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Statistical Adjustment (statistical + adjustment)
Selected AbstractsAlveolar bone loss associated with glucose tolerance in Japanese menDIABETIC MEDICINE, Issue 9 2003T. Marugame Abstract Aims Type 2 diabetes is known to affect alveolar bone loss (ABL). The purpose of this study was to examine whether impaired glucose tolerance (IGT) is associated with ABL, as is diabetes. Methods A case,control study was performed with 664 Japanese men aged 46,57 years. Panoramic radiographs revealed 513 severe ABL cases, 22 moderate ABL cases, and 129 controls with good alveolar bone. Diabetes status was classified into normal glucose tolerance (NGT), impaired fasting glucose (IFG), IGT, and newly diagnosed diabetes according to the fasting plasma glucose and 75-g oral glucose tolerance test (OGTT). Diabetes under treatment was excluded. Odds ratios (ORs) and 95% confidence intervals (CIs) were obtained from ordinal logistic regression analysis. Statistical adjustment was made for total cholesterol, HDL-cholesterol, triglyceride, rank in the Self Defence Forces (SDF), cigarette-years, alcohol use, body mass index, previous 10 years' brushing habits and instrument use other than toothbrush, and history of periodontal treatment. Results A significant, approximately three-fold increase in the crude OR (crude OR = 3.28; 95% CI = 1.16,9.27) and non-significant 2.6-fold increase in the adjusted OR (adjusted OR = 2.55; 95% CI = 0.86, 7.54) of ABL was observed among men with newly diagnosed Type 2 diabetes compared with the reference group (NGT combined with IFG). However, there was no association between IGT and ABL (adjusted OR = 0.99; 95% CI = 0.59,1.64). Conclusions Type 2 diabetes, but not IGT, was positively associated with ABL. Preventive maintenance against periodontitis is important in middle-aged men with diabetes. [source] Genetic polymorphisms of cyclooxygenase-2 and colorectal adenoma risk: The Self Defense Forces Health StudyCANCER SCIENCE, Issue 3 2008Naoyuki Ueda Cyclooxygenase (COX) is a key enzyme in the formation of prostaglandins, and an inducible isoform of COX, COX-2, has been implicated in colorectal carcinogenesis. This study investigated the relation of COX-2 polymorphisms (,1195G>A, ,765G>C and 8160A>G) to colorectal adenomas in a case,control study of male officials in the Self Defense Forces (SDF). The study subjects were 455 cases of colorectal adenoma and 1052 controls with no polyps who underwent total colonoscopy. Genotypes were determined using the polymerase chain reaction,restriction fragment length polymorphism (PCR-RFLP) method with genomic DNA extracted from the buffy coat. Statistical adjustment was made for age, hospital, rank in the SDF, body mass index (BMI), cigarette smoking, and alcohol intake. A statistically non-significant decrease in the risk of colorectal adenomas was observed for the AA versus GG genotype of ,1195G>A polymorphism and for the GC versus GG genotype of ,765G>C polymorphism. None had the ,765CC genotype in either the case or control groups. No effect modification of overweight, smoking or alcohol use was observed for either ,1195G>A or ,765G>C polymorphism. The variant allele of the 8160A>G polymorphism was extremely rare. A haplotype of ,1195G, ,765G and 8160A alleles was associated with a modest increase in the risk (adjusted odds ratio [OR] 1.38, 95% confidence interval [CI] 0.99,1.91), and the increase was more evident for distal adenomas (adjusted OR 1.57, 95% CI 1.04,2.38). Another haplotype of ,1195A, ,765C and 8160A alleles showed an adjusted OR of 0.22 (95% CI 0.06,0.88). These findings add to evidence for the role of COX-2 in colorectal carcinogenesis and warrant further studies focusing on haplotypes. (Cancer Sci 2008; 99: 576,581) [source] Possible age-associated bias in reporting of clinical features of drug dependence: epidemiological evidence on adolescent-onset marijuana useADDICTION, Issue 1 2003Chuan-Yu Chen ABSTRACT Aims, To probe recent evidence on apparent excess occurrence of marijuana dependence when marijuana smoking starts in adolescence. Design and participants, A national sample of recent-onset marijuana users was identified within public data files of the National Household Survey on Drug Abuse (NHSDA), 1995,98 (1866 adolescents and 762 adults). Measurements, Marijuana dependence was assessed via seven standardized questions about its clinical features, such as being unable to cut down. Multivariate response models (GLM/GEE and MIMIC) were used to evaluate adolescent excess risk and possible item biases. Findings, Among people who had just started to use marijuana, clinical features of marijuana dependence occurred twice as often among adolescents compared to adults, even with statistical adjustment for other covariates (P < 0.01 from GLM/GEE). MIMIC analyses suggest that adolescent-onset users have somewhat higher levels of marijuana dependence, and they also provide evidence of age-associated response bias for some but not all clinical features of marijuana dependence. That is, even with level of marijuana dependence held constant, adolescent recent-onset users were more likely than adults to report being unable to cut down (P = 0.01) and tolerance (P = 0.029). Conclusion, Nosologic, methodological and substantive reasons for observed age-related excess in occurrence of marijuana dependence problems among early onset users deserve more attention in future research. [source] An Examination of Rater Drift Within a Generalizability Theory FrameworkJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2009Polina Harik The present study examined the long-term usefulness of estimated parameters used to