing to the high disparity in non-contact Anterior Cruciate Ligament (ACL) injury rate between genders. The literature also indicates that the incidence of non-contact ACL injury predominates during single-leg landing sports such as basketball, soccer, and handball. Despite this, there are few studies investigating kinematics or musculoskeletal differences between genders during single-leg landing from increasing vertical heights and horizontal distances. The objectives of this study are threefold: first, conduct a gap study identifying the barriers to predicting mechanisms and risk factors for non-contact ACL injury. Second, propose a new approach that can address some of the challenges encountered in some existing non-contact ACL injury study approaches. Finally, whilst determining whether or not gender differences explain the higher rate of ACL injuries among females, identify and correlate the biomechanical and musculoskeletal variables significantly impacted by gender, vertical landing height, and/or horizontal landing distance and their interactions to various ACL injury risk predictor variables during single-leg landing. Experiments using male and female subjects, inverse dynamics analysis using Visual3D, and musculoskeletal modeling simulation using AnyBody Modeling System were approaches used to explore these objectives. Salient findings from this dissertation includes but are not limited to, non-contact ACL injury that occurs during single-leg landing is mutifaceted entailing many factors that cannot be captured in any one existing ACL injury study approach. Non-contact ACL injury during single-leg landing may not be gender specific. Both vertical height and horizontal distance of landing increase the risk of non-contact ACL injury during single-leg landing. Body kinematics during single-leg landing may not be the sole determinant in attenuating ground reaction forces and consequently risk of ACL injury. The hamstring and gastrocnemius muscles were determined to strain shield the ACL while the quadriceps were found to have no significant effect on risk of ACL injury during single-leg landing. Within the findings and limitations of this study the knowledge garnered from this research may aid in tailoring future studies so as to enable more robust non-contact ACL injury prevention protocols.

No description available.

This thesis involves a comprehensive review of the personality, psychiatric, and genetic risk factors for alcoholism and drug abuse. Based on this review, it is hypothesised that specific risk factors cluster together to represent separate vulnerability pathways to substance abuse and that differential susceptibility to the pharmacological effects of drugs of abuse (reinforcement and intoxication) mediates the relationship between such risk characteristics and drug-taking behaviour. A series of four studies are presented indicating that groups of individuals characterized by different risk factors for alcoholism are differentially sensitive to the reinforcing properties of alcohol. Non-alcoholic young adult men presumed to be at genetic risk for alcoholism (due to high genetic loading for alcoholism) were shown to be sensitive to the effects of alcohol on resting and stress-induced physiological states hypothesized to reflect activity within a brain reward system involved in the activation of approach and avoidance behaviour. Non-alcoholic young adult males self-reporting a personality profile that has been associated with increased risk for the development of panic disorder also demonstrated idiosyncratic responses to alcohol intoxication in that they appeared particularly sensitive to the. fear-dampening effects of alcohol. Finally, a group of non-alcoholic males were identified as being particularly susceptible to elevated and problematic alcohol and drug use in early adulthood due to a disinhibited/antisocial personality profile. These findings were interpreted as reflecting separate vulnerability pathways to substance use/abuse in which differential sensitivity to drug reinforcement and disinhibited personality are thought to play an important role in determining liability to seek out behavioural reinforcement from drugs of abuse. A second set of studies tested whether these factors are implicated in the maintenance of problematic alcohol and drug consumptio

No description available.

No description available.

