Factors of psychological distress: clinical value, measurement substance, and methodological artefacts.

PURPOSE: Psychometric models and statistical techniques are cornerstones of research into latent structures of specific psychopathology and general mental health. We discuss "pivot points" for future research efforts from a psychometric epidemiology perspective, emphasising sampling and selection processes of both indicators that guide data collection as well as samples that are confronted with them. METHOD: First, we discuss how a theoretical model of psychopathology determines which empirical indicators (questions, diagnoses, etc.) and modelling methods are appropriate to test its implications. Second, we deal with how different research designs introduce different (co-)variances between indicators, potentially leading to a different understanding of latent structures. Third, we discuss widening the range of statistical models available within the "psychometrics class": the inclusion of categorical approaches can help to enlighten the debate on the structure of psychopathology and agreement on a minimal set of models might lead to greater convergence between studies. Fourth, we deal with aspects of methodology that introduce spurious (co-)variance in latent structure analysis (response styles, clustered data) and differential item functioning to gather more detailed information and to guard against over-generalisation of results, which renders assessments unfair. CONCLUSIONS: Building on established insights, future research efforts should be more explicit about their theoretical understanding of psychopathology and how the analysis of a given indicator-respondent set informs this theoretical model. A coherent treatment of theoretical assumptions, indicators, and samples holds the key to building a comprehensive account of the latent structures of different types of psychopathology and mental health in general.

Influence of dietary fat ingestion on asymmetrical dimethylarginine in lean and obese human subjects.

BACKGROUND AND AIMS: Asymmetrical dimethylarginine (ADMA) may contribute to hypertension and cardiovascular disease by decreasing NO formation. In diabetic patients, a high fat meal acutely increased plasma ADMA while impairing endothelial function. We hypothesized that chronic and acute increases in dietary fat intake augment ADMA also in lean and in obese subjects without diabetes. METHODS AND RESULTS: Seventeen lean and twelve obese volunteers were randomized to two weeks of isocaloric diets with approximately 20% or >40% calories from fat in a cross-over fashion. At the end of the high and low fat periods, volunteers received corresponding test meals. ADMA was measured by GC-MS/MS using a deuterated standard. Mean fasting plasma ADMA concentration was 0.52 (0.49-0.54; 95% CI) µmol/l in lean and 0.53 (0.50-0.55) µmol/l in obese subjects (p = 0.55). The two week high fat diet did not influence ADMA. Both test meals elicited a 6%increase in circulating ADMA in lean subjects. In obese subjects, plasma ADMA concentration did not change with the low fat meal, and decreased by approximately 4% with the high fat meal. CONCLUSION: Our findings challenge the idea that obesity and dietary fat intake have a major effect on plasma ADMA, at least in subjects without overt cardiovascular and metabolic disease. This finding is important with regard to dietary recommendations for weight loss. Overestimation of the influence of dietary fat intake and obesity on circulating ADMA in previous reports was most likely due to methodological issues concerning ADMA measurements.

How to determine whether conceptual endophenotypes can improve clinical outcomes in patients suffering from major depression: An exploratory approach.

Depression is a complex mental health disorder, resulting in a high degree of disability. Since symptom constellation, course, and outcome are heterogeneous in these patients, current research initiatives are striving to establish stratified diagnostic and treatment approaches. In the past two decades, Dirk Hellhammer and his team introduced Neuropattern, a new diagnostic concept, which is based on conceptual endophenotypes of the stress response network. We explore how to use this concept in clinical practice in order to ultimately determine whether it brings any value over standard care. In view of the novelty of the concept and the difficulties dealing with such a concept at a practical level, it was necessary to initiate an exploratory study to determine key factors for planning future clinical trials. We report results and knowledge gained from an exploratory single-site study investigating the use and potential benefits of Neuropattern in standard care. Inpatients (ICD-10 diagnosis F32, F33; Nö=ö178) were allocated to either treatment as usual (standard group, SG) or a novel Neuropattern oriented exploratory treatment (intervention group, IG). Symptom severity was assessed with psychometric tests at admission to hospital, during the first six weeks, and upon discharge from the hospital. In addition, direct and indirect costs were assessed for the 3-month-intervals prior to and after the hospital stay. Compared to the SG, depression scores of patients in the IG showed a faster decline once psychotherapeutic and pharmacological treatment were based on an individualized explanatory model. The patients in the IG with an F33 diagnosis showed a more pronounced reduction of depression severity during the stay in the hospital and a stronger and quicker reduction of general symptom severity. Comparing the average depression scores at the start of the study and after six weeks, symptom severity was reduced in all Neuropattern groups. Some limitations of the study have to be mentioned: The study was not blinded, was single-site, included highly depressed inpatients only, and was conducted for no longer than 8 months. The results highlight some important issues regarding taking the Neuropattern approach to the bedside and researching its efficacy and effectiveness to support personalized treatments in clinical care.

