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Possible Confounding (possible + confounding)
Terms modified by Possible Confounding Selected AbstractsCaffeine, cognitive failures and health in a non-working community sampleHUMAN PSYCHOPHARMACOLOGY: CLINICAL AND EXPERIMENTAL, Issue 1 2009Andrew P Smith Abstract Rationale Most studies of the effects of caffeine on performance have been conducted in the laboratory and further information is required on the real-life effects of caffeine consumption on cognition. In addition, possible effects of caffeine consumption on a range of health outcomes should also be assessed in these studies to enable cost-benefit analyses to be conducted. Objectives Secondary analyses of a large epidemiological database (N,=,3223 non-working participants, 57% female, with a mean age of 49.6 years, range 17,92 years) were conducted to examine associations between caffeine consumption (mean caffeine consumption was 140,mg/day, range 0,1800,mg) and cognitive failures (errors of memory, attention and action) in a non-working sample. Associations between caffeine consumption and physical and mental health problems were also examined. Methods The study involved secondary analyses of a database formed by combining the Bristol Stress and Health at Work and Cardiff Health and Safety at Work studies. Associations between caffeine consumption and frequency of cognitive failures and health outcomes were examined in a sample of non-workers. Results After controlling for possible confounding factors significant associations between caffeine consumption and fewer cognitive failures were observed. Initial analyses suggested that many health variables were associated with regular level of caffeine consumption. However, most of the significant effects of caffeine disappeared when demographic and lifestyle factors were controlled for. Consumption of caffeine was, however, associated with a reduced risk of depression. These effects were also observed in separate analyses examining the source of the caffeine (coffee and tea). Conclusions Overall, the results show that caffeine consumption may benefit cognitive functioning in a non-working population. This confirms earlier findings from working samples. This beneficial effect of caffeine was not associated with negative health consequences. Indeed, consumption of caffeine was found to be associated with a reduced risk of depression. Copyright © 2008 John Wiley & Sons, Ltd. [source] Monitoring processes with data censored owing to competing risks by using exponentially weighted moving average control chartsJOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 3 2001Stefan H. Steiner In industry, process monitoring is widely employed to detect process changes rapidly. However, in some industrial applications observations are censored. For example, when testing breaking strengths and failure times often a limited stress test is performed. With censored observations, a direct application of traditional monitoring procedures is not appropriate. When the censoring occurs due to competing risks, we propose a control chart based on conditional expected values to detect changes in the mean strength. To protect against possible confounding caused by changes in the mean of the censoring mechanism we also suggest a similar chart to detect changes in the mean censoring level. We provide an example of monitoring bond strength to illustrate the application of this methodology. [source] Long-term study of re-infection following successful eradication of Helicobacter pylori infectionALIMENTARY PHARMACOLOGY & THERAPEUTICS, Issue 9 2006E. A. B. CAMERON Summary Background ,Re-infection' with Helicobacter pylori after eradication has been estimated to occur in 0,14% of patients, although most so-called ,re-infections' occur within the first year following ,eradication' and many may actually be due to recrudescence of a temporarily suppressed infection. Aim To study the true re-infection rate, we have studied re-infection rates after eradication therapy by excluding the first year's data, minimizing the possible confounding effect of recrudescence. Methods All patients tested for H. pylori infection following eradication therapy between 1987 and 2004 were evaluated. Testing was carried out by urea breath test and gastric biopsy. Patients were included if they were found to be negative for H. pylori infection by testing at least 1 year following eradication and underwent at least one further test for H. pylori. Results 1162 patients met the inclusion criteria with median post-eradication follow-up of 3 years (1.5,14) including 4668 tests; 3319 years of follow-up were analysed. Thirteen cases of re-infection occurred (re-infection rate 0.4% per year). Conclusions This large study of H. pylori re-infection avoided cases of recrudescence by excluding the first post-eradication year. True re-infection is probably less common than previously thought. [source] No association between partial depopulation and Campylobacter spp. colonization of Dutch broiler flocksLETTERS IN APPLIED MICROBIOLOGY, Issue 3 2005A.D. Russa Abstract Aims:, To determine whether an association exists between partial depopulation of a flock and increased Campylobacter colonization in that flock. Methods and Results:, Data from 1737 flocks of two Dutch integrators were used. Flocks that experienced partial depopulation were defined as ,exposed' and those that did not as ,nonexposed'. Multivariable modelling was accomplished with, in addition to ,exposure', the independent variables ,age of broilers at slaughter' and ,season' to adjust for possible confounding. The response variable was ,Campylobacter colonization'. The odds ratio (OR) for partial depopulation for integrator A was 0·8 [95% CI (0·4, 1·8)]; for integrator B the OR = 0·8 [95% CI (0·5, 1·3)]. Age and season were confounders: the difference in Campylobacter status between exposed and nonexposed flocks of integrator A could be explained by both variables; for integrator B, only season was associated with Campylobacter status. Conclusions:, We found no significant association between partial depopulation and an increased risk of Campylobacter colonization among broiler flocks at final depopulation. Significance and Impact of the Study:, This study demonstrates that Campylobacter colonization in a broiler flock is not influenced by the partial depopulation of that flock. [source] Impact of publicly sponsored interventions on musculoskeletal injury claims in nursing homes,AMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 9 2009Robert M. Park MS Abstract Background