Home About us Contact
|
Home About us Contact | ||
|
|
||
Hazards Regression (hazard + regression)
Kinds of Hazards Regression Terms modified by Hazards Regression Selected AbstractsMarginal Hazards Regression for Retrospective Studies within Cohort with Possibly Correlated Failure Time DataBIOMETRICS, Issue 2 2009Sangwook Kang Summary A retrospective dental study was conducted to evaluate the degree to which pulpal involvement affects tooth survival. Due to the clustering of teeth, the survival times within each subject could be correlated and thus the conventional method for the case,control studies cannot be directly applied. In this article, we propose a marginal model approach for this type of correlated case,control within cohort data. Weighted estimating equations are proposed for the estimation of the regression parameters. Different types of weights are also considered for improving the efficiency. Asymptotic properties of the proposed estimators are investigated and their finite sample properties are assessed via simulations studies. The proposed method is applied to the aforementioned dental study. [source] A cohort study to examine whether time and risk preference is related to smoking cessation successADDICTION, Issue 6 2009Rei Goto ABSTRACT Aim To identify whether time and risk preference predicts relapse among smokers trying to quit. Design A cohort study of smokers who had recently started to quit. Time and risk preference parameters were estimated using a discrete choice experiment (DCE). Participants A total of 689 smokers who began quitting smoking within the previous month. Measurements Time discount rate, coefficient of risk-aversion measured at study entry and duration of smoking cessation measured for 6 months. Findings In the unadjusted model, Cox's proportional hazard regression showed that those with a high time discount rate were more likely to relapse [hazard ratio: 1.18, 95% confidence interval (CI): 1.11,1.25]. A high coefficient of risk-aversion reduced the hazard of relapse (0.96, 0.96,0.97). When adjusted for other predictors of relapse (age, gender, self-efficacy of quitting, health status, mood variation, past quitting experience, the use of nicotine replacement therapy, nicotine dependence), the hazard ratios of time discount rate and the coefficient of risk-aversion is 1.17 (95% CI: 1.10,1.24) and 0.98 (95% CI: 0.97,0.99), respectively. Conclusions Those who emphasize future rewards (time,patient preference) and those who give more importance to rewards that are certain (higher risk-aversion) were significantly more likely to continue to abstain from smoking. [source] Comparing alternative models: log vs Cox proportional hazard?HEALTH ECONOMICS, Issue 8 2004Anirban Basu Abstract Health economists often use log models (based on OLS or generalized linear models) to deal with skewed outcomes such as those found in health expenditures and inpatient length of stay. Some recent studies have employed Cox proportional hazard regression as a less parametric alternative to OLS and GLM models, even when there was no need to correct for censoring. This study examines how well the alternative estimators behave econometrically in terms of bias when the data are skewed to the right. Specifically we provide evidence on the performance of the Cox model under a variety of data generating mechanisms and compare it to the estimators studied recently in Manning and Mullahy (2001). No single alternative is best under all of the conditions examined here. However, the gamma regression model with a log link seems to be more robust to alternative data generating mechanisms than either OLS on ln(y) or Cox proportional hazards regression. We find that the proportional hazard assumption is an essential requirement to obtain consistent estimate of the E(y,x) using the Cox model. Copyright © 2004 John Wiley & Sons, Ltd. [source] Performance of a World Health Organization first-line regimen (stavudine/lamivudine/nevirapine) in antiretroviral-naïve individuals in a Western settingHIV MEDICINE, Issue 5 2007LWY Tam Objectives In 2003, the World Health Organization (WHO) and Joint United Nations Programme on HIV/AIDS (UNAIDS) introduced the ,3 by 5 Initiative' to treat 3 million individuals by the end of 2005. This study evaluates the time to treatment termination, viral load suppression, and detection of drug resistance among antiretroviral-naïve individuals initiating stavudine/lamivudine/nevirapine (d4T/3TC/NVP) in British Columbia, Canada, to provide a context for future programme planning. Methods Primary outcome was time to treatment termination. Secondary outcome was time to viral suppression. Accumulation of drug resistance mutations was followed systematically in the first 145 individuals over 30 months. Cox proportional hazard regression identified factors associated with termination and suppression. Results 312 antiretroviral-naïve individuals initiated d4T/3TC/NVP between August 1996 and September 2003. Median follow-up time was 26.5 months (interquartile range [IQR] 6.8,46.5). At a median of 12.4 months (IQR 4.3,33.3), 132 (42.3%) patients switched treatment, 53 (17.0%) stopped therapy and 26 (8.3%) died. Of 308 subjects with baseline viral load >500 copies/mL, 223 (72.4%) suppressed to ,500 copies/mL at a median of 2.0 months. Among 145 (46.5%) individuals followed longitudinally, resistance mutations to NNRTI, 3TC, or other NRTI were detected in 11 (7.6%), six (4.1%) and four (2.8%) individuals after 12 months of therapy; and in 23 (15.9%), 17 (12.0%), and six (4.1%) individuals after 30 months. Conclusions The population requiring second-line treatment was 30% at 12 months and 40% at 24 months; 20% had detectable drug resistance mutations by 30 months. While these results are from a Western setting, they illustrate the need to consider second- and third-line approaches as antiretroviral treatment scale-up continues in the developing world. [source] Predictors of entering 24-h care for people with Alzheimer's disease: results from the LASER-AD studyINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 11 2009Stephanie Habermann Abstract Objectives Many studies have investigated predictors of people with dementia entering 24-h care but this is the first to consider a comprehensive range of carer and care recipient (CR) characteristics derived from a systematic review, in a longitudinal cohort study followed up for several years. Methods We interviewed 224 people with Alzheimer's disease (AD) and their carers, recruited to be representative in terms of their severity, sex and living situation as part of the LASER-AD study; and determined whether