Home About us Contact
|
Home About us Contact | ||
|
|
||
Multiple Potential Confounders (multiple + potential_confounder)
Selected AbstractsHelicobacter pylori Infection and Iron Stores: A Systematic Review and Meta-analysisHELICOBACTER, Issue 5 2008Khitam Muhsen Abstract Background and Aims:, We carried out a systematic literature review and meta-analysis to evaluate the existing evidence on the association between Helicobacter pylori infection and iron stores. Methods:, Twelve case reports and case series, 19 observational epidemiologic studies and six intervention trials were included in the review. Results:, Although only few studies controlled for multiple potential confounders, most studies reported a positive association, linking between H. pylori and decreased body iron stores in symptomatic and asymptomatic H. pylori -infected subjects. H. pylori infection may be regarded as a risk factor for reduction in body iron stores and also for iron deficiency or iron deficiency anemia, especially in high-risk groups. The results of the meta-analysis of thoroughly designed and analyzed studies revealed an increased risk for iron deficiency anemia; pooled odds ratio (OR) 2.8 (95% confidence interval (CI) 1.9, 4.2) and also for iron deficiency; pooled OR 1.38 (95%CI 1.16,1.65) among H. pylori -infected subjects. The biologic mechanism by which H. pylori induces the alteration in the iron stores is not fully understood, but it seems to involve several pathways, including gastrointestinal blood loss, decrease in the absorption of dietary iron, and enhanced uptake of the iron by the bacterium. Conclusions:,H. pylori is associated with reduced iron stores. Future research is needed to determine whether this relationship is a causal association and to better understand its biologic mechanism. The impact of anti- H. pylori therapy on improvement of iron stores needs to be further evaluated in large and well-controlled trials. [source] Fatigue Predicts Mortality in Older AdultsJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 10 2008Susan E. Hardy MD OBJECTIVES: To determine the association between fatigue and survival over 10 years in a population of older community-dwelling primary care patients. DESIGN: Prospective cohort study. SETTING: Medicare health maintenance organization and Veterans Affairs primary care programs. PARTICIPANTS: Older primary care patients (N=492). MEASUREMENTS: Fatigue, operationalized as feeling tired most of the time, was assessed at baseline. Mortality was ascertained from the National Death Index. Covariates included demographics, comorbidity, cognitive function, depressive symptoms, body mass index, self-rated health, functional status, and gait speed. RESULTS: Mortality rates at 10 years were 59% (123/210) for older adults with fatigue, versus 38% (106/282) for those without fatigue (P<.001). After adjustment for multiple potential confounders, participants who were tired at baseline had a greater risk of death than those who were not (hazard ratio=1.44, 95% confidence interval=1.08,1.93). CONCLUSION: A single simple question "Do you feel tired most of the time?" identifies older adults with a higher risk of mortality. Further research is needed to identify and characterize the underlying mechanisms of fatigue, to develop and test specific treatments, and to determine whether improvement leads to decreased morbidity and mortality. [source] Criteria for confounders in epidemiological studiesJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES B (STATISTICAL METHODOLOGY), Issue 1 2002Zhi Geng The paper addresses a formal definition of a confounder based on the qualitative definition that is commonly used in standard epidemiology text-books. To derive the criterion for a factor to be a confounder given by Miettinen and Cook and to clarify inconsistency between various criteria for a confounder, we introduce the concepts of an irrelevant factor, an occasional confounder and a uniformly irrelevant factor. We discuss criteria for checking these and show that Miettinen and Cook's criterion can also be applied to occasional confounders. Moreover, we consider situations with multiple potential confounders, and we obtain two necessary conditions that are satisfied by each confounder set. None of the definitions and results presented in this paper require the ignorability and sufficient control confounding assumptions which are commonly employed in observational and epidemiological studies. [source] Protracted CRP Elevation after Atrial Fibrillation AblationPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 9 2008JAMES M. McCABE M.D. Background: Atrial fibrillation (AF) has been linked to an inflammatory process detected through various biomarkers, including C-Reactive Protein (CRP). Early recurrence of AF within the first 3 months after curative AF ablation is not felt to reflect success or failure of the procedure. We hypothesized that this early recurrence is due to an inflammatory response to the ablation itself. We therefore sought to evaluate levels of CRP after AF ablation. Methods: We prospectively enrolled subjects undergoing AF ablation. A control group of patients undergoing ablation for supraventricular tachycardia (SVT) was also enrolled. Each patient had CRP drawn on the day of the procedure (prior to ablation) and during their first follow-up (median 49 days, interquartile range [IQR] 37,93) and second follow-up (median 147 days, IQR 141,257) clinic visits. Patient interviews were performed and medical histories reviewed for evidence of recurrent AF prior to the first follow-up. Results: CRP levels significantly increased from baseline to first follow-up in the AF ablation group (P = 0.0017). CRP did not significantly change after SVT ablation (P = 0.92). Seventeen (45%) of the AF subjects exhibited recurrence of AF prior to first follow-up. After adjusting for multiple potential confounders, AF ablation patients with recurrent AF prior to their first follow-up had a statistically significant greater odds of having an increase in CRP (OR 21, 95% CI 1.1,417, P = 0.045). Conclusions: AF ablation generates an inflammatory response that persists for several weeks. This inflammation may explain early recurrence of AF after curative ablation. [source] | ||||||||||