MSC (Med),Population-Based Epidemiology, Faculty of Health Sciences, University of the Witwatersrand, 2007 / Objective To compare risk factors between HIV-positive concordant and discordant couples. Study design This is a cross-sectional secondary data analysis study using data from Africa Centre Demographic Information System (ACDIS) database (June 2003 to December 2004) and data from the first round of population-based HIV surveillance conducted by the Africa Centre for Health and Population Studies. Methods Eighty-five HIV-positive concordant couples (both partners were HIV-positive) and 73 discordant couples (one partner was HIV-positive and other partner HIV-negative) were identified and selected from the first round of population-based HIV surveillance conducted from June 2003 to December 2004 in Hlabisa Demographic Surveillance System site. Partners health and sexual behaviour data were collected together with the blood sample for HIV test during the same round. Socio-economic and demographic data of partners were obtained from the ACDIS database and were collected within the same period (June 2003 to December 2004). The behavioural, biological, demographic and socio-economic risk factors for HIVpositive concordance and transmission within discordant couples were analysed. Circumcision and area of residence respectively were the biological and demographic factors considered. Number of household assets was used as a proxy for socioeconomic status. The behavioural factors considered were male condom-use, sexual debut (age at first sex), number of lifetime partners and premarital partners. The age and educational level of partners were considered as potential confounders. 5 RESULTS The uncircumcised men were more likely to be in HIV-positive concordant couples than to be in discordant couples (OR =10.8, 95% CI [1.93 – 60.30], p=0.007). Partners living in urban area were 4.7 times more at risk of being in a HIV-positive concordant relationship than to be in discordant relationship (OR=4.7, 95% CI [2.09 - 10.39], p<0.001). Male not using condom on regular basis with female partners, early sexual debut, greater number of premarital partners, household assets and lifetime partners were found not to be significantly associated with HIV-positive concordance. Conclusion There are several biologic, socio-economic, demographic and behavioural risk factors for HIV-positive concordance. However, identifying some of them might be used to address transmission of HIV among discordant couples through intervention programs. Although cross-sectional studies are not ideal for establishing temporality, this study corroborates the findings of other studies that living in urban areas and circumcision are associated with HIV transmission.

A number of risks have been proposed in the literature to be associated with hyperfunctional voice disorder (HVD), one of the most common communication disorders. Yet, it is not distributed randomly in the population, certain population groups are at higher risks of developing voice disorders. It is generally agreed that the development of voice disorders involves a multifactorial genesis. The study of risks has been documented in different diseases and also in the World Health Report (W.H.O., 2002). The probabilistic approach has been recommended to effectively manage the likelihood of health outcome in relations to disease development (Tonetti, 1988) and systematically devise prevention and intervention programs targeting population at risk. Yet, in the study of the development of HVD, the lack of a universally agreed theoretical framework prohibited the establishment of such structure and research on advancement on preventive programs. The present thesis aimed to investigate the adoption of the FMAT risk assessment framework based on the probabilistic approach (WHO) to the field of hyperfunctional voice disorders. A Voice Risk Calculator (VRC) Questionnaire was developed focusing on the vocal loading, physiological/medical and psycho-emotional indicators and all subjects completed this questionnaire. The VRC Questionnaire was then validated based on the FMAT framework using a cross-sectional study was used to identify risk indicators associated with HVD development in the local population and a longitudinal study was employed to validate these risk indicators as risk factors. A total of 192 Cantonese-speaking subjects participated in the cross-sectional study including 123 dysphonic subjects and 69 non-dysphonic control subjects and 7 in the longitudinal study. Instrumental measurements including the voice range profile, aerodynamic measurements and the Voice Activity and Participation Profile (VAPP, Ma & Yiu, 2001) were also used as part of the validation procedure. The findings showed that significant differences were found between the dysphonic and non-dysphonic group in the cross-sectional study based on results from the instrumental measurements protocol. A minimal set of selected VRC questionnaire items were also determined (Items 1, 3, 25 and somatization scale) to differences between the subject groups in this study. Thus a set of locally-applicable risk indicators have been suggested. Yet, only minimal changes have been detected in a high-risk group targeted in the longitudinal study. Research (Beck, 1994) indicated that disease progression takes over a time frame of at least more than two years. Thus the small subject size and temporal element of the longitudinal study in the present thesis limited research aim to be achieved. Nonetheless that first phase of the FMAT framework for hyperfunctional voice disorders have been established in the current study and a finalized version of the Voice Risk Calculated Questionnaire has been developed for future research. / published_or_final_version / Speech and Hearing Sciences / Doctoral / Doctor of Philosophy