adjust the scores from a performance assessment to account for differences in rater stringency. Ratings from four components of the USMLEŽ Step 2 Clinical Skills Examination data were analyzed. A generalizability-theory framework was used to examine the extent to which rater-related sources of error could be eliminated through statistical adjustment. Particular attention was given to the stability of these estimated parameters over time. The results suggest that rater stringency estimates obtained at a point in time and then used to adjust ratings over a period of months may substantially decrease in usefulness. In some cases, over several months, the use of these adjustments may become counterproductive. Additionally, it is hypothesized that the rate of deterioration in the usefulness of estimated parameters may be a function of the characteristics of the scale. [source] Improved outcome of pediatric kidney transplantations in the Netherlands , Effect of the introduction of mycophenolate mofetil?PEDIATRIC TRANSPLANTATION, Issue 1 2005Karlien Cransberg Abstract:, Collaboration of the Dutch centers for kidney transplantation in children started in 1997 with a shared immunosuppressive protocol, aimed at improving graft survival by diminishing the incidence of acute rejections. This study compares the results of transplantations in these patients to those in a historical reference group. Ninety-six consecutive patients receiving a first kidney transplant were treated with an immunosuppressive regimen consisting of mycophenolate mofetil, cyclosporine and corticosteroids. The results were compared with those of historic controls (first transplants between 1985 and 1995, n = 207), treated with different combinations of corticosteroids, cyclosporine A and/or azathioprine. Cytomegalovirus (CMV) prophylaxis was prescribed to high-risk patients in the study group, and only a small proportion of the reference group. The graft survival at 1 yr improved significantly: 92% in the study group, vs. 73% in the reference group (p < 0.001). In the study group 63% of patients remained rejection-free during the first year; in the reference group 28% (p < 0.001). After statistical adjustment of differences in baseline data, as cold ischemia time, the proportion of LRD, preemptive transplantation, and young donors, the difference between study and reference group in graft survival (RR 0.33, p = 0.003) and incidence of acute rejection (RR 0.37, p < 0.001), as the only factor, remained statistically significant, indicating the effect of the immunosuppressive therapy. In the first year one case of malignancy occurred in each group. CMV disease occurred less frequently in the study group (11%) than in the reference group (26%, p = 0.02). As a new complication in 4 patients bronchiectasis was diagnosed. A new consensus protocol, including the introduction of mycophenolate mofetil, considerably improved the outcome of pediatric kidney transplantation in the Netherlands, measured as reduction of the incidence of acute rejection and improved graft survival. [source] Decreased lymphatic vessel counts in patients with systemic sclerosis: Association with fingertip ulcersARTHRITIS & RHEUMATISM, Issue 5 2010Alfiya Akhmetshina Objective Systemic sclerosis (SSc) is a connective tissue disease that is characterized by microvascular disease and tissue fibrosis. Progressive loss and irregular architecture of the small blood vessels are well characterized, but the potential involvement of the lymphatic vessel system has not been analyzed directly in SSc. This study was undertaken to assess whether the lymphatic vascular system is affected in SSc, and whether changes to the lymphatic vessels are associated with dystrophic changes and tissue damage in patients with SSc. Methods Lymphatic endothelial cells in skin biopsy samples from patients with SSc and age- and sex-matched healthy volunteers were identified by staining for podoplanin and prox-1, both of which are specifically expressed in lymphatic endothelial cells but not in blood vascular endothelial cells. CD31 was used as a pan,endothelial cell marker. Statistical analyses were performed using Kruskal-Wallis, Mann-Whitney U, and Spearman's rank correlation tests. Results The numbers of podoplanin- and prox-1,positive lymphatic vessels were significantly reduced in patients with SSc as compared with healthy individuals. The number of podoplanin-positive lymphatic precollector vessels was significantly lower in SSc patients with fingertip ulcers than in SSc patients without ulcers. Moreover, the number of lymphatic vessels correlated inversely with the number of fingertip ulcers at the time of biopsy and with the number of fingertip ulcers per year. The inverse correlation between lymphatic precollector vessel counts and fingertip ulcers remained significant after statistical adjustment for the blood vessel count, age, and modified Rodnan skin thickness score. Conclusion These results demonstrate a severe reduction in the number of lymphatic capillaries and lymphatic precollector vessels in patients with SSc. Patients with decreased lymphatic vessel counts may be at particularly high risk of developing fingertip ulcers. [source] A Copula Approach for Detecting Prognostic Genes Associated With Survival Outcome in Microarray StudiesBIOMETRICS, Issue 4 2007Kouros Owzar Summary A challenging and crucial issue in clinical studies in cancer involving gene microarray experiments is the discovery, among a large number of genes, of a relatively small panel of genes whose elements are associated with a relevant clinical outcome variable such as time-to-death or time-to-recurrence of disease. A semiparametric approach, using