Das lineare Regressionsmodell von Aalen zur Analyse von Überlebenszeiten unter Berücksichtigung zeitveränderlicher Kovariablen

Data from clinical studies often contain time-dependent covariates, e.g. events like transplantation or an adverse drug reaction, or the changing measurements of laboratory data. The common approach uses only the covariate information at time t=0 for regression analyses, but this baseline analysis is not very satisfying. This paper applies the linear counting process by Aalen for failure time analysis, modified to deal with time-dependent covariates. In the main part we describe methods to estimate and visualize the cumulated regression function with respect to time-dependent covariates. After introducing a test for significance of the influence of covariates we display different methods to investigate model validity depending on martingale residuals, or by use of the Arjas plot. Coding and interpretation problems are shortly discussed. Results are illustrated with data from the Stanford Heart Transplantation Study and a study on Oropharynx carcinoma

Survivalanalysen mit Berücksichtigung der zeitlichen Kovariablenentwicklung in klinischen Studien

Data from the Stanford Heart Transplantation Study and our own study on brain tumor include time-dependent covariates like transplantation, which may switch only once, and others changing their value several times during follow-up. But classical analyses never used this additional information. In a comparative study we applied the time-dependent Cox model, pooled Cox regression and the linear counting process by Aalen to these data sets. All methods do show similar results when they are carried out in their 'fixed' version, i.e. using baseline information only, or when covariates are being treated as time-dependent. But the estimated effects do differ remarkably between fixed and time-dependent approaches, thus leading to different interpretations of risks

Fenofibrate Treatment Enhances Antioxidant Status and Attenuates Endothelial Dysfunction in Streptozotocin-Induced Diabetic Rats

Diabetic endothelial dysfunction is accompanied by increased oxidative stress and upregulated proinflammatory and inflammatory mediators in the vasculature. Activation of peroxisome proliferator-activated receptor-alpha (PPAR-α) results in antioxidant and anti-inflammatory effects. This study was designed to investigate the effect of fenofibrate, a PPAR-α activator, on the endothelial dysfunction, oxidative stress, and inflammation in streptozotocin diabetic rats. Diabetic rats received fenofibrate (150 mg kg−1 day−1) for 4 weeks. Fenofibrate treatment restored the impaired endothelium-dependent relaxation and increased basal nitric oxide availability in diabetic aorta, enhanced erythrocyte/liver superoxide dismutase and catalase levels, ameliorated the abnormal serum/aortic thiobarbituric acid reactive substances, and prevented the increased aortic myeloperoxidase without a significant change in serum total cholesterol and triglyceride levels. It did not affect the decreased total homocysteine level and the increased tumor necrosis factor-α level in the serum of diabetic rats. Fenofibrate-induced prevention of the endothelial function seems to be related to its potential antioxidant and antiinflammatory activity

Assessment the effect of diabetes education on self-care behaviors and glycemic control in the Turkey Nursing Diabetes Education Evaluating Project (TURNUDEP): a multi-center study

Background: Diabetes education in Turkey is provided by diabetes nurse educators in almost all healthcare organizations. However, the education is not standardized in terms of learning content, duration, and methods. This multi-center study was performed to assess the self-care behaviors and glycemic control following education provided to the patients with type 2 diabetes mellitus by diabetes nurse educators. Methods: This was a descriptive and cross-sectional study and included 1535 patients admitted to 28 public hospitals for the treatment of type 2 diabetes mellitus. The education was assessed by using a Patient Identification Form and Self-care Scale. Results: The proportion of individuals who received diabetes education within the last year was 78.5%, with 46.7% of them having received it once. Of the patients, 84.8% reported that they received diabetes education individually. It was found that the proportion of individuals who received education about oral antidiabetics (78.5%) and glucose testing at home (78.5%) was higher than the proportion of individuals who received education about exercise (58.8%) and foot care (61.6%). The status of diabetes education, education intervals, and the correlation of the education method with self-care and glycemic control was evaluated. Self-care and glycemic control levels were better among the patients who received diabetes education thrice or more and in patients who received education both individually and in a group (p < 0.05). Conclusions: Approximately three-quarters of individuals with type 2 diabetes mellitus received education by diabetes nurse educators in Turkey. Diabetes education is positively correlated with self-care and glycemic control levels among patients with type 2 diabetes mellitus. Efforts for generalization and standardized education for all diabetes patients are necessary. © 2022, The Author(s)