How is subjective well-being related to quality of life? Do we need two concepts and both measures?

Subjective well-being (SWB) and subjective quality of life (QoL) are key concepts describing experience, capacities, states, behaviours, appraisals, and emotional reactions to circumstances. Used widely in public discourse, policy, and research, their theoretical and empirical relations remain little explored. The present research aimed to develop an integrated model of SWB and QoL through empirically testing its overlapping and exclusive dimensions. Survey data was obtained from N = 2533 in 11 countries. Adults completed the WHOQOL Spirituality, Religion and Personal Beliefs (SRPB) instrument which assesses 33 QoL facets in 6 domains. The facets operationalize components of the hedonic SWB model, extended with eudaimonia, as SWB+. Network analyses, and regression models with random effect for cultural centre, assessed the differential contributions of SWB+ and QoL in predicting general QoL, explanatory power, and model parsimony. When all SWB+ and QoL variables are assessed together, the final model explains more variance in general QoL than either of the competing models; also it shows the most parsimonious fit. This fully integrated model contains only positive feelings from SWB+, with 13 other QoL facets drawn from all six domains, when adjusted for health status and educational level. These findings provide the foundation for a new Life Quality and Well-being (LQW) model that awaits confirmation. The LQW model improves on existing models of SWB+ and QoL by better explaining general QoL than facets of either model on its own. The 14 selected facets potentially offer a new, single measure with considerable conceptual breadth, and international foundations.

Variations in truncal body circumferences affect fat mass quantification with bioimpedance analysis.

OBJECTIVE: To test the hypothesis that variations in trunk circumferences influence the accuracy of bioimpedance analysis (BIA) for assessment of percent fat mass (%FM). SUBJECTS AND METHODS: %FM was predicted with BIA, and compared with air-displacement plethysmography (ADP) in a small sample of 35 overweight (OW), 21 normal weight and 8 underweight volunteers. Waist and hip circumferences were assessed, and 15 of the OW subjects were measured before and after weight reduction. RESULTS: BIA and ADP provided similar cross-sectional estimates of group mean %FM (28.9±10.0 and 31.3±13.0%, respectively). However, within individuals, there were large between-method differences (Diff(BIA-ADP)) ranging from -13 to +13 %FM. Furthermore, we found a systematic bias of BIA related to the degree of adiposity. Consequently, %FM and fat mass loss during weight reduction in OW were underestimated with BIA when compared with ADP. Waist and hip circumferences were inversely associated with resistance (R) and reactance (P<0.01), and with Diff(BIA-ADP) (P<0.001). In women, the variability in hip circumference explained 76%, and in men, the variability in waist circumference explained 59% of Diff(BIA-ADP). CONCLUSION: Resistance changes associated with variations in trunk circumferences decrease resistance, and therefore impair the accuracy of BIA to assess %FM.

Epigallocatechin-3-gallate and postprandial fat oxidation in overweight/obese male volunteers: a pilot study.

OBJECTIVES: Drinking green tea is associated with many health benefits, including increased fat oxidation. We tested the hypothesis that epigallocatechin-3-gallate (EGCG), the main green tea catechin, increases fat oxidation in obese men. METHODS: Ten healthy overweight/obese males (body mass index 31.3+/-0.8 kg/m(2)) were studied in a randomized, placebo-controlled, double-blind crossover trial. Study supplements were low EGCG (300 mg), high EGCG (600 mg), caffeine (200 mg), EGCG/caffeine (300 mg/200 mg) or placebo and were taken orally for 3 days. At the third day of supplementation, O(2) consumption and CO(2) production was measured by indirect calorimetry to assess energy expenditure and fat oxidation over 4 h each after overnight fasting and after a standardized test meal. RESULTS: Energy expenditure was not affected by any supplementation, neither after overnight fasting nor after the test meal. During the first 2 h after overnight fasting, fat oxidation increased by 7.7 (not significant, NS), 15.2 (NS), 26.3 (P<0.05 vs placebo) and 35.4% (P<0.01 vs placebo and low EGCG), for low EGCG, high EGCG, caffeine and EGCG/caffeine, respectively. During the first 2 h after the meal, the mean increase in fat oxidation was 33.3 (P<0.05 vs placebo), 20.2 (NS), 34.5 (P<0.05 vs placebo) and 49.4% (P<0.05 vs placebo) for low EGCG, high EGCG, caffeine and EGCG/caffeine, respectively. CONCLUSIONS: Low EGCG increases postprandial fat oxidation in obese men and this to the same extent as 200 mg caffeine, whereas high EGCG does not exert this effect. Fasting fat oxidation is increased only by caffeine (with or without EGCG). There is no synergism of low EGCG and 200 mg caffeine. Energy expenditure is not affected by EGCG.