Background: The epidemic of childhood obesity is of increasing public health concern, with major implications for long-term health. Prevention strategies are urgently needed. Most of the evidence concerning risk factors for childhood obesity comes from observational studies, mainly from Western populations. In the West, socio-economic position (SEP) is often associated with potential risk factors and with childhood obesity, making these observational studies open to residual confounding. Evidence from a setting with a different confounding structure can be valuable in disentangling whether associations observed in Western settings reflect potentially reversible causal effects of risk factor or are confounded by SEP. Objectives: This thesis took advantage of a large (n=8327), population-representative Chinese birth cohort from a developed non-Western setting, Hong Kong, where the confounding structure between potential risk factors and childhood obesity is different, to examine the association of four modifiable risk factors (mode of delivery, the timing of solid food introduction, type of child care and dairy product consumption) with adiposity from infancy to early puberty. Methods: Adiposity from infancy to early puberty was proxied by age- and sex-specific body mass index (BMI) standardized scores (z-scores) from 3 months to 13 years, relative to the 2006 World Health Organization (WHO) child growth standards for 0-5 years and the 2007 WHO growth reference for 5-19 years. Overweight (including obesity) was defined according to International Obesity Task Force cut-off. I compared three marginal models (maximum likelihood estimation, generalized estimating equations and quantile regression) to ascertain the optimal way of modeling the population-averaged association of early life risk factors with BMI z-score because of the complex data structure with inevitably some missing data. All three methods were used to examine the adjusted associations of mode of delivery and the timing of solid food introduction with BMI z-score from infancy to early puberty and with overweight (including obesity) from early childhood to early puberty. Multivariable linear and logistic regression were used to examine the adjusted associations of the type of child care at 6 months, 3 years, 5 years and 11 years with BMI z-score and overweight (including obesity) at 13 years, and the association of dairy product consumption at 11 years with BMI z-score at 13 years. Results: My analyses were robust to the choice of marginal model. Mode of delivery, the timing of solid food introduction and dairy product consumption were not associated BMI z-score or overweight (including obesity), but informal child care was associated with higher BMI z-score and overweight at early puberty. Conclusions: In this population-representative birth cohort from an understudied non- Western developed setting with little patterning of childhood adiposity by SEP, informal child care (by family members and/or in-home employed help) may be a target for intervention. Conversely, cesarean section, early introduction of solid food and lack of dairy product consumption do not appear to be contributing to the current obesity epidemic. Non-replication in a different context suggests some observed associations in the West may be indicators of residual confounding rather than of causality. / published_or_final_version / Public Health / Doctoral / Doctor of Philosophy

Introduction.  Despite being thought of as common and having serious consequences, falls have not been extensively studied in Parkinson’s disease (PD).  Prior to this study commencing there were no published large-scale prospective studies looking at the risk factors for falls in PD.  This study aimed to accurately establish the incidence of falls in PD and investigate predictive risk factors for fallers from baseline data in all patients known to a district general hospital PD service.  In addition cardiovascular investigation, autonomic function and osteoporosis in PD were assessed. Methods.  Baseline data was gathered on a cohort of 109 patients with idiopathic PD and the number of falls prospectively ascertained over the following year.  The multidisciplinary baseline assessment included historical data, disease specific rating scales, physiotherapy assessment, tests of visual, cardiovascular and autonomic function and bone densitometry. Results.  Falls occurred in 68.3% of the subjects. Previous falls, disease duration and loss of armswing were independent predictors of falls and recurrent falls.  There were also statistically significant associations between disease severity, balance impairment, depression cognitive impairment and falling.  Males were more likely to suffer from recurrent falls.  Cardiovascular disorders, autonomic dysfunction and osteoporosis were also highly prevalent but not associated with falls. Conclusions.    Falls are a common problem in PD.  Some of the risk factors are potentially modifiable.  Although there are intrinsic factors inherent to PD that can cause falls, patients with PD that fall should be thoroughly assessed to look more closely at the reason for falling in those individuals.  Potential primary prevention of falls should be considered in all patients with PD.  In the future, multi-centre intervention studies will be necessary to further investigate potential methods of decreasing falls and their effects in PD.