they entered 24-h care in the subsequent 4.5,years. We tested a comprehensive range of characteristics derived from a systematic review, and used Cox proportional hazard regression to determine whether they independently predicted entering 24-h care. Results The main independent predictors of shorter time to enter 24-h care were the patient being: more cognitively or functionally impaired (hazard ratio (HR),=,1.09; 95% CI,=,1.06,1.12) and (HR,=,1.04 95% CI,=,1.03,1.05), having a paid versus a family carer (HR,=,2.22; 95% CI,=,1.39,3.57), the carer being less educated (HR,=,1.43; 95% CI,=,1.12,1.83) and spending less hours caring (HR,=,1.01; 95% CI,=,1.00,1.01). Conclusion As having a family carer who spent more time caring (taking into account illness severity) delayed entry to 24-h care, future research should investigate how to enable carers to provide this. Other interventions to improve patients' impairment may not only have benefits for patients' health but also allow them to remain longer at home. This financial benefit could more than offset the treatment cost. Copyright © 2009 John Wiley & Sons, Ltd. [source] Low donor-to-recipient weight ratio does not negatively impact survival of pediatric heart transplant patientsPEDIATRIC TRANSPLANTATION, Issue 6 2010Liwen Tang Tang L, Du W, Delius RE, L'Ecuyer TJ, Zilberman MV. Low donor-to-recipient weight ratio does not negatively impact survival of pediatric heart transplant patients. Pediatr Transplantation 2010: 14:741,745. © 2010 John Wiley & Sons A/S. Abstract:, A major limitation to success in pediatric heart transplantation is donor organ shortage. While the use of allografts from donors larger than the recipient is accepted, the use of undersized donor grafts is generally discouraged. Using the UNOS database, we wanted to evaluate whether using smaller donor hearts affects the short- and long-term survival of pediatric heart transplant patients. A retrospective analysis of data entered into the UNOS database from April 1994 to May 2008 was performed. Pediatric heart transplant recipients (ages 0,18 yr) with DRWR <2.0 were identified and divided into two groups: Low-DRWR (<0.8) and Ideal-DRWR (0.8,2.0). Patients' demographics, pretransplant diagnoses, age at transplantation, severity of pretransplant condition, and rate of complications prior to hospital discharge after transplantation were noted. Fisher's exact, chi-square, and Wilcoxon rank sum tests were used to compare patients' baseline characteristics. Kaplan,Meier curves and Cox proportional hazard regression were used to compare patients' survival and to identify independent risk factors for outcomes. There were 3048 patients (204 with Low- and 2844 with Ideal-DRWR). The Low-ratio group patients were older (8.3 vs. 6.9 yr; p = 0.001), there was a slight male predominance in the Low-DRWR group (p = 0.055). The Low-DRWR group had longer transplant wait time than the Ideal-DRWR group (97 vs. 85 days; p = 0.04). The groups did not differ in race, primary diagnoses, severity of pretransplant condition (medical urgency status, need for ventilation, inotropic support, ECMO, nitric oxide, or dialysis, the PVR for those with bi-ventricular anatomy), or post-transplant complications (length of stay, need for inotropic support, dialysis, and rate of infections). The Low-DRWR patients had less episodes of acute rejection during the first-post-transplant month. Infants with DRWR 0.5,0.59 had lower 30-day survival rate (p = 0.045). There was no difference in short- and long-term survival between the patients with DRWR 0.6,0.79 and DRWR 0.8,2.0. Use of smaller allografts (DRWR 0.6,0.8) has no negative impact on the short- and long-term survival of pediatric heart transplant patients. [source] Risk factors for suicide following hospital discharge among cancer patientsPSYCHO-ONCOLOGY, Issue 10 2009Herng-Ching Lin Abstract Objectives: This study aims to examine risk factors associated with 3-month post-discharge suicide among cancer patients using Taiwan's nationwide, population-based datasets. Methods: The study cohort comprised all cancer patients discharged from hospitals from 2002 to 2004, inclusive, who committed suicide within 90 days of discharge (n=311). The control group consisted of 1555 cancer patients who did not commit suicide within 90 days of discharge. The dependent variable was whether or not a patient committed suicide within 90 days of discharge, while the independent variables included patient, hospital and physician characteristics at index hospitalization. Cox proportional hazard regression was carried out to compute the 90-day survival rate, adjusting for possible confounding factors. Results: The mean interval from discharge to suicide was 39.7 days (±95.2) and almost half (46.3%) of the 3-month post-discharge suicides occurred within 14 days after discharge. The adjusted hazard of committing suicide for patients who were not hospitalized in the preceding year was 1.68 (p=0.009), 1.61 (p=0.033), and 2.51 (p<0.001) times greater, respectively, than patients who were hospitalized once, twice and more than twice within the year before index hospitalization. The hazard of committing suicide among patients who were unemployed was 1.71 (p<0.001) times that of their employed counterparts. Conclusions: We conclude that, while our study was limited to suicides among cancer patients within 90 days of discharge, around 60% of deaths occurred within the first month after discharge. The relevant risk factors include the number of hospitalizations within 1 year and employment status. Copyright © 2009 John Wiley & Sons, Ltd. [source] Influence of duration of sexual cohabitation on the risk of hypertension in nulliparous parturients in Ibadan: A cohort studyAUSTRALIAN AND NEW ZEALAND JOURNAL OF OBSTETRICS AND GYNAECOLOGY, Issue 1 2010Oladapo OLAYEMI Background:, Hypertensive disorders of pregnancy are an important cause of maternal mortality in this environment, it accounts for about 20% of all maternal deaths in pregnancy in Nigeria. Aim:, This study aims to determine the effect of the length of sexual cohabitation on the development of hypertension in pregnancy in a Nigerian population. Materials and methods:, The study was a prospective cohort study; three centres were involved in the study between July 2006 and February 2009. For this study, the main outcome variable was the development of Hypertension in pregnancy. The main explanatory variable was the length of preconception sexual cohabitation. Univariate analysis was by t test, chi-squared test and Fisher's exact test for continuous and categorical variables. Multivariate analysis was by Cox hazard