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Biomedical subjects

G Lewis

Publications and source records attributed to G Lewis.

At least 145 records · Page 8Linked to original sources
PubMed1997

IQ and risk for schizophrenia: a population-based cohort study.

BACKGROUND: This study aimed to quantify the association between low IQ and the later development of psychosis in a population-based cohort study of 18-year-old conscripts. METHODS: Fifty thousand males conscripted into the Swedish army in 1969-1970 were followed by means of the Swedish National Register of Psychiatric Care up to 1983. Tests of verbal and visuospatial abilities, general and mechanical knowledge and several psychosocial variables were recorded at conscription. RESULTS: One hundred and ninety-five subjects were admitted to hospital with schizophrenia and 192 with a non-schizophrenic psychosis on ICD-8 criteria. The distribution of scores in those later diagnosed as suffering from schizophrenia was shifted in a downward direction, with a linear relationship between low IQ and risk. This remained after adjustment for potential confounders. The risk for non-schizophrenic disorders was also higher in those with lower IQ but the effect was less marked and non-linear. Only poorer performance on the verbal tasks and mechanical knowledge test conferred a significantly increased risk for schizophrenia after taking into account general intellectual ability. Low IQ at conscription was not related to age of onset. CONCLUSIONS: The results confirm the importance of low intellectual ability as a risk factor for schizophrenia and other psychoses. This is unlikely to be due to prodromal decline or known confounders. The association could be directly causal with cognitive impairment leading to false beliefs and perceptions, or could be indirect with any factors causing lower IQ, such as abnormal brain development increasing the risk for schizophrenia.

Adolescent↗
PubMed1997

X-ray structure of 5-aminolaevulinate dehydratase, a hybrid aldolase.

5-Aminolaevulinate dehydratase (ALAD) is a homo-octameric metallo-enzyme that catalyses the formation of porphobilinogen from 5-aminolaevulinic acid. The structure of the yeast enzyme has been solved to 2.3 A resolution, revealing that each subunit adopts a TIM barrel fold with a 39 residue N-terminal arm. Pairs of monomers wrap their arms around each other to form compact dimers and these associate to form a 422 symmetric octamer. All eight active sites are on the surface of the octamer and possess two lysine residues (210 and 263), one of which, Lys 263, forms a Schiff base link to the substrate. The two lysine side chains are close to two zinc binding sites one of which is formed by three cysteine residues (133, 135 and 143) while the other involves Cys 234 and His 142. ALAD has features at its active site that are common to both metallo- and Schiff base-aldolases and therefore represents an intriguing combination of both classes of enzyme. Lead ions, which inhibit ALAD potently, replace the zinc bound to the enzyme's unique triple-cysteine site.

Amino Acid Sequence↗
PubMed1997

The Shona Symptom Questionnaire: the development of an indigenous measure of common mental disorders in Harare.

The objective of this study was to develop an indigenous measure of common mental disorders (CMD) in the Shona language in Zimbabwe. Ethnographic and qualitative studies elicited idioms of distress of mental disorder leading to the preliminary Shona Symptom Questionnaire (SSQ), and items from the Self-Report Questionnaire (SRQ) were added to it. The 56-item Preliminary Shona Symptom Questionnaire (PSSQ) was administered to 302 randomly selected primary care attenders, of whom 100 were classified as cases on the basis of agreement between care provider assessment and a psychiatric interview. Discriminant analysis identified 14 items that were the strongest predictors of mental disorder. The 14-item SSQ has a high level of internal consistency (Cronbach's alpha = 0.85). The items are a mixture of emic and etic phenomena. The total score correlates strongly with patients' self-assessment of the emotional nature of their illness. Satisfactory specificity and sensitivity occurred at a cut-off point of 7/8. The SSQ is the first indigenous measure of mental disorder developed in sub-Saharan Africa to have included idioms or distress of primary care attenders and involved patients consulting traditional medical practitioners. It promises to be a useful instrument for epidemiological and clinical research. The methodology used is an innovative way of combining etic and emic methods in the evaluation of CMD.

Adolescent↗
PubMed1997

Strategies for the prevention of psychiatric disorder in primary care in south London.