Adipose tissue and circulating endothelial cell specific molecule-1 in human obesity.

Adipocytes produce the endothelial-cell specific molecule-1 (ESM-1), which inhibits leukocyte adhesion and migration through the endothelium. This study investigates ESM-1 expression and regulation in human adipose tissue. Subcutaneous abdominal adipose tissue was obtained from seventy postmenopausal women. Fourteen women subsequently underwent non-pharmacological weight reduction. In vitro experiments were performed on adipocytes isolated from human mammary adipose tissue. We determined gene expression by TaqMan RT-PCR and measured ESM-1 levels in serum and cell culture medium by ELISA. Mature adipocytes produced ESM-1. ESM-1 gene expression was higher in adipocytes than in preadipocytes. Cortisol inhibited ESM-1 gene expression in preadipocytes. Insulin and cortisol inhibited adipocyte ESM-1 production in adipocytes. This inhibitory effect of insulin was attenuated by insulin resistance, as ESM-1 gene expression in subcutaneous adipose tissue was increased in obese, hyperinsulinemic women. In contrast, ESM-1 serum levels were reduced in obese women and inversely correlated to C-reactive protein levels. Five percent weight loss did not markedly change gene expression. Circulating ESM-1 levels increased significantly, albeit modestly. ESM-1 is actively produced by adipocytes. However, since ESM-1 adipocyte gene expression and circulating plasma levels are not correlated, other sources of ESM-1 may be more important. Circulating ESM-1 levels are reduced in the overweight and obese, consistent with the notion that ESM-1 may play some role in obesity-associated vascular disease.

[A model of the isolated blood perfused lung of rats in testing hypoxic pulmonary vasoconstriction]. / Das Modell der isolierten blutperfundierten Lunge von Ratten zur Testung der hypoxischen pulmonalen Vasokonstriktion.

Comparing two variants of models (in situ, ex situ) of the isolated blood-perfused rat lung for measurement of the hypoxic pulmonary vasoconstriction the in situ preparation gave better results. The optimal severity of hypoxia was 2% O2 in intervals (hypoxia and normoxia, respectively) of seven minutes. The model works sufficiently for two hours.

Increase of the oxygenation and decrease of the intrapulmonary peak pressure at constant mean airway pressure using high-frequency jet ventilation in adult rabbits with lavage-induced severe respiratory distress syndrome compared to conventional mechanical ventilation.

Reports are contradictory about the value of high-frequency jet ventilation (HFJV) in the treatment of respiratory distress syndrome (RDS) [10, 11, 18 - 1, 2, 22, 25]. In a preliminary study on rabbits with healthy as well as surfactant deficient lungs, caused by lung lavage, at a constant mean airway pressure (MAP) and 20% inspiration time, the influence of the jet ventilation frequencies of 1, 3, 5, 10, 15 and 20 Hz (cycles per second) on the pressure oscillations along the airways as well as on blood gas and cardiac parameters were investigated. It was presumed that the breathing level, e.g. functional residual capacity plus 50% of the tidal volume is the same at constant MAP. The results during HFJV are compared to those of conventional mechanical ventilation (CMV). With increasing frequency the peak airway pressure (PAP) clearly decreased on both groups, while the self controlled positive end-expiratory pressure (AUTO-PEEP) increased. That means, the amplitude of the pressure oscillations became smaller and smaller, indicating that the danger of mechanical lesions might be reduced by this mode of ventilation. The arterial oxygenation (PaO2) increased with frequency. A threefold higher PaO2 could be obtained at 10 Hz in the animals with RDS lungs. The arterial carbon dioxide tension (PaCO2) increased nearly linear with the frequency in both groups. The inverse course of the arterial pH showed that it is possible to obtain at lower frequencies a respiratory alkalosis and at higher frequencies an acidosis. Optimal gas exchange could be obtained at about 10 Hz. Decreasing cardiac output with increasing frequency showed a good correlation to the pH in both groups. The effect was more influenced by the heart frequency than by the stroke volume especially in the RDS-group.

The influence of hypoxia and hyperoxia during metabolic acidosis and alkalosis on pulmonary haemodynamics.

In anaesthetised, mechanically ventilated Beagle dogs a moderate metabolic acidosis increased the pulmonary vascular resistance to a greater extent than moderate hypoxia. Alkalosis and hyperoxia did not alter the pulmonary vascular tone.