Maximum likelihood estimation procedures for categorical data

Please read the abstract in the section, 00front, of this documentDissertation (MSc (Mathematical Statistics))--University of Pretoria, 2005.Mathematics and Applied Mathematicsunrestricte

Changes in the mandibular angle during adulthood in South Africans

OBJECTIVES : The purpose of this study was to measure the mandibular angle as a reflection of the biomechanical forces acting on the mandible and relate it to aging and loss of teeth. METHODS : A total of 717 mandibles of adult individuals were selected from the Pretoria Bone Collection. These mandibles were allocated to dentition subgroups according to their pattern of tooth loss. The angle of the mandible was measured with a mandibulometer. The variation in the mandibular angle was statistically analyzed by age regressions and comparisons between adjusted means of dentition subgroups. RESULTS : Aging per se was not associated with a greater mandibular angle. With limited tooth loss, aging was associated with a smaller mandibular angle in females. Generally the mandibular angle increased with tooth loss and was accentuated when an even occlusion pattern was lost rather than with more extensive tooth loss. A more pronounced increase in mandibular angle with tooth loss was noted in females and individuals of European ancestry. CONCLUSIONS : Tooth loss and not aging is associated with an increase in the mandibular angle. Masculinity and being from African ancestry provided some protection against an increase in the mandibular angle with tooth loss. The accentuated increase in the mandibular angle when an even occlusion pattern was disturbed supports the notion that an uneven loss of teeth was indeed associated with inefficient mastication. The unexpected decrease in angle noted in females with aging but limited tooth loss may be indicative of constructive changes beyond puberty.http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1520-63002017-09-30hb2016AnatomyStatistic

Adult female rape survivors' views about the constitutional, human rights and compulsory HIV testing of alleged sex offenders

The reality of rape as a direct form of contact crime remains deeply entrenched in South African communities, despite numerous efforts from various governmental stakeholders to curb this heinous crime. The Criminal Law (Sexual Offences and Related Matters) Amendment Act (32 of 2007), came into effect in 2007 as a strategic approach to prevent secondary victimisation of a victim of sexual offence through the Criminal Justice System (CJS). One of the strategies employed in the aforementioned Act, is the compulsory Human Immunodeficiency Virus (HIV) testing of alleged sex offenders. The compulsory HIV testing of an alleged sex offender evoked controversy pertaining to its efficiency and the human rights violations that might be incurred upon the alleged accused. This article will highlight the subjective perceptions of adult female rape survivors towards their rights and the rights of alleged sex offenders following rape. The research was conducted at four Thuthuzela Care Centres (TCCs) in the Gauteng province, which are one stop multi-disciplinary state-owned facilities providing medico-legal services for victims of sexual offences in South Africa. The study was exploratory- descriptive in nature within a positivistic paradigm. Quantitative research methods were employed, with the aid of a self-administered questionnaire as a measuring instrument given to adult female rape survivors to complete. Forty-five research respondents participated in the study. This article thus serves as one of two domains under investigation relating to the current study.http://www.crimsa.ac.za/acta.htmlam2016Social Work and CriminologyStatistic

The crime-related views of first-year criminology students attending two parallel-medium South African universities

In addition to the provision of tertiary education, Institutions of Higher Education are expected to instil critical and independent thinking skills in students. Students often bring into the learning environment their own subjective views about the world they live in. We conducted a self-administered survey among 867 first-year students registered for Criminology at two parallel-medium universities (University of the Freestate and the University of Pretoria). The aim of the study was to determine their views and perceptions about the crime phenomenon in South Africa. The survey was undertaken at the beginning of the academic year in order to minimise the possible influence of academic modules on their views and perceptions. Tests of significance (chi-square and effect size) revealed some differences in respect of the gender of students. However, significant differences mostly featured across population groups, in particular between African and White students’ views about personal safety and vulnerability to crime, the causes of crime, sentencing, law enforcement and imprisonment. In terms of the careers that students wish to pursue, differences in views appear to be influenced by their backgrounds instead of the professions they aim to fill. The findings call on Criminology lecturers to incorporate materials in their curricula that will challenge the misconceptions students may hold about crime in South Africa. In addition, platforms are needed where students can confront their own assumptions and existing beliefs about crime, ultimately to strengthen social cognition in this domain. Such activities could prove difficult in parallel-medium institutions where the languages of tuition create two discernible student profiles. Follow-up research is needed to gauge the impact of tertiary education on the crime-related views and perceptions of students.http://www.crimsa.ac.za/am2013gv201