regression Results:, In the study population, the incidence of gestational hypertension and pre-eclampsia were 28.93% and 4.13% respectively, 29.64% had previous abortions and same paternity abortion rate was 25.92%. Length of sexual cohabitation before index pregnancy was protective against hypertension in pregnancy but not for pre-eclampsia; there was a 4% decrease in the risk of developing hypertension for every month increase in cohabitation (hazard ratio, HR 0.96 (95% CI 0.93,0.99)). Also protective in this model was same paternity abortion with a HR of 0.71 (95% CI 0.55,0.93). A previous abortion was not protective (HR 1.05 (95% CI 0.82,1.35)). Conclusion:, It was concluded that increased length of sexual cohabitation prior to conception reduces the risk of gestational hypertension. [source] Joint Spatial Modeling of Recurrent Infection and Growth with Processes under Intermittent ObservationBIOMETRICS, Issue 2 2010F. S. Nathoo Summary In this article, we present a new statistical methodology for longitudinal studies in forestry, where trees are subject to recurrent infection, and the hazard of infection depends on tree growth over time. Understanding the nature of this dependence has important implications for reforestation and breeding programs. Challenges arise for statistical analysis in this setting with sampling schemes leading to panel data, exhibiting dynamic spatial variability, and incomplete covariate histories for hazard regression. In addition, data are collected at a large number of locations, which poses computational difficulties for spatiotemporal modeling. A joint model for infection and growth is developed wherein a mixed nonhomogeneous Poisson process, governing recurring infection, is linked with a spatially dynamic nonlinear model representing the underlying height growth trajectories. These trajectories are based on the von Bertalanffy growth model and a spatially varying parameterization is employed. Spatial variability in growth parameters is modeled through a multivariate spatial process derived through kernel convolution. Inference is conducted in a Bayesian framework with implementation based on hybrid Monte Carlo. Our methodology is applied for analysis in an 11-year study of recurrent weevil infestation of white spruce in British Columbia. [source] Bacillus Calmette-Guérin therapy in stage Ta/T1 bladder cancer: prognostic factors for time to recurrence and progressionBJU INTERNATIONAL, Issue 7 2004P. Andius OBJECTIVE To report prognostic factors for time to recurrence and progression after bacillus Calmette-Guérin (BCG) prophylaxis in patients with stage Ta/T1 papillary bladder cancer. PATIENTS AND METHODS The clinical records were assessed retrospectively for 236 patients with papillary stage Ta/T1 bladder cancer treated with BCG between 1986 and 2000. Patients with known carcinoma in situ were excluded. The median (range) follow-up was 44 (4,155) months. The effect of 13 variables on the time to recurrence and progression was evaluated using multivariate Cox proportional hazard regression and Kaplan-Meier analyses. RESULTS The recurrence rate was markedly reduced for all grades and stages. Patients with a negative first cystoscopy and maintenance BCG had a significantly longer time to recurrence than those treated with an induction course alone (P < 0.001). Thirty-seven patients (16%) progressed in stage. The result of the first cystoscopy (P < 0.001), tumour grade (P = 0.003) and six or fewer initial instillations (P = 0.002) had prognostic importance for the time to progression. Twenty-eight patients (12%) had a history of an upper tract tumour, which was 3,10 times the expected rate. Age, number of tumours, number of positive cystoscopies, length of tumour history before BCG, BCG strain and treatment year had no influence on time to recurrence and progression. CONCLUSIONS Maintenance treatment does not seem to be necessary among patients with TaG1-G2 disease after a negative first cystoscopy, as the progression rate was very low. One new finding was that BCG seemed to be equally effective among patients with or with no history of an upper tract tumour. Another new and surprising finding was that patients treated with fewer than six induction instillations, because of very bothersome side-effects, had an increased risk of tumour progression and of local failure. [source] Elevated serum urate concentration independently predicts poor outcome following stroke in patients with diabetesDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 1 2006Edward J. Newman Abstract Background Type 2 diabetes is a risk factor for stroke and confers increased risk of poor outcome and further vascular events following stroke. Hyperuricaemia occurs commonly in patients with type 2 diabetes, but its significance as a predictor of outcome following stroke is uncertain. We sought to investigate the prognostic significance of elevated serum urate concentration in diabetic subjects following stroke. Methods We studied a cohort of type 2 diabetes patients presenting to our unit with computed tomography-confirmed acute stroke. Fasting blood samples were drawn within 24 h of admission for urate concentration and standard battery of biochemistry and hematological tests. Information on age, stroke type, prior hypertension, smoking status, resolution time of symptoms and National Institutes of Health Stroke Score was collated. The main outcome event was time to myocardial infarction, recurrent stroke or vascular death, as defined in the CAPRIE trial. Stepwise proportional hazards regression was used to estimate the effect of the above variables on event-free survival following stroke. Results One hundred and forty patients were studied. Median follow-up duration was 974 days (IQR 163 to 1830 days). Sixty-four patients suffered an outcome event. Urate levels of greater than 0.42 mmol/L (p < 0.001) and an increasing NIHSS score (p < 0.001) independently predicted increased likelihood of suffering an event. Conclusion Elevated urate concentration is significantly and independently associated with increased risk of future vascular events in diabetic stroke patients. Further studies to elucidate the mechanism of this observation are required. Copyright © 2005 John Wiley & Sons, Ltd. [source] Methadone maintenance therapy promotes initiation of antiretroviral therapy among injection drug usersADDICTION, Issue 5 2010Sasha Uhlmann ABSTRACT Aims Despite proven benefits of antiretroviral therapy (ART), many human immunodeficiency virus (HIV)-infected injection drug users (IDU) do not access treatment even in settings with free health care. We examined whether