Home About us Contact
|
Home About us Contact | ||
|
|
||
Residual Confounding (residual + confounding)
Selected AbstractsWeaknesses of goodness-of-fit tests for evaluating propensity score models: the case of the omitted confounder,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 4 2005Sherry Weitzen PhD Abstract Purpose Propensity scores are used in observational studies to adjust for confounding, although they do not provide control for confounders omitted from the propensity score model. We sought to determine if tests used to evaluate logistic model fit and discrimination would be helpful in detecting the omission of an important confounder in the propensity score. Methods Using simulated data, we estimated propensity scores under two scenarios: (1) including all confounders and (2) omitting the binary confounder. We compared the propensity score model fit and discrimination under each scenario, using the Hosmer,Lemeshow goodness-of-fit (GOF) test and the c-statistic. We measured residual confounding in treatment effect estimates adjusted by the propensity score omitting the confounder. Results The GOF statistic and discrimination of propensity score models were the same for models excluding an important predictor of treatment compared to the full propensity score model. The GOF test failed to detect poor model fit for the propensity score model omitting the confounder. C-statistics under both scenarios were similar. Residual confounding was observed from using the propensity score excluding the confounder (range: 1,30%). Conclusions Omission of important confounders from the propensity score leads to residual confounding in estimates of treatment effect. However, tests of GOF and discrimination do not provide information to detect missing confounders in propensity score models. Our findings suggest that it may not be necessary to compute GOF statistics or model discrimination when developing propensity score models. Copyright © 2004 John Wiley & Sons, Ltd. [source] Early weaning and alcohol disorders in offspring: biological effect, mediating factors or residual confounding?ADDICTION, Issue 8 2009Rosa Alati ABSTRACT Aims This study explores associations between early weaning and alcohol use disorders in youth and mechanisms by which these associations may operate. Design We used data from the Mater University Study of Pregnancy and its outcomes, an Australian birth cohort study based in Brisbane. Setting and participants: This study is based on a subsample of 2370 participants for whom complete data were available at age 21 years. Length and method of breastfeeding were assessed at 6 months. Measurements Alcohol use disorders were assessed at age 21 using the life-time version of the Composite International Diagnostic Interview,computerized version (CIDI-Auto). We adjusted for maternal age, marital status, education, alcohol, tobacco use, anxiety, depression and maternal attitudes towards the baby. Attention Deficit and Hyperactivity Disorders (ADHD) and Intellect Quotient (IQ) were measured with the Child Behaviour Checklist (5 years) and the Ravens SM (14 years), respectively. Findings Those who had been weaned within 2 weeks of being born and breastfed at regular intervals were at increased risk of meeting criteria for alcohol use disorders at age 21 [odds ratio (OR) 1.71, 95% confidence interval (CI):1.07, 2.72]. Conclusion This study confirms a small but robust association between early weaning and increased risk of alcohol use disorders. [source] Effect of Statin (HMG-Co-A-Reductase Inhibitor) Use on 1-Year Mortality and Hospitalization Rates in Older Patients with Cardiovascular Disease Living in Nursing HomesJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 8 2002Charles B. Eaton MD OBJECTIVES: To quantify the effect of statins on 1-year mortality, hospitalizations, and decline in physical function among patients with cardiovascular disease (CVD) aged 65 and older living in nursing homes. DESIGN: Retrospective cohort study. SETTING: All Medicare/Medicaid certified nursing homes (N = 1,492) in Maine, New York, Mississippi, and South Dakota. PARTICIPANTS: We identified 51,559 older patients with CVD from a population database that merged sociodemographic data and functional, clinical, and drug treatments from more than 300,000 newly admitted nursing home residents from 1992 to 1997. Statin users (n = 1,313) were matched with nonusers (n = 1,313) in the same facilities. MEASUREMENTS: All-cause mortality, hospitalization, combined endpoint of mortality or hospitalization, and decline in physical function were determined at 1 year, and survival analysis was performed. RESULTS: Prevalence of statin use in this frail older cohort with CVD was 2.6%. Statin use varied by age, gender, comorbid condition, medication use, and cognitive and physical function. One-year mortality was 229/1,000 person-years in the statin group and 404/1,000 person-years in the nonusers, with an adjusted hazard rate ratio (HRR) of 0.69, 95% confidence interval (CI) = 0.58,0.81. The estimated number needed to treat was seven (95% CI = 5,13). This association with improved all-cause mortality was evident for women and men and for age groups 75 to 84, and 85 and older. CONCLUSION: Statin therapy is associated with improved clinical outcomes, including reduction in 1-year all-cause mortality, and the combined endpoint of death or hospitalization in a frail older population with CVD. Some caution should be taken in interpreting these results because potential bias from residual confounding could affect these results. [source] Outcomes following early red blood cell transfusion in acute upper gastrointestinal bleedingALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 2 2010S. A. Hearnshaw Aliment Pharmacol Ther 2010; 32: 215,224 Summary Background, Acute upper gastrointestinal bleeding (AUGIB) accounts for 14% of RBC units transfused in the UK. In exsanguinating AUGIB the value of RBC transfusion is self evident, but in less severe bleeding its value is less obvious. Aim, To examine the relationship between early RBC transfusion, re-bleeding and mortality following AUGIB, which is one of the most common indications for red blood cell (RBC) transfusion. Method, Data were collected on 4441 AUGIB patients presenting to UK hospitals. The relationship between early RBC transfusion, re-bleeding and death was examined using logistic regression. Results, 44% were transfused RBCs within 12 hours of admission. In patients transfused with an initial haemoglobin of <8 g/dl, re-bleeding occurred in 23% and mortality was 13% compared with a re-bleeding rate of 15%, and mortality of 13% in those not transfused. In patients transfused with haemoglobin >8 g/dl, re-bleeding occurred in 24% and mortality was 11% compared with a re-bleeding rate of 6.7%, and mortality of 4.3% in those not transfused. After adjusting for Rockall score and initial haemoglobin, early transfusion was associated with a two-fold increased risk of re-bleeding (Odds ratio 2.26, 95% CI 1.76,2.90) and a 28% increase in mortality (Odds ratio 1.28, 95% CI 0.94,1.74). Conclusions, Early RBC transfusion in AUGIB was associated with a two-fold increased risk of re-bleeding and an increase in mortality, although the latter was not statistically significant. Although these findings could be due to residual confounding, they indicate that a randomized comparison of restrictive and liberal transfusion policies in AUGIB is urgently required. [source] Mendelian randomization in nutritional epidemiologyNUTRITION REVIEWS, Issue 8 2009Lu Qi Nutritional epidemiology aims to identify dietary and lifestyle causes for human diseases. Causality inference in nutritional epidemiology is largely based on evidence from studies of observational design, and may be distorted by unmeasured or residual confounding and reverse causation. Mendelian randomization is a recently developed methodology that combines genetic and classical epidemiological analysis to infer causality for environmental exposures, based on the principle of Mendel's law of independent assortment. Mendelian randomization uses genetic variants as proxies for environmental exposures of interest. Associations derived from Mendelian randomization analysis are less likely to be affected by confounding and reverse causation. During the past 5 years, a body of studies examined the causal effects of diet/lifestyle factors and biomarkers on a variety of diseases. The Mendelian randomization approach also holds considerable promise in the study of intrauterine influences on offspring health outcomes. However, the application of Mendelian randomization in nutritional epidemiology has some limitations. [source] Analgesic use and the risk for progression of chronic kidney disease,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 7 2010Hsin-Wei Kuo Abstract Purpose The chronic effect of various analgesics on the progression of chronic kidney disease (CKD) is inconclusive. There is also lack of information on the renal safety of selective cyclooxygenase-2 (COX-2) inhibitors. This study aimed to clarify the renal risk of analgesic use in CKD patients. Methods A cohort study using a nationally representative database randomly sampled from National Health Insurance (NHI) enrollees was performed. The study population included a total of 19,163 newly diagnosed CKD patients. Clinical conditions were defined by diagnostic codes and exposure information on analgesics was derived from service claims. Cox proportional hazard model was used to assess the association between analgesic use and the risk of progression to end stage renal disease (ESRD). Results CKD patients using acetaminophen, aspirin, and non-selective non-steroidal anti-inflammatory drugs (NSAIDs) had an increased risk for ESRD with multivariable-adjusted HRs (95%CIs) of 2.92 (2.47,3.45), 1.96 (1.62,2.36), and 1.56 (1.32,1.85), respectively. The trends toward higher risk with increasing exposure dose were significant for all classes of analgesics (all P for trend,<,0.001). Among COX-2 inhibitors, only rofecoxib, but not celecoxib, shows a significant risk association with ESRD (HR,=,1.98; 95%CI, 1.15,3.40). Conclusions Our data indicated exacerbating effects of acetaminophen, aspirin, and non-selective NSAIDs on CKD in a dose-dependent manner. For COX-2 inhibitors, only rofecoxib showed an increased risk for ESRD. Although the possibility of residual confounding cannot be completely ruled out, given the common use of analgesics, the possible relation suggested by this study warrants further investigation. Copyright © 2010 John Wiley & Sons, Ltd. [source] Sensitivity analysis and external adjustment for unmeasured confounders in epidemiologic database studies of therapeutics,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 5 2006Sebastian Schneeweiss MD Abstract Background Large health care utilization databases are frequently used to analyze unintended effects of prescription drugs and biologics. Confounders that require detailed information on clinical parameters, lifestyle, or over-the-counter medications are often not measured in such datasets, causing residual confounding bias. Objective This paper provides a systematic approach to sensitivity analyses to investigate the impact of residual confounding in pharmacoepidemiologic studies that use health care utilization databases. Methods Four basic