STUDY OBJECTIVE: To compare the potential impact of high risk and population based approaches to the prevention of psychiatric disorder, using a representative sample of general practice attenders as the target population. DESIGN: This was a prospective cohort study. SETTING: A health centre in south London. PARTICIPANTS: Three hundred and seven consecutive attenders aged 16-65, recruited at randomly selected general practice surgeries. MAIN RESULTS: A linear association was found between the number of different types of socioeconomic adversity reported at recruitment (T1) and the prevalence of psychiatric disorder one year later (T2). The population attributable fraction (PAF) for socioeconomic adversity at T1 was 37.4%. In theory, social interventions for high risk individuals at T1 would reduce the prevalence of psychiatric disorder at T2 by 9% at most, compared with a reduction of 18% if just one item of socioeconomic adversity were eliminated among those with any socioeconomic risk factors. CONCLUSIONS: Social interventions targeted at individuals at highest risk of the most common mental disorders are likely to be extremely limited in their capacity to reduce the prevalence of these conditions. A population based risk reduction strategy, modified according to individual risk, represents a potentially feasible and effective alternative.

Adolescent↗
PubMed1997

Putting trials on trial--the costs and consequences of small trials in depression: a systematic review of methodology.

STUDY OBJECTIVE: To determine why, despite 122 randomised controlled trials, there is no consensus about whether the selective serotonin reuptake inhibitors or tricyclic and related antidepressants should be used as first line treatment of depression. DESIGN: Systematic review of all RCTs comparing selective serotonin reuptake inhibitors and tricyclic or heterocyclic antidepressants. MAIN RESULTS: The shortcomings identified in the 122 trials were as follows: (1) there was inadequate description of randomisation, (2) the outcomes used were mainly observer rated measurements of depression, and studies failed to use quality of life measures or perform economic evaluations, (3) doses of tricyclic antidepressants were inadequate, (4) generalisability of studies was poor (including a reliance on secondary care settings and inadequate follow up), and (5) there were statistical shortcomings such as low statistical power, failure to use intention to treat analyses, and the tendency to make multiple comparisons. CONCLUSIONS: Future RCTs should be designed to inform policy makers and address these methodological shortcomings.

Antidepressive Agents, Tricyclic↗
PubMed1997

The severity of coronary atherosclerosis in type 2 diabetes mellitus is related to the number of circulating triglyceride-rich lipoprotein particles.

The presence or absence of coronary artery disease (CAD) in diabetic patients has been related to the level of circulating plasma lipoproteins. This study examines whether there is a relationship between the actual severity of CAD and the plasma concentration of major classes of plasma lipoproteins (HDL, LDL, triglyceride-rich lipoproteins (TRL), and their Sf 12 to 60 and Sf 60 to 400 subfractions), particularly the numbers of lipoprotein particles, in men and women with type 2 diabetes. 174 diabetic patients (136 men, 38 women) who underwent angiography were studied. Nine specific coronary segments were scored. The population was divided into tertiles according to the angiographic severity of their coronary disease: mild CAD: coronary score 1 to 10; moderate CAD: coronary score 11 to 13; or severe CAD: coronary score 14 to 22. The main findings were that the numbers of particles (as reflected by the apoB levels) of the TRL were greater in those with moderate and severe disease than in those with mild disease (P = .001). There was a significant correlation between the coronary score and the apoB in TRL (P = .006). There were parallel but nonsignificant changes in triglyceride levels. ApoA-I was lower in patients with moderate and severe disease (P = .01). These differences were more striking in women than they were in men. There were no differences in plasma, LDL, or HDL cholesterol or in LDL apoB or Lp(a). Multiple linear regression analysis, when adjusted for sex, age, and BMI, showed that three lipid variables (TRL apoB, LDL cholesterol, and plasma apoA-I) significantly and independently predicted the coronary score. This study demonstrates that in type 2 diabetes, the severity of angiographically evaluated CAD is positively related to the numbers of TRL particles in the plasma. This relationship is stronger in women than in men, and it is independent of HDL and LDL.

Adult↗
PubMed1997

Discontinuation rates of SSRIs and tricyclic antidepressants: a meta-analysis and investigation of heterogeneity.