methadone maintenance therapy (MMT) increased initiation and adherence to ART among an IDU population with free health care. Design We examined prospectively a cohort of opioid-using antiretroviral-naive HIV-infected IDU and investigated factors associated with initiation of antiretroviral therapy as well as subsequent adherence. Factors associated independently with time to first initiation of antiretroviral therapy were modelled using Cox proportional hazards regression. Findings Between May 1996 and April 2008, 231 antiretroviral-naive HIV-infected opioid-using IDU were enrolled, among whom 152 (65.8%) initiated ART, for an incidence density of 30.5 [95% confidence interval (CI): 25.9,35.6] per 100 person-years. After adjustment for time-updated clinical characteristics and other potential confounders, use of MMT was associated independently with more rapid uptake of antiretroviral therapy [relative hazard = 1.62 (95% CI: 1.15,2.28); P = 0.006]. Those prescribed methadone also had higher rates of ART adherence after first antiretroviral initiation [odds ratio = 1.49 (95% CI: 1.07,2.08); P = 0.019]. Conclusion These results demonstrate that MMT contributes to more rapid initiation and subsequent adherence to ART among opioid-using HIV-infected IDU. Addressing international barriers to the use and availability of methadone may increase dramatically uptake of HIV treatment among this population. [source] Inflammation reduces HDL protection against primary cardiac riskEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 6 2010James P. Corsetti Eur J Clin Invest 2010; 40 (6): 483,489 Abstract Background, We recently reported high high-density lipoprotein (HDL) cholesterol as a predictor of recurrent risk in a subgroup of postinfarction patients defined by hypercholesterolemia and high C-reactive protein (CRP) levels. We investigated whether a similar high-risk subgroup might exist for incident cardiovascular disease. Material and Methods, A graphical exploratory data analysis tool was used to identify high-risk subgroups in a male population-based cohort (n = 3405) from the prevention of renal and vascular end-stage disease study by generating 3-dimensional mappings of risk over the HDL-cholesterol/CRP domain with subsequent use of Kaplan,Meier analysis to verify high-risk. Within-subgroup risk was assessed using Cox proportional hazards regression and Kaplan,Meier analysis. Results, Mappings revealed two high-risk subgroups: a low HDL-cholesterol/high CRP subgroup and a high HDL-cholesterol/high CRP subgroup. The low HDL-cholesterol subgroup demonstrated a pattern of metabolic syndrome dyslipidemia contrasted with a predominantly unremarkable biomarker pattern for the high HDL-cholesterol subgroup. However, in the high HDL-cholesterol subgroup, CRP levels were higher than the low HDL-cholesterol subgroup; and within the high HDL-cholesterol subgroup, CRP predicted risk. Moreover, in the high HDL-cholesterol subgroup, risk was associated with lower triglyceride levels in conjunction with presumptively larger HDL particles. Conclusions, High HDL-cholesterol and high CRP levels define a subgroup of men at high-risk for incident cardiovascular disease. High HDL cholesterol-associated risk likely relates to impaired HDL particle remodelling in the setting of inflammation. This approach may facilitate identification of additional inflammation-related mechanisms underlying high HDL cholesterol-associated risk; and potentially influence management of such patients. [source] Impact of treating facilities' volume on survival for early-stage laryngeal cancer,HEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 9 2009Amy Y. Chen MD Abstract Background Treatment at a high-volume facility has been associated with better outcomes in a variety of conditions. The relationship between volume and survival from laryngeal cancer has not been examined previously. Methods A total of 11,446 early-stage laryngeal cancer patients (1996,1998) who reported to the National Cancer Database (NCDB) were analyzed. Proportional hazards regression was used to assess the relationship between survival and treatment volume controlling for other factors associated with survival. Results Treatment at low-volume facilities was associated with a significantly increased likelihood of death (hazard ratio 1.20, 95% CI 1.04,1.38). Surgical resection, as compared with radiation treatment, was associated with lower mortality (HR 0.74, 95% CI 0.69,0.80). Conclusion This study is the first to assess the relationship between survival and treatment volume in laryngeal cancer. Treatment at a high-volume facility is associated with better survival. Surgical treatment rather than radiation was also associated with better survival, although we could not control for confounders that may bias treatment selection. © 2009 Wiley Periodicals, Inc. Head Neck, 2009 [source] Comparing alternative models: log vs Cox proportional hazard?HEALTH ECONOMICS, Issue 8 2004Anirban Basu Abstract Health economists often use log models (based on OLS or generalized linear models) to deal with skewed outcomes such as those found in health expenditures and inpatient length of stay. Some recent studies have employed Cox proportional hazard regression as a less parametric alternative to OLS and GLM models, even when there was no need to correct for censoring. This study examines how well the alternative estimators behave econometrically in terms of bias when the data are skewed to the right. Specifically we provide evidence on the performance of the Cox model under a variety of data generating mechanisms and compare it to the estimators studied recently in Manning and Mullahy (2001). No single alternative is best under all of the conditions examined here. However, the gamma regression model with a log link seems to be more robust to alternative data generating mechanisms than either OLS on ln(y) or Cox proportional hazards regression. We find that the proportional hazard assumption is an essential requirement to obtain consistent estimate of the E(y,x) using the Cox model. Copyright © 2004 John Wiley & Sons, Ltd. [source] Superior virological response to boosted protease inhibitor-based highly active antiretroviral therapy in an observational treatment programmeHIV MEDICINE, Issue 2 2007E Wood Background The use of boosted protease inhibitor (PI)-based antiretroviral therapy has become increasingly recommended in international HIV treatment consensus guidelines based on the results of randomized clinical trials. However, the impact of this new treatment strategy has not yet been evaluated in community-treated cohorts. Methods We