Unequal access and unmet need: neurotic disorders and the use of primary care services

BACKGROUND

In this paper we use data from the National Survey of Psychiatric Morbidity to examine how many people with neurotic disorders receive professional evaluation, and how this is affected by clinical and sociodemographic differences. We hypothesized that psychiatric symptoms and attendant dysfunctions would both have an effect on contacting, and that key demographic variables would not.

METHOD

The household component of the British National Surveys of Psychiatric Morbidity was based on a random sample of > 10,000 subjects. Psychiatric symptoms and ICD-10 diagnosis were established by lay interviewers using the CIS-R. Social dysfunction was tapped by asking about difficulties in performing seven types of everyday activity. We examined symptom score, ADL deficit score and demographic variables in relation to contact with primary care physicians for psychiatric symptoms.

RESULTS

The major determinant of contacting a primary care physician was severity, mainly due to the level of psychiatric symptoms, but with an independent contribution from social dysfunction. There were also significant contributions from sex, marital status, age, employment status and whether the subject had a physical condition as well.

CONCLUSIONS

The major influence on whether people seek the help of their family doctors for mental health problems is the severity of disorder. Although there are some social inequalities in access to family doctors, these are less important. The most salient finding from our study is that even people suffering from high levels of psychiatric symptoms very often do not have contact with professionals who might help them.

Relative roles of cement molecular weight and mixing method on the fatigue performance of acrylic bone cement: Simplex P versus Osteopal

The weight-average molecular weight (MW(w)) of a cement and the method used to mix its powder and liquid monomer constituents have been identified in the literature as key variables that affect mechanical properties of the fully polymerized cement that are relevant to its performance as a grouting agent in cemented arthroplasties. The goal of the present work was to identify which of these two variables exerts the greater effect in the case of fully reversed tension-compression fatigue performance. A judicious choice of cement brands, Surgical Simplex P and Osteopal, and the use of hand versus vacuum mixing, permitted this identification to be achieved. Three key observations were made in this work. First, for a given cement, the fatigue performance of vacuum-mixed specimens is far superior to that of hand-mixed ones, which may be a consequence of the substantially lower percentage areal porosity of the former specimens. Second, regardless of the mixing method, the fatigue performance of Osteopal outstrips that of Simplex P, a result that is attributed to the much higher MW(w) of the former cement. Third, hand-mixed Osteopal outperforms vacuum-mixed Simplex P (especially at low alternating stress levels), indicating that MW(w) of a bone cement is more influential than mixing method on its fatigue performance.

Clarifying the relationship between unexplained chronic fatigue and psychiatric morbidity: results from a community survey in Great Britain

OBJECTIVE

The study examined the associations between several sociodemographic and psychosocial variables and unexplained chronic fatigue in the community before and after adjustment for psychiatric morbidity and determined the prevalence of fatigue and rate of disability resulting from fatigue in the general population.

METHOD

The study is a secondary analysis of 1993 data from a household survey of psychiatric morbidity conducted by the Office for Population Censuses and Surveys in Great Britain. The survey included 12,730 subjects age 16-64 years. Unexplained chronic fatigue was used as the dependent variable in a logistic regression analysis, with various sociodemographic and psychosocial variables and psychiatric morbidity as the independent variables. Psychiatric morbidity was assessed by using the Revised Clinical Interview Schedule. Fatigue was measured by using the fatigue section of the Revised Clinical Interview Schedule.

RESULTS

A total of 10,108 subjects agreed to cooperate (79.4% participation rate). The prevalence of unexplained chronic fatigue was 9%. Subjects with psychiatric morbidity had higher rates of fatigue. Adjustment for psychiatric morbidity had a minor effect on the associations between sociodemographic factors and chronic fatigue. After adjustment, older subjects, women, and couples with children had higher rates of fatigue. Single subjects, widowed subjects, adults living with parents, and economically inactive subjects had lower rates of fatigue. Fatigue was associated with considerable disability, but most of this disability was explained by the association between fatigue and psychiatric morbidity.

CONCLUSIONS

Unexplained chronic fatigue is a common condition, strongly associated with psychiatric morbidity. The close relationship between fatigue and psychiatric morbidity should not obscure the possibility of differences as well as similarities in their etiologies.