approaches to sensitivity analysis were identified: (1) sensitivity analyses based on an array of informed assumptions; (2) analyses to identify the strength of residual confounding that would be necessary to explain an observed drug-outcome association; (3) external adjustment of a drug-outcome association given additional information on single binary confounders from survey data using algebraic solutions; (4) external adjustment considering the joint distribution of multiple confounders of any distribution from external sources of information using propensity score calibration. Conclusion Sensitivity analyses and external adjustments can improve our understanding of the effects of drugs and biologics in epidemiologic database studies. With the availability of easy-to-apply techniques, sensitivity analyses should be used more frequently, substituting qualitative discussions of residual confounding. Copyright © 2006 John Wiley & Sons, Ltd. [source] Prenatal PCB exposure and neurobehavioral development in infants and children: Can the Oswego study inform the current debate?PSYCHOLOGY IN THE SCHOOLS, Issue 6 2004Paul Stewart In the current paper we describe the methodology and results of the Oswego study, in light of D.V. Cicchetti, A.S. Kaufman, and S.S. Sparrow's (this issue) criticisms regarding the validity of the human health/behavioral claims in the PCB literature. The Oswego project began as a replication of the Lake Michigan Maternal Infant Cohort study. Beyond replication of the Michigan findings, the study sought to extend results and conclusions through more comprehensive behavioral assessment, and improved confounder control and analytic methodology. Results over the past 5 years have demonstrated a convincing replication of the Michigan findings. The Michigan cohort reported findings relating Great Lakes fish consumption to performance impairments on the Neonatal Behavioral Assessment Scale (J. Jacobson, S. Jacobson, P. Schwartz, G. Fein, & J. Dowler, 1984). These findings were also found in the Oswego cohort (E. Lonky, J. Reihman, T. Darvill, J. Mather, & H. Daly, 1996), and the Oswego study extended the association to cord blood PCBS (P.W. Stewart, J. Reihman, E. Lonky, and T. Darvill, 2000). The Michigan cohort reported an association between prenatal PCB exposure and poorer performance on the Fagan Test of Infant Intelligence (S.W. Jacobson, G.G. Fein, J.L. Jacobson, P.M. Schwartz, & J.K. Dowler, 1985). The Oswego cohort found similar results (T. Darvill, E. Lonky, J. Reihman, P. Stewart, & J. Pagano, 2000). The Michigan Cohort reported an association between prenatal PCB exposure and performance impairments on the McCarthy Scales of Children's abilities (J. Jacobson & S. Jacobson, 1997). The Oswego study also found PCB-related impairments on the McCarthy Scales (P.W. Stewart, J. Reihman, E. Lonky, T. Darvill, & J. Pagano, 2003). The Oswego results used the same exposure metric in every paper, employed conservative statistical design and analysis, and controlled for more than 40 potentially confounding variables. Moreover, while PCBs were related to all the behavioral endpoints outlined above, alternative candidates for effect, including lead, HCB, Mirex, DDE, and MeHg were not. Taken together, these results support the hypothesis that prenatal PCB exposure results in statistically significant predictors of small, but measurable, deficits in cognitive development from infancy through early childhood. Cicchetti et al. argue that these results, generated by independent investigators, be dismissed because they reflect a combination of measurement error, Type I error, and residual confounding. The evidence Cicchetti et al. present in support of their position fails to explain the nearly identical pattern of associations observed in the Oswego and Michigan Cohorts. In light of this replication, the extensive assessment of potential confounders, the effective elimination of alternative contaminants, and the conservative statistical approach employed in the Oswego study, we find that Cicchetti et al.'s claims are not substantiated. © 2004 Wiley Periodicals, Inc. Psychol Schs 41: 639,653, 2004. [source] Breastfeeding and school achievement in Brazilian adolescentsACTA PAEDIATRICA, Issue 11 2005CESAR G. VICTORA Abstract Aim: To assess the effect of breastfeeding duration on school achievement in a Brazilian cohort. Methods: In a population-based birth cohort, we analysed the highest grade achieved in school of over 2000 male 18-y-olds relative to breastfeeding information collected in early life. Analyses were adjusted for birthweight, family income, maternal and paternal schooling, household assets, number of siblings, social class, maternal smoking during pregnancy, and ethnicity. Results: After adjustment for confounding variables, there was a highly significant trend in school achievement with increasing breastfeeding duration. Those breastfed for 9 mo or more were ahead by 0.5,0.8 school grades, relative to those breastfed for less than 1 mo. Data from a cross-sectional survey in the same population suggest that such a difference corresponds to a 10,15% difference in adult income levels. The duration of exclusive or predominant breastfeeding was also positively associated with schooling. Conclusion: Unlike studies from developed countries, there was no clear association between breastfeeding duration and either the family's socio-economic level or parental schooling in our sample and therefore residual confounding is improbable. These results suggest that the impact of breastfeeding on intellectual development may lead to sizeable differences in adult education and wage-earning performance. [source] | ||||||||||