evaluated baseline characteristics and plasma HIV RNA responses to unboosted and boosted PI-based highly active antiretroviral therapy (HAART) among antiretroviral-naïve HIV-infected patients in British Columbia, Canada who initiated HAART between August 1997 and September 2003 and who were followed until September 2004. We evaluated time to HIV-1 RNA suppression (<500 HIV-1 RNA copies/mL) and HIV-1 RNA rebound (,500 copies/mL), while stratifying patients into those that received boosted and unboosted PI-based HAART as the initial regimen, using Kaplan,Meier methods and Cox proportional hazards regression. Results During the study period, 682 patients initiated therapy with unboosted PI and 320 individuals initiated HAART with a boosted PI. Those who initiated therapy with a boosted PI were more likely to have a CD4 cell count <200 cells/,L and to have a plasma HIV RNA>100 000 copies/mL, and to have AIDS at baseline (all P<0.001). However, when we examined virological response rates, those who initiated HAART with a boosted PI achieved more rapid virological suppression [relative hazard 1.26, 95% confidence interval (CI) 1.06,1.51, P=0.010]. Conclusions Patients prescribed boosted PIs achieved superior virological response rates despite baseline factors that have been associated with inferior virological responses to HAART. Despite the inherent limitations of observational studies which require this study be interpreted with caution, these findings support the use of boosted PIs for initial HAART therapy. [source] Incidence and Prognosis of Colorectal Dysplasia in Inflammatory Bowel Disease: A Population-based Study from Olmsted County, Minnesota,INFLAMMATORY BOWEL DISEASES, Issue 8 2006Tine Jess MD Abstract Background and Aims: The risk, fate, and ideal management of colorectal dysplasia in inflammatory bowel disease (IBD) remain debated. We estimated the incidence, long-term outcome, and risk factors for progression of colorectal dysplasia (adenomas [adenoma-associated lesions or masses (ALMs)], flat dysplasia, and dysplasia-associated lesions or masses [DALMs]) in a population-based IBD cohort from Olmsted County, Minnesota. Materials and Methods: The Rochester Epidemiology Project was used to identify cohort patients with colorectal dysplasia. Medical records were reviewed for demographic and clinical characteristics. Histology slides were reviewed by a pathologist blinded to previous pathology reports. The cumulative incidence of dysplasia was estimated, and the association between patient characteristics and recurrence/progression of dysplasia was assessed using proportional hazards regression. Results: Twenty-nine (4%) IBD patients developed flat dysplasia (n = 8), DALMs (n = 1), ALMs in areas of IBD (n = 18), or ALMs outside areas of IBD (n = 2). Among 6 patients with flat low-grade dysplasia (fLGD) who did not undergo colectomy, none progressed during a median of 17.8 (range 6,21) years of observation with a median of 3 (range 0,12) surveillance colonoscopies. Four (22%) patients with ALMs in areas of IBD who did not undergo surgery developed LGD or DALMs. Primary sclerosing cholangitis and dysplasia located proximal to the splenic flexure were significantly associated with risk for recurrence/progression of dysplasia. Conclusions: This population-based cohort study from Olmsted County, Minnesota did not confirm an increased risk of cancer related to fLGD, whereas 22% of patients with ALMs in areas of IBD developed fLGD or DALMs. [source] Prostate cancer and PSA among statin users in the Finnish prostate cancer screening trialINTERNATIONAL JOURNAL OF CANCER, Issue 7 2010Teemu J. Murtola Abstract Decreased risk of advanced prostate cancer has been reported among men using statins. However, the evidence on overall prostate cancer risk is conflicting. We compared the relative risk between current users and non-users of statins or other cholesterol-lowering medications in a population undergoing systematical prostate cancer screening. The study cohort comprised of 23,320 men participating in the screening arm of the Finnish prostate cancer screening trial during 1996,2004. Information on medication use was obtained from a comprehensive national prescription database. Cox proportional hazards regression was used to calculate multivariable adjusted hazard ratios (HRs) for prostate cancer. Serum prostate-specific antigen (PSA) level was compared between current users and non-users of cholesterol-lowering drugs. Compared with medication non-users, the overall prostate cancer incidence was decreased among statin users [HR 0.75, 95% confidence interval (CI) 0.63,0.89]. The inverse association was dose-dependent with cumulative amount of statin use, and strongest for low-grade and early stage tumors. The incidence was nonsignificantly lower also among users of other types of cholesterol-lowering drugs (HR 0.62, 95% CI 0.28,1.38), but without dose-dependence. Age-adjusted median serum PSA tended to be lower among users of cholesterol-lowering drugs, but the relative risk decrease among statin users was not related to decreased PSA. Overall incidence of prostate cancer was lowered among statin users when bias due to differential PSA testing between medication users and non-users was eliminated by systematical prostate cancer screening. Cholesterol-lowering with statins seems beneficial for prostate cancer prevention. [source] Hypertension is an independent predictor of survival disparity between African-American and white breast cancer patientsINTERNATIONAL JOURNAL OF CANCER, Issue 5 2009Dejana Braithwaite Abstract The objective of this study was to determine whether comorbidity, or pre-existing conditions, can account for some of the disparity in survival between African-American and white breast cancer patients. A historical cohort study was conducted of 416 African-American and 838 white women diagnosed with breast cancer between 1973 and 1986, and followed through 1999 in the Kaiser Permanente Northern California Medical Care Program. Information on comorbidity, tumor characteristics and breast cancer treatment was obtained from medical records, and Surveillance, Epidemiology and End Results, Northern California Cancer Center Registry. Associations between comorbidity and survival were analyzed with multiple Cox proportional hazards regression. Over a mean follow-up of 9 years, African Americans had higher overall crude mortality than whites: 165 (39.7%) versus 279 (33.3%), respectively. When age, race, tumor characteristics and breast cancer treatment were controlled, the presence of hypertension was associated with all cause survival [hazard ratio (HR) = 1.33, 