The rate of lost-time sprains and strains in private nursing homes is over three times the national average, and for back injuries, almost four times the national average. The Ohio Bureau of Workers' Compensation (BWC) has sponsored interventions that were preferentially promoted to nursing homes in 2000,2001, including training, consultation, and grants up to $40,000 for equipment purchases. Methods This study evaluated the impact of BWC interventions on back injury claim rates using BWC data on claims, interventions, and employer payroll for all Ohio nursing homes during 1995,2004 using Poisson regression. A subset of nursing homes was analyzed with more detailed data that allowed estimation of the impact of staffing levels and resident acuity on claim rates. Costs of interventions were compared to the associated savings in claim costs. Results A $500 equipment purchase per nursing home worker was associated with a 21% reduction in back injury rate. Assuming an equipment life of 10 years, this translates to an estimated $768 reduction in claim costs per worker, a present value of $495 with a 5% discount rate applied. Results for training courses were equivocal. Only those receiving below-median hours had a significant 19% reduction in claim rates. Injury rates did not generally decline with consultation independent of equipment purchases, although possible confounding, misclassification, and bias due to non-random management participation clouds interpretation. In nursing homes with available data, resident acuity was modestly associated with back injury risk, and the injury rate increased with resident-to-staff ratio (acting through three terms: RR,=,1.50 for each additional resident per staff member; for the ratio alone, RR,=,1.32, 95% CI,=,1.18,1.48). In these NHs, an expenditure of $908 per resident care worker (equivalent to $500 per employee in the other model) was also associated with a 21% reduction in injury rate. However, with a resident-to-staff ratio greater than 2.0, the same expenditure was associated with a $1,643 reduction in back claim costs over 10 years per employee, a present value of $1,062 with 5% discount rate. Conclusions Expenditures for ergonomic equipment in nursing homes by the Ohio BWC were associated with fewer worker injuries and reductions in claim costs that were similar in magnitude to expenditures. Un-estimated benefits and costs also need to be considered in assessing full health and financial impacts. Am. J. Ind. Med. 52:683,697, 2009. © 2009 Wiley-Liss, Inc. [source] The protective effect of antimalarial drugs on thrombovascular events in systemic lupus erythematosusARTHRITIS & RHEUMATISM, Issue 3 2010Hyejung Jung Objective The antimalarial medication hydroxychloroquine has been proposed as a thromboprotective agent in systemic lupus erythematosus (SLE), but studies thus far have been limited by the possibility of confounding by indication. This study was conducted to assess whether exposure to antimalarial drugs is associated with a decrease in thrombovascular events (TEs) in patients with SLE. Methods The study was designed as a nested case,control study embedded in an inception cohort of patients with SLE, which allowed adjustments for possible confounding by calendar year, duration of disease, duration of observation, and severity of lupus. After controlling for the possible confounding variables in conditional logistic regression models, the use of antimalarial drugs was assessed for its effects on the development of TEs in lupus patients. Results Fifty-four cases of TE were identified, and these were matched with 108 control subjects (lupus patients without TEs). Univariate analyses identified older age (odds ratio [OR] 1.04, 95% confidence interval [95%CI] 1.01,1.07) or being older than age 50 years (OR 3.5, 95% CI 1.4,8.6) and ever having hypertension (OR 2.5, 95% CI 1.0,5.8) as being associated with an increased risk of TEs, whereas use of antimalarial drugs (OR 0.31, 95% CI 0.13,0.71) was associated with a decreased risk of TEs. Separate analyses were done for arterial and venous TEs, which yielded similar results. In multivariate analyses, use of antimalarial drugs (OR 0.32, 95% CI 0.14,0.74) and older age (OR 1.04, 95% CI 1.01,1.07) were the only 2 variables that remained significant. Conclusion The results from this nested case,control study demonstrate that, after accounting for the effects of disease severity, disease duration, and calendar year, antimalarial drugs were found to be thromboprotective, being associated with a 68% reduction in the risk of all TEs, with a range of risk reduction of at least 26% up to as high as 86%. [source] Smoking and Risk of Premature Death among Middle-aged Japanese: Ten-year Follow-up of the Japan Public Health Center-based Prospective Study on Cancer and Cardiovascular Diseases (JPHC Study) Cohort ICANCER SCIENCE, Issue 1 2002Megumi Hara To update the evidence on the association between smoking and mortality, we analyzed data from a population-based prospective study in Japan. In total, 19 950 men and 21 534 women aged 40,59 who reported their smoking history and had no serious disease at baseline survey were followed. During 1990,1999, 1014 men and 500 women died. Smokers were associated with an unhealthy life-style. Relative risks (RRs) for selected cause of death due to smoking were slightly attenuated by adjusting for possible confounding factors. Age- and area-adjusted RRs of male current smokers compared with never smokers were 1.66 (95% confidence intervals (CI): 1.40, 1.95) for all causes, 1.69 (1.31, 2.18) for all cancers, 1.67 (1.20, 2.34) for all circulatory system disease, and 1.63 (1.24, 2.15) for other causes, while those of females were 2.03 (1.52, 2.73), 2.06 (1.35, 3.15), 2.99 (1.75, 5.11), 1.31 (0.69, 2.51), respectively. After adjusting for multivariate variables, the corresponding RRs of male smokers were 1.55 (1.29, 1.86), 1.61 (1.20, 2.15), 1.41 (0.97, 2.03), and 1.61 (1.17, 2.19), against 1.89 (1.36, 2.62), 1.83 (1.14, 2.95), 2.72 (1.45, 5.07), and 1.39 (0.71, 2.73) for females. Twenty-two percent of death from all causes, 25% of all cancer, and 17% of all circulatory system disease deaths, could be attributed to cigarette smoking in males, and 5%, 4%, and 11% in females, respectively. Cumulative dose as indicated by pack-years was clearly associated with cancer death. These findings provided information as to the quantitative risk for premature death due to smoking among middle-aged Japanese men and women, and showed that the elevated risk was not explained by the unhealthy lifestyle of smokers. [source] | ||||||||||