Dynamic thermomechanical properties and crystallinity of ultrahigh molecular weight polyethylene tibial inserts

A dynamic thermomechanical analysis method was used to determine the values of the viscoelastic parameters, storage modulus (E') and the tangent of the loss angle (tan delta) of samples taken from the near surface and core regions of ultrahigh molecular weight polyethylene (UHMWPE) bar stock specimens that had been aged in ambient laboratory air for 12 months (the control group) and UHMWPE tibial inserts that had been subjected to the following treatments: gamma sterilization followed by shelf aging in ambient laboratory air for between 56 and 112 months or ethylene oxide (EtO) gas sterilization followed by shelf aging in ambient laboratory air for 73 months. Differential scanning calorimetry was used to determine the melt temperature and percentage crystallinity (%C) of these samples. There were three main findings. First, EtO sterilization produced no statistically significant effect on the values of E' or tan delta (relative to those for the control group), but the values of these parameters were markedly affected by gamma sterilization. Second, for gamma-irradiated samples, E' increased with an increase in the shelf aging time. Third, there was a strong direct association between E' and % C. The various potential uses of this association are described, paying special attention to its likely role in predicting the in vivo wear of UHMWPE tibial inserts.

Effect of mixing method and storage temperature of cement constituents on the fatigue and porosity of acrylic bone cement

The influence of the storage temperature of the cement constituents prior to mixing (21 vs. 4 degrees C) and the mixing method (hand mixing vs. vacuum mixing) on the uniaxial tension-compression fatigue performance and porosity of Palacos R acrylic bone cement was studied. The fatigue results were analyzed using the three-parameter Weibull equation. The fatigue performance was expressed as an index I, which was defined as the product of the Weibull characteristic fatigue life and the square root of the Weibull slope. Statistical analyses of these results show that although the mixing method (for a given storage temperature) exerts a significant influence on the fatigue performance and areal porosity, the effect of storage temperature (for a given mixing method) on either of these parameters is not significant.

Properties of acrylic bone cement: state of the art review

Acrylic bone cement occupies a distinctive place in the hierarchy of synthetic biomaterials, because it is the only material currently used for anchoring the prosthesis to the contiguous bone in a cemented arthroplasty. However, the cement is not without its drawbacks. The main one is the role that it has been postulated to play in the aseptic loosening and, hence, clinical life of the arthroplasty. In turn, this role is directly related to the mechanical properties of the cement, especially the resistance to fracture of the cement in the mantle at the cement-prosthesis interface or the cement-bone interface. The present work is a detailed critical review of the recent literature on the properties of bone cement that are considered germane to its use in the stated application. The relevant properties are identified and a case is made for including each of them. Compilations of the values of these properties, obtained under clearly identified conditions, are presented for the six commercial formulations of bone cement in current popular orthopedic use. The gaps and unresolved questions in the current data base, efforts that should be made to address these issues, and research directions are covered.

Effect of mixing method on selected properties of acrylic bone cement

The present study was an investigation of the effect of the method of mixing the constituents of CMW3 bone cement on selected physical and mechanical properties of the fully polymerized cement. Five such methods were used: hand mixing; "active" vacuum mixing; mixing in a machine that allowed simultaneous mechanical mixing and centrifugation; mixing using this machine followed by application of a "passive" vacuum; and application of a passive vacuum followed by mixing in the machine. It was found that the best overall results were obtained from cement that had been mixed using the second and fifth methods and the values of the properties were: density, 1220 to 1246 kg/m3; areal porosity, 0.02 to 7.04%; ultimate compressive strength, 84 to 112 MPa; ultimate compressive strain, 5.1 to 6.4%; and compressive modulus of elasticity, 2249 to 2877 MPa.

Polyethylene wear in total hip and knee arthroplasties

The role that ultrahigh molecular weight polyethylene (UHMWPE) wear at bearing surfaces in total hip and knee arthroplasties plays in the clinical life of these implants cannot be overemphasized. This subject has therefore been attracting enormous research attention on both fundamental and technological levels. Given this, it is important to detail the main features of the knowledge base and describe research directions that may culminate in the production of new and/or improved varieties of UHMWPE material and components. These aspects are the subject of the present review.