95% confidence intervals (CI) 1.07,1.67] and it accounted for 30% of racial disparity in this outcome. Hypertension-augmented Charlson Comorbidity Index was a significant predictor of survival from all causes (HR = 1.32, 95%CI 1.18,1.49), competing causes (HR = 1.52, 95%CI 1.32,1.76) and breast cancer specific causes (HR = 1.18, 95%CI 1.03,1.35). In conclusion, hypertension has prognostic significance in relation to survival disparity between African-American and white breast cancer patients. If our findings are replicated in contemporary cohorts, it may be necessary to include hypertension in the Charlson Comorbidity Index and other comorbidity measures. © 2008 Wiley-Liss, Inc. [source] A prospective study of dietary flavonoid intake and incidence of epithelial ovarian cancerINTERNATIONAL JOURNAL OF CANCER, Issue 10 2007Margaret A. Gates Abstract Flavonoids are antioxidant compounds found in plants, including fruits, vegetables and tea. No prior prospective studies have examined the association between intake of flavonoids in the flavonol and flavone subclasses and ovarian cancer risk. We analyzed the association between intake of 5 common dietary flavonoids and incidence of epithelial ovarian cancer among 66,940 women in the Nurses' Health Study. We calculated each participant's intake of myricetin, kaempferol, quercetin, luteolin and apigenin from dietary data collected at multiple time points, and used Cox proportional hazards regression to model the incidence rate ratio (RR) of ovarian cancer for each quintile of intake. Our analysis included 347 cases diagnosed between 1984 and 2002, and 950,347 person-years of follow-up. There was no clear association between total intake of the 5 flavonoids examined and incidence of ovarian cancer (RR = 0.75 for the highest versus lowest quintile, 95% confidence interval [CI] = 0.51,1.09). However, there was a significant 40% decrease in ovarian cancer incidence for the highest versus lowest quintile of kaempferol intake (RR = 0.60, 95% CI = 0.42,0.87; p -trend = 0.002), and a significant 34% decrease in incidence for the highest versus lowest quintile of luteolin intake (RR = 0.66, 95% CI = 0.49,0.91; p -trend = 0.01). There was evidence of an inverse association with consumption of tea (nonherbal) and broccoli, the primary contributors to kaempferol intake in our population. These data suggest that dietary intake of certain flavonoids may reduce ovarian cancer risk, although additional prospective studies are needed to further evaluate this association. If confirmed, these results would provide an important target for ovarian cancer prevention. © 2007 Wiley-Liss, Inc. [source] Finite Element Analysis of the Proximal Femur and Hip Fracture Risk in Older Men,JOURNAL OF BONE AND MINERAL RESEARCH, Issue 3 2009Eric S Orwoll Abstract Low areal BMD (aBMD) is associated with increased risk of hip fracture, but many hip fractures occur in persons without low aBMD. Finite element (FE) analysis of QCT scans provides a measure of hip strength. We studied the association of FE measures with risk of hip fracture in older men. A prospective case-cohort study of all first hip fractures (n = 40) and a random sample (n = 210) of nonfracture cases from 3549 community-dwelling men ,65 yr of age used baseline QCT scans of the hip (mean follow-up, 5.6 yr). Analyses included FE measures of strength and load-to-strength ratio and BMD by DXA. Hazard ratios (HRs) for hip fracture were estimated with proportional hazards regression. Both femoral strength (HR per SD change = 13.1; 95% CI: 3.9,43.5) and the load-to-strength ratio (HR = 4.0; 95% CI: 2.7,6.0) were strongly associated with hip fracture risk, as was aBMD as measured by DXA (HR = 5.1; 95% CI: 2.8,9.2). After adjusting for age, BMI, and study site, the associations remained significant (femoral strength HR = 6.5, 95% CI: 2.3,18.3; load-to-strength ratio HR = 4.3, 95% CI: 2.5,7.4; aBMD HR = 4.4, 95% CI: 2.1,9.1). When adjusted additionally for aBMD, the load-to-strength ratio remained significantly associated with fracture (HR = 3.1, 95% CI: 1.6,6.1). These results provide insight into hip fracture etiology and demonstrate the ability of FE-based biomechanical analysis of QCT scans to prospectively predict hip fractures in men. [source] Proportional hazards estimate of the conditional survival functionJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 4 2000Ronghui Xu We introduce a new estimator of the conditional survival function given some subset of the covariate values under a proportional hazards regression. The new estimate does not require estimating the base-line cumulative hazard function. An estimate of the variance is given and is easy to compute, involving only those quantities that are routinely calculated in a Cox model analysis. The asymptotic normality of the new estimate is shown by using a central limit theorem for Kaplan,Meier integrals. We indicate the straightforward extension of the estimation procedure under models with multiplicative relative risks, including non-proportional hazards, and to stratified and frailty models. The estimator is applied to a gastric cancer study where it is of interest to predict patients' survival based only on measurements obtained before surgery, the time at which the most important prognostic variable, stage, becomes known. [source] Role of gender and race mismatch and graft failure in patients undergoing liver transplantationLIVER TRANSPLANTATION, Issue 6 2002Vinod K. Rustgi MD Previous data have suggested an increased risk of graft failure in male recipients of female livers, and in nonwhite recipients of orthotopic liver transplantation. United Network for Organ Sharing records of liver transplantations from 1992 through 2000 with at least one follow-up visit were reviewed. Analysis of these data was performed with proportional hazards regression, controlling for follow-up time, age, gender, ethnicity, number of comorbidities, functional status at time of transplant, and status 1 designation. Separate analyses comparing transplants among whites and blacks only and matched versus mismatched transplants for male and female recipients were performed. The results revealed that gender-mismatched patients (n = 13,992) had a higher likelihood of graft failure when compared with gender matched transplants (n = 18,522) (12.2% versus 11.3% respectively, P = .013). After controlling for the above potential confounders, gender-mismatched patients were found to have a 6.9% increase in likelihood of graft failure, (P = .042). Female recipients receiving male organs had no significant change in the risk of graft failure (11.5%; P = .368). A