End-of-life decision-making capacity in older people with serious mental illness

BACKGROUND : The study’s main aim was to assess the end-of-life decision-making capacity and health-related values of older people with serious mental illness. METHODS : A cross-sectional, observational study, was done at Weskoppies Psychiatric Hospital, Gauteng Province, South Africa that included 100 adults older than 60 years of age and diagnosed with serious mental illness. The Mini-Cog and a semi-structured clinical assessment of end-of-life decision-making capacity was done before a standardized interview, Assessment of Capacity to Consent to Treatment, was administered. This standardized instrument uses a hypothetical vignette to assess decision-making capacity and explores healthcare-related values. RESULTS : The Assessment of Capacity to Consent to Treatment scores correlated (p < 0.001) with the outcomes of the semi-structured decision-making capacity evaluation. Significant correlations with impaired decision-making capacity included: lower scores on the Mini-Cog (p < 0.001); a duration of serious mental illness of 30–39 years (p = 0025); having a diagnosis of schizophrenia spectrum disorders (p = 0.0007); and being admitted involuntarily (p < 0.0001). A main finding was that 65% of participants had decision-making capacity for end-of-life decisions, were able to express their values and engage in advance care discussions. DISCUSSION AND CONCLUSION : Healthcare providers have a duty to initiate advance care discussions, optimize decision-making capacity, and protect autonomous decision-making. Many older patients with serious mental illness can engage in end-of-life discussions and can make autonomous decisions about preferred end-of-life care. Chronological age or diagnostic categories should never be used as reasons for discrimination, and older people with serious mental illness should receive end-of-life care in keeping with their preferences and values.http://www.frontiersin.org/Psychiatryam2022PsychiatryStatistic

Increased risk of suicide in schizophrenia patients with linkage to chromosome 13q

We link schizophrenia in families from the genetically isolated South African Afrikaner population to chromosome 13q (n =51), 1p (n =23) and combined 13q & 1p (n =18). Patients with linkages to chromosome 13q were 4.16 times more likely to meet diagnostic criteria for schizoaffective disorder compared to patients with linkage to 1p. A third of patients with linkage to both 13q & 1p met diagnostic criteria for SAD. There was a significant positive relationship between suicidality and a diagnosis of schizoaffective disorder. Identifying linkage to chromosome 13q may be informative in identifying suicide risk early and prevent morbidity and mortality in schizophrenia patients.JL Roos is receiving incentive funding from the National Research Foundation (NRF).http://www.elsevier.com/locate/psychres2018-05-31hb2017PsychiatryStatistic

Phenotypic features of patients with schizophrenia carrying de novo gene mutations : a pilot study

Genome-wide scans have revealed a significant role for de novo copy number variants (CNVs) and Single Nucleotide variants (SNVs) in the genetic architecture of schizophrenia. The present study attempts to parse schizophrenia based on the presence of such de novo mutations and attempts genotype–phenotype correlation. We examined phenotypic variables across three broad categories: clinical presentation, premorbid function, disease course and functional outcome and compared them in individuals with schizophrenia carrying either a de novo CNV, a de novo SNV, or no de novo mutation. Work skills were worst affected in patients carrying de novo CNVs. More learning disabilities were found in subjects carrying de novo SNVs. Patients with either mutation had older parents at birth and worse functional outcome as measured by SLOF scores. We found no relation between treatment resistance and the presence of de novo mutations. The combined consideration of the functional outcome scores and early deviant behaviours was found to have higher predictive value for underlying genetic vulnerability. Due to the rare nature of the de novo mutations the sample sizes studied here were small. Despite this, valuable phenotypic characteristics were identified in schizophrenia patients carrying de novo mutations and studying larger samples will be of interest.http://www.elsevier.com/locate/psychreshb201

Platelet hyperactivity and fibrin clot structure in transient ischemic attack individuals in the presence of metabolic syndrome : a microscopy and thromboelastography (R) study