dependence functions known as copulas, is considered to quantify and estimate the pairwise association between the outcome and each gene expression. These time-to-event type endpoints are typically subject to censoring as not all events are realized at the time of the analysis. Furthermore, given that the total number of genes is typically large, it is imperative to control a relevant error rate in any gene discovery procedure. The proposed method addresses the two aforementioned issues by direct incorporation of the censoring mechanism and by appropriate statistical adjustment for multiplicity. The performance of the proposed method is studied through simulation and illustrated with an application using a case study in lung cancer. [source] Cigarette smoking is associated with suicidality in bipolar disorderBIPOLAR DISORDERS, Issue 7 2009Michael J Ostacher Objectives:, Cigarette smoking in individuals with bipolar disorder has been associated with suicidal behavior, although the precise relationship between the two remains unclear. Methods:, In this prospective observational study of 116 individuals with bipolar disorder, we examined the association between smoking and suicidality as measured by Linehan's Suicide Behaviors Questionnaire (SBQ) and prospective suicide attempts over a nine-month period. Impulsivity was measured by the Barratt Impulsiveness Scale. Results:, Smoking was associated with higher baseline SBQ scores in univariate and adjusted analyses, but was not significant after statistical adjustment for impulsivity in a regression model. A higher proportion of smokers at baseline made a suicide attempt during the follow-up period (5/31, 16.1%) compared to nonsmokers (3/85, 3.5%); p = 0.031, odds ratio = 5.25 (95% confidence interval: 1.2,23.5). Smoking at baseline also significantly predicted higher SBQ score at nine months. Conclusions:, In this study, current cigarette smoking was a predictor of current and nine-month suicidal ideation and behavior in bipolar disorder, and it is likely that impulsivity accounts for some of this relationship. [source] Infant and Neonatal Mortality for Primary Cesarean and Vaginal Births to Women with "No Indicated Risk," United States, 1998,2001 Birth CohortsBIRTH, Issue 3 2006Marian F. MacDorman PhD ABSTRACT:,Background: The percentage of United States' births delivered by cesarean section has increased rapidly in recent years, even for women considered to be at low risk for a cesarean section. The purpose of this paper is to examine infant and neonatal mortality risks associated with primary cesarean section compared with vaginal delivery for singleton full-term (37,41 weeks' gestation) women with no indicated medical risks or complications. Methods: National linked birth and infant death data for the 1998,2001 birth cohorts (5,762,037 live births and 11,897 infant deaths) were analyzed to assess the risk of infant and neonatal mortality for women with no indicated risk by method of delivery and cause of death. Multivariable logistic regression was used to model neonatal survival probabilities as a function of delivery method, and sociodemographic and medical risk factors. Results: Neonatal mortality rates were higher among infants delivered by cesarean section (1.77 per 1,000 live births) than for those delivered vaginally (0.62). The magnitude of this difference was reduced only moderately on statistical adjustment for demographic and medical factors, and when deaths due to congenital malformations and events with Apgar scores less than 4 were excluded. The cesarean/vaginal mortality differential was widespread, and not confined to a few causes of death. Conclusions: Understanding the causes of these differentials is important, given the rapid growth in the number of primary cesareans without a reported medical indication. (BIRTH 33:3 September 2006) [source] Skin-derived fibroblasts from long-lived species are resistant to some, but not all, lethal stresses and to the mitochondrial inhibitor rotenoneAGING CELL, Issue 1 2007James M. Harper Summary Fibroblast cell lines were developed from skin biopsies of eight species of wild-trapped rodents, one species of bat, and a group of genetically heterogeneous laboratory mice. Each cell line was tested in vitro for their resistance to six varieties of lethal stress, as well as for resistance to the nonlethal metabolic effects of the mitochondrial inhibitor rotenone and of culture at very low glucose levels. Standard linear regression of species-specific lifespan against each species mean stress resistance showed that longevity was associated with resistance to death induced by cadmium and hydrogen peroxide, as well as with resistance to rotenone inhibition. A multilevel regression method supported these associations, and suggested a similar association for resistance to heat stress. Regressions for resistance to cadmium, peroxide, heat, and rotenone remained significant after various statistical adjustments for body weight. In contrast, cells from longer-lived species did not show significantly greater resistance to ultraviolet light, paraquat, or the DNA alkylating agent methylmethanesulfonate. There was a strong correlation between species longevity and resistance to the metabolic effects of low-glucose medium among the rodent cell lines, but this test did not distinguish mice and rats from the much longer-lived little brown bat. These results are consistent with the idea that evolution of long-lived species may require development of cellular resistance to several forms of lethal injury, and provide justification for evaluation of similar properties in a much wider range of mammals and bird species. [source] | ||||||||||