worse outcome was found in male recipients receiving female organs (12.9%; P = .0003). Graft failure rate among patients with donors matched by race (white to white or nonwhite to nonwhite; n = 21,818) was 11.6% versus 11.9%, and among unmatched patients (n = 10,697), the difference was not significant (P = .33). Multivariate regression analysis controlling for potential confounders confirmed that this difference was not significant (P = .21). Mismatch between black donors and white recipients was found to increase the risk of liver graft failure (27.4%, P = < .0001), independently of gender, number of comorbidities, and functional status at time of transplant. [source] Have studies of urinary tract infection and preterm delivery used the most appropriate methods?PAEDIATRIC & PERINATAL EPIDEMIOLOGY, Issue 3 2003Marie S. O'Neill Summary Published investigations of the association between urinary tract infection (UTI) and preterm delivery used logistic regression or chi-squared tests. Because both exposure and outcome are time dependent, these methods were not optimal and did not account for person,time under observation, potentially an important feature given the variability of women's entry to prenatal care as well as of gestational lengths. Previous researchers probably classified as exposed some women whose UTI occurred after their pregnancies exceeded 37 weeks. We applied the previous analytical methods to 1990,93 births from two Durham, NC, USA, hospitals (n = 4053) and demonstrate survival methods as an alternative. Two logistic regression models were fitted with differing exposure definitions: model 1 in which exposed = UTI diagnosed after 20 weeks' gestation; and model 2 in which exposed = UTI diagnosed between 20 weeks' and 37 weeks' gestation. Model 3 used proportional hazards regression with person,time after 20 weeks and before UTI diagnosis as unexposed, and person,time after diagnosis as exposed. Models were fit with and without five time-constant potential confounders. Model 1 yielded an adjusted odds ratio (OR) of 0.8 [95% confidence interval (CI) 0.5, 1.2], and model 2, which did not include UTI diagnoses after 37 weeks, an adjusted OR of 0.9 [95% CI 0.6, 1.4]. The Cox model hazard ratio (HR) for preterm delivery was 1.1 (adjusted) [95% CI 0.7, 1.7]. As these results indicated some bias, but not remarkable differences, we conducted a sensitivity analysis using 100 samples of 80% of the original data set, with replacement to determine how large the differences might be in other, similar data sets. The Cox method consistently produced higher effect estimates than either logistic model. The two samples with the greatest differences between the Cox and logistic model estimates yielded an OR of 1.47 [95% CI 0.95, 2.29] for model 1 vs. HR of 2.06 [95% CI 1.39, 3.06] for model 3, and an OR of 1.41 [95% CI 0.88, 2.25] for model 2 vs. HR of 1.79 [95% CI 1.17, 2.71] for model 3 respectively. Previous published results on UTI and preterm delivery require cautious interpretation. Data on UTI timing should be gathered to allow appropriate analyses; survival methods account for person,time under observation and ensure that studied exposures precede effects. [source] Adjuvant chemotherapy for stage C colonic cancer in a multidisciplinary settingANZ JOURNAL OF SURGERY, Issue 10 2009Pierre H. Chapuis Abstract Background:, In this study of patients undergoing adjuvant chemotherapy for clinicopathological stage C colonic cancer after optimal surgery, the aims were: to describe their immediate experience of chemotherapy, to assess disease-free survival, to compare overall survival with that of a matched untreated historical control group, and to evaluate the associations between previously identified adverse risk factors and survival. Methods:, Data were drawn from a comprehensive, prospective hospital registry of resections for colorectal cancer between 1971 and 2004, with retrospective data on adjuvant chemotherapy. The main end point was overall survival. Statistical analysis employed the chi-squared test, Kaplan,Meier estimation and proportional hazards regression. Results:, From May 1992 to December 2004, there were 104 patients who received adjuvant chemotherapy. Duration of treatment, withdrawal from treatment, toxicity and other immediate treatment outcomes were similar to those in other equivalent studies. There were no toxicity-associated deaths. Overall survival was significantly longer in the treated patients than in the control group (3-year rates 81% and 66%, respectively, P = 0.009). A significant protective effect of adjuvant therapy was found (hazard ratio 0.5, 95% confidence interval 0.3,0.8, P = 0.001) after adjustment for histopathology features previously shown to be negatively associated with survival (high grade, venous invasion, apical node metastasis, free serosal surface involvement). Conclusions:, For patients who have had a curative resection for lymph node positive colonic cancer in a specialist colorectal surgical unit and been managed by a multidisciplinary team, post-operative adjuvant chemotherapy is safe and provides the same survival advantage as seen in randomized trials. [source] Endometrial cells as a predictor of uterine cancerAUSTRALIAN AND NEW ZEALAND JOURNAL OF OBSTETRICS AND GYNAECOLOGY, Issue 1 2007Adrian R. HEARD Abstract Background:, With the recent cervix screening national guidelines recommending against reporting of benign endometrial cells, we examined South Australian data to see what impact this would have on detecting uterine cancers. Aims:, To test whether benign endometrial cells detected in cervical cytology testing confer an increased risk of uterine cancer, and to ascertain what percentage of uterine cancers will be missed in cervical screening programs if these cells are not reported. Methods:, The study was a retrospective cohort design of 1585 women with shed endometrial cells, each matched with three women without shed cells. All were linked with cancer registry data to check for uterine cancer diagnosis. Cox proportional hazards regression was used to check for any increase in cancer risk with shed endometrial cells. Using the calculated relative risks for uterine cancer diagnosis, we estimated the number of uterine cancers in South Australia associated with benign endometrial cells. Results:, The presence of benign endometrial cells in a cervical cytology test increases the risk of uterine cancer sixfold. However, screening women with benign cells would involve a major increase in pathology work for only an 18% increase in uterine cancers detected. Conclusions:, Until cytology systems have a higher