BACKGROUND : Strokes are commonly preceded by transient ischemic attacks (TIAs). TIA is often associated with metabolic syndrome (causing chronic inflammation), resulting in a proinflammatory- and procoagulantenvironment. The aim of this study was to determine whether platelet- and fibrin network-morphology or coagulation profiles of individuals that suffered a TIA in the presence of metabolic syndrome was altered when compared to healthy individuals. MATERIALS AND METHODS : The study consisted of 40 voluntary participants. Twenty individuals that suffered a TIA in the previous 48 h with at least two metabolic syndrome risk factors present and twenty healthy age-matched controls. Scanning electron- and atomic force microscopy was used to study platelet- and fibrin-morphology, atomic force microscopy was used to study platelet- and fibrin fiber-elasticity and thromboelastography® for the study of coagulation profiles. Statistical analysis was performed to compare the two groups. In all cases a p-value of less than 0.05 was considered statistically significant. RESULTS : Platelets of the control group appeared spherical with few pseudopodia present while the platelets of the TIA individuals presented with numerous pseudopodia and spreading, indicating activation. Platelet aggregation was also present. The fibrin networks of the healthy individuals consist of thick and thin fibers that form an organized network of fibers. The fibrin networks of the TIA individuals appeared less organized with less taut fibers. Fibrin fiber thickness was found to be significantly increased in the TIA group (p-value <0.001) when compared to healthy controls. The thicker fibers formed irregular networks with thick masses of fibrin fibers. Platelet and fibrin fiber elasticity was found to be significantly lower in the experimental group (p-value 0.0042 and p-value 0.0007 respectively). The hemostatic profiles of the diseased individuals did not differ significantly (p-value > 0.05) from the healthy controls, indicating a normal functioning coagulation cascade. CONCLUSION : The findings indicate that pathological clot formation is not caused by alterations in the coagulation cascade but rather by the premature activation of platelets (as a result of chronic inflammation) that in turn causes altered fibrin formation.National Research Foundation (NRF) South Africa: E Pretorius.am201

Family history identifies sporadic schizoaffective disorder as a subtype for genetic studies

BACKGROUND : Schizophrenia is a heterogeneous disorder with strong genetic vulnerability. Family history of schizophrenia has been considered in genetic studies under several models. De novo genetic events seem to play a larger role in sporadic cases. AIM : This study used the familial–sporadic distinction with the aim of identifying a more homogeneous phenotype to delineate the genetic and clinical complexity of schizophrenia. SETTING : The study was conducted at Weskoppies Hospital, Pretoria, South Africa. METHODS : The study included 384 participants with schizophrenia or schizoaffective disorder from the Afrikaner founder population in South Africa who are considered comparable to Caucasian patients from the United States. A comprehensive data capturing sheet was completed. RESULTS : When schizophrenia and schizoaffective disorder diagnoses were considered jointly, we found no significant differences between the sporadic and the familial groups for age at disease onset, season of birth, comorbid diagnoses, clinical symptomatology, history of suicide or marital status. When the diagnoses were examined separately, however, the sporadic schizoaffective disorder, bipolar type, was found to have a significantly lower age at onset (mean 20.6 vs. 25.3 years). CONCLUSION : The sporadic schizoaffective disorder, bipolar type, forms a more homogeneous subgroup for genetic studies.The National Institute for Mental Health (grant number R01MH61399 to M.K.) and the National Research Foundation (grant number IFR160224159056 to J.L.R).http://www.sajp.org.za/index.php/sajphj2020PsychiatryStatistic

Advancing paternal age at birth is associated with poorer social functioning earlier and later in life of schizophrenia patients in a founder population

Consistent associations have been found between advanced paternal age and an increased risk of psychiatric disorders, such as schizophrenia in their offspring. This increase appears to be linear as paternal age increases. The present study investigates the relationship between early deviant behaviour in the first 10 years of life of patients as well as longer term functional outcome and paternal age in sporadic Afrikaner founder population cases of schizophrenia. This might improve our understanding of Paternal Age-Related Schizophrenia (PARS). Follow up psychiatric diagnosis was confirmed by the Diagnostic Interview for Genetic Studies (DIGS). An early deviant childhood behaviour semi-structured questionnaire and the Specific Level of Functioning Assessment (SLOF) were completed. From the logistic regression models fitted, a significant negative relationship was found between paternal age at birth and social dysfunction as early deviant behaviour.Additionally, regression analysis revealed a significant negative relationship between paternal age at birth and the SLOF for interpersonal relationships later in life. Early social dysfunction may represent a phenotypic trait for PARS. Further research is required to understand the relationship between early social dysfunction and deficits in interpersonal relationships later in life.http://www.elsevier.com/locate/psychres2017-09-30hb2016PsychiatryStatistic