BACKGROUND: Previous meta-analyses suggest that individuals treated with serotonin-specific reuptake inhibitors (SSRIs) in randomised controlled trials (RCTs) are less likely to discontinue treatment than those on tricyclic antidepressants. This metaanalysis investigates whether this is due to the frequent use in RCTs of older reference tricyclics (imipramine and amitriptyline), which may have worse side-effects than more recent compounds. METHODS: A meta-analysis of RCTs comparing tricyclic and heterocyclic antidepressants with SSRIs in the treatment of depression. RESULTS: The overall odds ratio of discontinuation on tricyclic/heterocyclic antidepressants compared with SSRIs was 0.86 (95% CI 0.78-0.94). The odds ratio for reference tricyclics was 0.82 95% CI 0.72-0.23), newer tricyclics 0.89 (95% CI 0.74-1.06), and heterocyclics 1.02 (95% CI 0.78-1.35). The pooled advantage of SSRIs over tricyclics was maintained whether the population studied consisted of younger adults or only the elderly. No differences in discontinuation rates were detected between the SSRIs. CONCLUSIONS: The lower rate of discontinuation in patients on SSRIs may be due to the use of old tricyclics (which have worse side-effects) as reference compounds. The SSRIs do not show a statistically significant difference in discontinuation rates when compared with newer tricyclics or heterocyclics.

Antidepressive Agents, Tricyclic↗
PubMed1997

Mechanical evaluation of humeral interlocking intramedullary nails.

Implantation of an interlocking intramedullary nail has rapidly become the modality of choice for the management of various fractures of the humeral shaft; namely, those that are not minimally displaced, impacted and/or stable. The mechanical properties of the nail per se or the nail-bone construct are essential to the nail's satisfactory clinical performance. The present work is a critical review of this topic, using reports given in the opne literature. Whence, gaps and unresolved controversies in the current knowledge base are identified. Expositions on future work, based on the foregoing observations as well as uncharted topics, are presented.

Adult↗
PubMed1997

Effect of the archwire slot profile on the performance of bonded orthodontic brackets.

The finite element analysis method and a two-dimensional idealization were used to conduct a parametric study of the effect of the archwire slot (or insert) profile on the stresses in, deformation of, and efficiency of a model of a bonded edge-wise "combination-materials" type of orthodontic bracket. The results are consistent with a priori expectations and are qualitatively the same as those obtained by previous workers who used the two-dimensional photoelasticity stress analysis method. The results thus highlight a possible approach to improving the clinical performance of these brackets.

Computer Simulation↗
PubMed1997

Strategies for preventing suicide.

BACKGROUND: The Health of the Nation includes a target for reducing population suicide rates. We have examined and quantified various high-risk and population-based strategies for prevention based upon a number of stated assumptions and hypothetical interventions. METHOD: The published literature was used to estimate the population attributable fractions for both high-risk and population-based strategies. The number needed to treat for the high-risk strategies was calculated, assuming an intervention that reduced suicide rates by 25%. RESULTS: Interventions that would reduce rates of suicide by 25% would reduce population rates by about 2.6% for those recently discharged from hospital and by up to 5.8% for those presenting to general hospital with deliberate self-harm. The population attributable fraction for unemployment was 10.9%. CONCLUSIONS: High-risk strategies will have only a modest effect on population suicide rates, even if effective interventions are developed. Evaluating interventions for deliberate self-harm patients seems worthwhile. The UK Government's target for suicide reduction is more likely to be achieved using population-based strategies. Reducing the availability of methods commonly used for committing suicide is the most practicable current policy, although more radical approaches, for example reducing unemployment, may also substantially reduce suicide rates.

Analgesics↗
PubMed1997

Modeling the tensile behavior of human Achilles tendon.

Uniaxial quasi-static tensile stress, sigma versus strain, epsilon, data were obtained from 29 cadaveric Achilles tendons (donor ages: 36 to 100 years), at a strain rate of either 10 or 100%/s. These results were then used in modeling the elastic component of the tensile deformational behavior of this tissue. Two approaches were taken. In the first, it was shown that the following constitutive relation provided an excellent fit to the elastic section of the sigma-epsilon curve, sigma = C epsilon exp[D epsilon + F epsilon 2], with C, D and F being material constants, whose values for the present dataset were found to be C = 2.00 +/- 0.99, D = 0.089 +/- 0.087 and F = -0.0047 +/- 0.0095. The values of these coefficients were not statistically significantly affected by either donor age or test strain rate. In the second approach, the value of the modulus of elasticity of a filamentary polymer matrix composite material was computed as a function of various combinations of values of the modulus of elasticity of the fiber, the modulus of elasticity of the matrix, and angle of orientation of the principal material axes with respect to the reference coordinate axes (theta) for a fiber volume fraction of 0.6 and a material Poisson's ratio of 0.4. By comparing these results with the experimentally-obtained values of the tangent modulus of elasticity of the tendons (defined as the slope of the linear section of the post-toe zone in the sigma-epsilon plot), and assuming that the tendon may be idealized as a filamentary polymer matrix composite material, the suggestion is made that the winding angle of the fibers (collagen fibrils) in the tendon (taken to be equal to theta) is about 6 degrees.