A new method of determining the J-integral fracture toughness of very tough polymers: application to ultra high molecular weight polyethylene

The thrust of the present work was the development of a new modification to the ASTM E813-89 method for determining the J-integral fracture toughness, JIc, of ductile polymers. The advantages and limitations of the modification, vis a vis the ASTM E813-89 and the hysteresis methods, are presented. The modification was then applied to investigate the effect of sterilization method on the JIc of ultra-high-molecular-weight polyethylene (UHMWPE) specimens that were subsequently aged (heated, in a cylindrical pressure vessel, in oxygen gas at 507 kPa and 70 degrees C for 14 d). Relative to the unsterilized material, it was found that gamma-irradiating the polymer leads to a significant drop in its JIc, while sterilization using either ethylene oxide or gas plasma produced no effect on its JIc. The clinical implications of the present results for the in vivo performance of UHMWPE counterfaces, and, hence, hip and knee arthroplasties, are fully discussed.

Psychiatric disorder and dysfunction in the UK National Survey of Psychiatric Morbidity

BACKGROUND

Psychiatric symptoms are wide-spread in the general population, but have little effect on performance. Deficits in performance and psychiatric symptoms may be the end point of processes common to both, or they may be caused by quite different factors. In this paper we examine the epidemiological distribution of psychiatric symptoms and performance deficits, as indicated by difficulties in activities of daily living (ADL). We hypothesised that ADL difficulties are partly independent of psychiatric symptoms, and that this is reflected in a different demographic distribution.

METHOD

The household component of the National Surveys of Psychiatric Morbidity was based on a sample of around ten thousand subjects selected at random from the population of Great Britain. Psychiatric symptoms were elicited by lay interviewers using the revised Clinical Interview Schedule. Performance was assessed by asking about difficulties experienced in performing seven types of everyday activity. In this paper, our chosen variables were overall symptom and ADL deficit scores, and these were related to standard demographic variables.

RESULTS

There were significant differences in the epidemiological distribution of psychiatric symptoms and ADL difficulties. In particular, men experienced more ADL difficulties at a given symptom level than women. There were also differences in relation to social class, employment status, marital status, ethnic group and age.

CONCLUSIONS

ADL deficits and psychiatric symptoms are related in the general population, and this probably represents common factors in their origin. However, discrepancies in the social distribution of these phenomena suggest there are also aetiological differences. These do not appear to be the result of the impact of physical illness on activities of daily living. Our results emphasise that ADL difficulties should be studied separately, particularly in investigations of treatment seeking.

Correlation between impact strength and fracture toughness of PMMA-based bone cements

The thrust of the work involved determining the impact strength, IS (in kJ m(-2)) [using non-ASTM-sized Charpy-type specimens and an in-house impact tester] and fracture toughness, K1c (in MPa square root(m)) [using ASTM-sized rectangular compact tension specimens] of Surgical Simplex P and three variants of Palacos R acrylic bone cements. The attractions and drawbacks of this method for determining IS are detailed. The best fit to the K1c and IS results yielded a power relationship K1c = 0.795(IS)(0.59). The usefulness and limitations of this relationship are detailed.

Effect of two variables on the fatigue performance of acrylic bone cement: mixing method and viscosity

The goal of the present work was to establish the relative influence of one exogenous variable versus one endogenous variable on the fully-reversed tension-compression fatigue performance of bone cement. The method used to mix the cement constituents was the exogenous variable, while the viscosity of the mixed cement dough was the endogenous variable. Two commercial cement formulations (Palacos R and Osteopal) and two cement mixing methods (hand mixing and vacuum mixing) were used. It was found that for a given mixing method, cement viscosity exerts a marginal influence on fatigue performance. On the other hand, for a given cement formulation, vacuum mixing led to a statistically significant improvement in fatigue performance. The present results demonstrate the superior influence of mixing method over cement viscosity.

Selective serotonin reuptake inhibitors versus tricyclic and heterocyclic antidepressants: comparison of drug adherence

BACKGROUND

Selective serotonin reuptake inhibitors are thought to have better discontinuation rates (i.e. less people dropping out) than tricyclic and heterocyclic antidepressant drugs. It is important to quantify the drop-out rates of different antidepressant drugs in order to have a better understanding of the relative tolerability of these drugs.