sensitivity in detecting which benign endometrial cells are associated with uterine cancer, pathology laboratories are unlikely to be required to report these cells on tests. Inability to adjust for symptomatic status may have reduced the relevance of the results in this study. [source] Benchmarking epidemiological characteristics of cervical cancer in advance of change in screening practice and commencement of vaccinationAUSTRALIAN AND NEW ZEALAND JOURNAL OF PUBLIC HEALTH, Issue 2 2007Colin Luke Abstract Objectives: To investigate trends in cervical cancer incidence, mortality and survival by histology for benchmarking purposes ahead of practice change and the introduction of Human Papilloma Virus (HPV) vaccine. Methods: Using data from the South Australian Cancer Registry, age-standardised rates are presented for four-year periods from 1977 to 2004. Socio-demographic and secular predictors of glandular as opposed to squamous cancers are investigated, using multivariable logistic regression. Disease-specific survivals are analysed using Kaplan-Meier product-limit estimates and Cox proportional hazards regression. Results: Incidence and mortality rates reduced by 55.1% and 59.3% respectively between 1977,80 and 2001,04, with larger reductions for squamous than glandular cancers. The ratio of squamous to glandular cancer incidence reduced from 5.4:1 in 1977,88 to 2.8:1 in 1993,2004, with a corresponding reduction from 5.2:1 to 3.0:1 for mortality. Compared with squamous cancers, glandular lesions were more common in patients from higher socio-economic areas, but less common in those over 70 years of age, Aboriginal patients, and those born in Southern Europe. Conclusion: The proportion of cancers comprising glandular lesions has increased, possibly reflecting prevention of squamous cancers through treatment of screen-detected preinvasive lesions. Additional mortality reductions from screening may be limited where the proportion of glandular lesions is high, with vaccination offering the best prospects for gains in the long term. Priority should be given to Aboriginal and Torres Strait Islander women in vaccination programs in view of their high death rate from cervical cancer. [source] Fast FSR Variable Selection with Applications to Clinical TrialsBIOMETRICS, Issue 3 2009Dennis D. Boos Summary A new version of the false selection rate variable selection method of Wu, Boos, and Stefanski (2007,,Journal of the American Statistical Association,102, 235,243) is developed that requires no simulation. This version allows the tuning parameter in forward selection to be estimated simply by hand calculation from a summary table of output even for situations where the number of explanatory variables is larger than the sample size. Because of the computational simplicity, the method can be used in permutation tests and inside bagging loops for improved prediction. Illustration is provided in clinical trials for linear regression, logistic regression, and Cox proportional hazards regression. [source] A Semiparametric Estimate of Treatment Effects with Censored DataBIOMETRICS, Issue 3 2001Ronghui Xu Summary. A semiparametric estimate of an average regression effect with right-censored failure time data has recently been proposed under the Cox-type model where the regression effect ,(t) is allowed to vary with time. In this article, we derive a simple algebraic relationship between this average regression effect and a measurement of group differences in K -sample transformation models when the random error belongs to the Gp family of Harrington and Fleming (1982, Biometrika69, 553,566), the latter being equivalent to the conditional regression effect in a gamma frailty model. The models considered here are suitable for the attenuating hazard ratios that often arise in practice. The results reveal an interesting connection among the above three classes of models as alternatives to the proportional hazards assumption and add to our understanding of the behavior of the partial likelihood estimate under nonproportional hazards. The algebraic relationship provides a simple estimator under the transformation model. We develop a variance estimator based on the empirical influence function that is much easier to compute than the previously suggested resampling methods. When there is truncation in the right tail of the failure times, we propose a method of bias correction to improve the coverage properties of the confidence intervals. The estimate, its estimated variance, and the bias correction term can all be calculated with minor modifications to standard software for proportional hazards regression. [source] The independent value of tumour volume in a contemporary cohort of men treated with radical prostatectomy for clinically localized diseaseBJU INTERNATIONAL, Issue 4 2010Sima P. Porten Study Type , Prognosis (case series) Level of Evidence 4 OBJECTIVE To determine if prostate tumour volume is an independent prognostic factor in a contemporary cohort of men who had a radical prostatectomy (RP) for clinically localized disease, as the effect of tumour volume on prostate cancer outcomes has not been consistently shown in the era of widespread screening with prostate-specific antigen (PSA). PATIENTS AND METHODS The study included 856 men who had RP from 1998 to 2007 for localized prostate cancer. Tumour volume based on pathology was analysed as a continuous and categorized (<0.26, 0.26,0.50, 0.51,1.00, 1.01,2.00, 2.01,4.00, >4.00 mL) variable using Cox proportional hazards regression and Kaplan-Meier analysis. A multivariable analysis was also conducted controlling for PSA level, Gleason grade, surgical margins, and pathological stage. RESULTS Tumour volume had a positive association with grade and stage, but did not correlate with biochemical recurrence-free survival on univariate analysis as a continuous variable (hazard ratio 1.00, P = 0.09), and was only statistically significant for volumes of >4 mL as a categorical variable. No tumour volume was an independent predictor of prostate cancer recurrence on multivariate analysis. There was no difference between tumour volume and time to cancer recurrence for organ-confined tumours using Kaplan-Meier analysis. In low-risk patients (PSA level <10 ng/mL, Gleason score ,6, clinical stage T1c/T2a) tumour volume did not correlate with biochemical recurrence-free survival in univariate or multivariable analysis. CONCLUSIONS There is no evidence that tumour volume is an independent predictor of prostate cancer outcome and it should not be considered as a marker of tumour risk, behaviour or prognosis. [source] | |||||||||||||||||||||||||