Achilles Tendon↗
PubMed1997

Evaluation of tibial interlocking intramedullary nails.

Interlocking intramedullary nailing is currently the leading method of treating a wide assortment of tibial fractures. Satisfactory clinical performance of such a nail is interwoven with the mechanical characteristics (chiefly, static strength, fatigue strength, fatigue life and stiffness) of the nail-contiguous fractured bone construct. The present work reviews the open literature on these nails and the mechanical performance of the constructs. Based on the observations made in the review, areas for future work are identified and expounded upon.

Bone Nails↗
PubMed1996

Psychiatric and alcohol disorders as risk factors for drug abuse. A case-control study among adults in Rio de Janeiro, Brazil.

This study tested the hypothesis that a history of psychiatric and alcohol disorders would affect the risk of developing drug abuse or dependence later in life. This case-control study selected cases and controls using the "snowball" technique in order to obtain cases from this "hidden" population and to match sex, age and friendship. Information was gathered using the Composite International Diagnostic Interview (CIDI), and computer diagnoses were generated according to the DSM-III-R criteria. The study included 370 subjects. Results of the conditional logistic regression analysis showed that having a history of alcohol dependence was independently associated with an increased risk of drug abuse/dependence (OR = 2.6, 95% CI 1.1-6.0) and that this risk was even higher for those whose alcohol dependence occurred in combination with another psychiatric disorder (OR = 4.6, 95% CI 2.1-10.0). An increased risk of drug abuse/dependence was also found for those who were aged 12 years or under when their first psychiatric disorder was manifested (OR = 2.2, 95% CI 1.3-3.7) and among those with two or more psychiatric disorders (OR = 2.5, 95% CI 1.5-4.1). These findings suggest that programmes directed towards the treatment and prevention of drug abuse must be prepared to address psychiatric and alcohol disorders in childhood and adolescence.

Adolescent↗
PubMed1996

Age-period-cohort analysis of the incidence of schizophrenia in Scotland.

Studies examining a possible decline in the incidence of schizophrenia over the last two to three decades have paid little attention to the possible role of birth cohort effects. We collected data on a Scottish national sample of all schizophrenic patients, admitted for the first time between 1966 and 1990 (N = 11348; male = 6301). In an Age-Period-Cohort analysis, a full model, incorporating three factors, had a substantially better fit to the data than other models (especially, an Age-Period model), providing clear evidence of the presence of a cohort effect. After adjustment for the effects of age and period, there was a 55% reduction in the rate of schizophrenia in men and a 39% fall in the number of women over the 50-year birth period from 1923 to 1973. The marked decline in the first admission rates observed in Scotland cannot, however, be attributed entirely to this cohort effect. Rather, a greater proportion of the declining first admission rates (88%) is ascribed to the period effect (i.e. artefactual or causally related cross-sectional effects). Nevertheless, the fact that a birth-cohort effect accounts for part of the declining incidence, suggests that causal environmental factors operating early in life have been diminishing in intensity.

Adolescent↗
PubMed1996

A longitudinal study of factors predicting change in cognitive test scores over time, in an older hypertensive population.

This study aims to describe factors associated with cognitive decline among 2584 subjects, aged 65-74, who were followed up for 54 months in the Medical Research Council Elderly Hypertension Trial (1982-1989). The subjects completed a cognitive test, the Paired Associate Learning Test (PALT), five times over this period. Decline on the PALT was associated with advanced age, male sex, rural residence, depression and low intelligence. These effects were modified by gender and level of pre-morbid intelligence. Advanced age, rural residence and number of cigarettes smoked daily were only associated with PALT decline among women of below median intelligence. The association between depression and PALT decline was only apparent in women of below median intelligence and men of above median intelligence. While these findings are consistent with other research into cognitive decline, they differ in some ways from reported risk factors for dementia, suggesting aetiological separateness. That women were more vulnerable than men to the effects of age and smoking raises the question of the impact on cognition of accelerated atherosclerosis after the menopause.

Aged↗