Time series analysis for the sulphur dioxide and particulate matter concentrations in the Aegean Region of Turkey

Air pollution has temporal and spatial variability. Time series analysis is commonly used to evolution of air pollutants in time. The sulphur dioxide (SO2) and particulate matter (PM10) concentrations in the cities of the Aegean Region for the period of 1990-2009 have been modelled by using autoregressive (AR) and autoregressive moving average (ARMA) models for the yearly, monthly, and winter season pattern. The AR(2) model was generally observed for the yearly SO2 data in the Aegean Region according to the all investigated and AR(p) models. The AR(1), AR(2) and ARMA(1,2) models could provide reliable and satisfactory predictions for the yearly PM10 data according to the all analysed models. The most suitable model was predominantly determined as ARMA(1,2) model according to the all investigated models, while the best fitted model was mainly determined as AR(1) model according to the AR(p) type models for the monthly SO2 and PM10 data. The AR and ARMA models could be used for reliable and satisfactory predictions for the winter season SO2 and PM10 data to all analysed models. Copyright © 2014 Inderscience Enterprises Ltd

Homocysteine levels of rats chronically treated with nicotine

Cigarette smoking has detrimental effects on the cardiovascular and cerebrovascular systems and among the contents of tobacco, nicotine shows considerable medical significance because of its toxicity. Homocysteine is an intermediate metabolite of methionine and increased levels of homocysteine may underlie atherosclerosis. In the present study, we investigated the relationship between the levels of homocysteine and nicotine in female and male rats which were treated with nicotine (0.35, 1.05 and 2.1 mg/kg, subcutaneously) for 20 days. Blood was obtained by cardiac puncture and serum cotinine levels, as an index of nicotine exposed, and homocysteine levels were measured by ;quot;Enzyme lmmunoassay (EIA);quot; and ;quot;Fluorescence Polarization lmmunoassay (FPIA);quot; respectively. Nicotine administration resulted in a dose dependent increase in the serum cotinine levels of the rats. Homocysteine levels were higher in female rats than male rats both in control and nicotine-administered groups, however nicotine treatment did not significantly change homocysteine levels in either sex. These results suggest that there is no direct correlation between plasma homocysteine levels and chronic nicotine exposure.Sigara içilmesi kardiyovasküler ve serebrovasküler sistemlerde zararlı etkilere neden olur ve toksisitesinden ötürü sigaradaki nikotin tıbben önemli bir bileşiktir. Homosistein, metioninin metabolizması sırasında oluşan bir ara üründür ve homosisteinin artışı aterosklerozun patogenezinde rol oynar. Bu çalışmada 20 gün boyunca nikotin (0.35, 1.05 ve 2.1 mg/kg, subkutan) uygulanan dişi ve erkek sıçanlarda nikotinin homosistein düzeylerine etkisi araştırılmıştır. Hayvanlardan intrakardiyak olarak kan alınmış ve serum homosistein düzeyleri immünolojik yöntem ("enzyme imunoassay", EIA) ile, maruz kalınan nikotin miktarının bir göstergesi olarak kotinin düzeyleri ise immünolojik floresans polarizasyon yöntemi ("fluorescence polarization immunoassay", FPIA) He ölçülmüştür. Sıçanlara nikotin uygulaması serum kotinin düzeylerinde doza bağımlı bir artışa neden olmuştur. Kontrol ve nikotin tedavi gruplarında dişi sıçanların homosistein düzeyleri erkek sıçanlardan yüksek bulunmuştur, ancak nikotin uygulaması her iki cinste de homosistein düzeylerinde anlamlı bir değişiklik yapmamıştır. Bu bulgular, kronik olarak nikotine maruz kalış He plazma homosistein düzeyleri arasında direkt bir ilişki olmadığını göstermektedir