OBJECTIVES

To assess the comparative tolerability of selective serotonin reuptake inhibitors and tricyclic/heterocyclic antidepressant drugs.

SEARCH STRATEGY

We searched the Cochrane Collaboration Depression, Anxiety and Neurosis Controlled Trials Registers (1997 to 1999), MEDLINE (1966 to 1999), EMBASE (1974 to 1999) We also searched specialist journals, the reference lists of relevant papers and previous systematic reviews, conference abstracts and government documents. Representatives of the pharmaceutical industry were contacted.

SELECTION CRITERIA

Parallel group randomised controlled trials comparing selective serotonin reuptake inhibitors with tricyclic or heterocyclic antidepressants in people with depression.

DATA COLLECTION AND ANALYSIS

Two reviewers independently extracted data and a third reviewer checked any cases of disagreement.

MAIN RESULTS

We included 136 trials. The selective serotonin reuptake inhibitors showed less participants dropping out compared to the tricyclic/heterocyclic group (odds ratio 1.21, 95% confidence interval 1.12 to 1.30). A statistically significant difference was found in total drop-outs between the selective serotonin reuptake inhibitors and the old tricyclics as well as the newer tricyclics. When the selective serotonin reuptake inhibitors were compared to the heterocyclic antidepressants, there was a non significant difference favouring the selective serotonin reuptake inhibitors. The poor tolerability profile of the old tricyclics was explained by differences in drop-outs for side-effects, but not for inefficacy.

REVIEWER'S CONCLUSIONS

Whilst selective serotonin reuptake inhibitors do appear to show an advantage over tricyclic drugs in terms of total drop-outs, this advantage is relatively modest. This has implications for pharmaco-economic models, some of which may have overestimated the difference of drop-out rates between selective serotonin reuptake inhibitors and tricyclic antdepressants. These results are based on short-term randomised controlled trials, and may not generalise into clinical practice.

Heritability of social cognitive skills in children and adolescents

BACKGROUND

Social cognitive skills are those which enable understanding of social situations; they are relevant to a variety of psychiatric disorders including autism, schizophrenia and externalizing behaviour problems in children.

AIMS

To examine the heritability of social cognitive skills.

METHOD

Using a population-based sample of twins aged 5-17, the genetic and environmental influences on social cognitive skills were examined.

RESULTS

Male scores were higher than female scores (P < 0.001), indicating poorer social cognition among males. A heritability of 0.68 (95% CI 0.43-0.78) was found, with shared environmental influences accounting for only 0.05 of the variance (95% CI 0.00-0.28). This could be removed from the model without worsening the fit. There were no significant differences in genetic effects between the genders, but age-related changes were found, with younger twins showing greater genetic influence on social cognition.

CONCLUSIONS

Social cognition appears to be under considerable genetic influence in the population and shows significant male-female differences. No gender differences in genetic influences on the variance of scores were found, but the effects of age were significant.

Mechanisms of photoreceptor death and survival in mammalian retina

The mammalian retina, like the rest of the central nervous system, is highly stable and can maintain its structure and function for the full life of the individual, in humans for many decades. Photoreceptor dystrophies are instances of retinal instability. Many are precipitated by genetic mutations and scores of photoreceptor-lethal mutations have now been identified at the codon level. This review explores the factors which make the photoreceptor more vulnerable to small mutations of its proteins than any other cell of the body, and more vulnerable to environmental factors than any other retinal neurone. These factors include the highly specialised structure and function of the photoreceptors, their high appetite for energy, their self-protective mechanisms and the architecture of their energy supply from the choroidal circulation. Particularly important are the properties of the choroidal circulation, especially its fast flow of near-arterial blood and its inability to autoregulate. Mechanisms which make the retina stable and unstable are then reviewed in three different models of retinal degeneration, retinal detachment, photoreceptor dystrophy and light damage. A two stage model of the genesis of photoreceptor dystrophies is proposed, comprising an initial "depletion" stage caused by genetic or environmental insult and a second "late" stage during which oxygen toxicity damages and eventually destroys any photoreceptors which survive the initial depletion. It is a feature of the model that the second "late" stage of retinal dystrophies is driven by oxygen toxicity. The implications of these ideas for therapy of retinal dystrophies are discussed.