Search results for "Confounding Factors"
showing 10 items of 26 documents
Paracetamol and antibiotics in childhood and subsequent development of wheezing/asthma: association or causation?
2011
Background Several studies found an association between early administration of paracetamol and antibiotics and development of wheezing. This could be due to confounding: wheeze and asthmatic symptoms in early childhood are difficult to distinguish from respiratory tract infections that are widely treated with these drugs; in case of persistence of symptoms up to school age, this could explain the observed relationship. Methods We investigated the association between paracetamol and antibiotics use in the first year of life and wheezing phenotypes, i.e. wheezing starting in different time periods (early, persistent and late-onset) in the SIDRIA-2 study, a cross-sectional survey of 16,933 ch…
Coupled variable selection for regression modeling of complex treatment patterns in a clinical cancer registry.
2013
For determining a manageable set of covariates potentially influential with respect to a time-to-event endpoint, Cox proportional hazards models can be combined with variable selection techniques, such as stepwise forward selection or backward elimination based on p-values, or regularized regression techniques such as component-wise boosting. Cox regression models have also been adapted for dealing with more complex event patterns, for example, for competing risks settings with separate, cause-specific hazard models for each event type, or for determining the prognostic effect pattern of a variable over different landmark times, with one conditional survival model for each landmark. Motivat…
Inter‐individual variation of the urinary steroid profiles in Swedish and Norwegian athletes
2020
The steroidal module of the Athlete Biological Passport (ABP) aims to detect doping with endogenous steroids, e.g. testosterone (T), by longitudinally monitoring several biomarkers. These biomarkers are ratios combined of urinary concentrations of testosterone and metabolically related steroids. However, it is evident after five years of monitoring steroid passports, that there are large variations in the steroid ratios complicating its interpretation. In this study, we used over 11 000 urinary steroid profiles from Swedish and Norwegian athletes to determine both the inter‐ and intra‐individual variations of all steroids and ratios in the steroidal passport. Furthermore, we investigated if…
Exposure to UV radiation and risk of Hodgkin lymphoma: A pooled analysis
2013
Ultraviolet radiation (UVR) exposure has been inversely associated with Hodgkin lymphoma (HL) risk, but only inconsistently, only in a few studies, and without attention to HL heterogeneity. We conducted a pooled analysis of HL risk focusing on type and timing of UVR exposure and on disease subtypes by age, histology, and tumor-cell Epstein-Barr virus (EBV) status. Four case-control studies contributed 1320HLcasesand 6381 controls. We estimated lifetime, adulthood, and childhood UVR exposure and history of sunburn and sunlamp use. We used 2-stage estimation with mixed-effects models and weighted pooled effect estimates by inverse marginal variances. We observed statistically significant inv…
Neuropsychological testing of cognitive impairment in euthymic bipolar disorder: an individual patient data meta-analysis
2013
© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.
The MOAHLFA index of irritant sodium lauryl sulfate reactions: first results of a multicentre study on routine sodium lauryl sulfate patch testing
2004
In a multicentre study of the German Contact Dermatitis Research Group, sodium lauryl sulfate (SLS) 0.25% and 0.5% aq. has been added to routine allergen patch tests to assess its properties as a convenient diagnostic indicator of individual susceptibility to irritation at the time of patch testing. Previous studies indicated that irritant SLS reactivity may be related to individual factors such as age and sex. As these factors are, in turn, among the important predictors of contact allergy to many allergens, e.g. summarized in the 'MOAHLFA index', the impact of the MOAHLFA factors on irritant SLS patch test reactivity, and thus a potential for confounding, was assessed in the 5971 particip…
Host and environmental factors affecting the intestinal microbiota in chickens
2018
The initial development of intestinal microbiota in poultry plays an important role in production performance, overall health and resistance against microbial infections. Multiplexed sequencing of 16S ribosomal RNA gene amplicons is often used in studies, such as feed intervention or antimicrobial drug trials, to determine corresponding effects on the composition of intestinal microbiota. However, considerable variation of intestinal microbiota composition has been observed both within and across studies. Such variation may in part be attributed to technical factors, such as sampling procedures, sample storage, DNA extraction, the choice of PCR primers and corresponding region to be sequenc…
Occupational exposure to extremely low frequency electric and magnetic fields and Alzheimer disease: a meta-analysis
2008
Background Among potential environmental risk factors for Alzheimer disease (AD), occupational exposures have received some attention, including extremely low frequency electromagnetic fields (ELF-EMF). A systematic review and meta-analysis of published epidemiological studies on this subject was carried out. Methods The search was concluded in April 2006. Bibliographic databases consulted included PubMed, EMBASE, Cochrane Library and NIOSHTIC2. Pooled estimates were obtained using random-effects meta-analysis. Sources of heterogeneity between studies were explored, as was publication bias. Results Fourteen different studies (nine case-control and five cohort studies) accomplished inclusion…
Vitamin K antagonists' use and fracture risk: results from a systematic review and meta‐analysis
2015
Background: Although vitamin K antagonists (VKAs) lower serum values of bone deposition markers, the link with osteoporosis and fractures remains controversial. Objectives: To assess whether the use of VKAs is associated with an increased prevalence and/or incidence of osteoporosis, fractures, or lower bone mineral density (BMD) values. Methods: We conducted a systematic PubMed and EMBASE literature search until August 31, 2014, and a meta-analysis of cross-sectional and longitudinal studies investigating fractures and BMD, comparing patients treated with VKAs and healthy controls (HCs) or with patients with medical illness (medical controls, MCs). Standardized mean differences ± 95% and co…
Leukemia and Non-Hodgkin's Lymphoma in Childhood and Exposure to Pesticides: Results of a Register-based Case-Control Study in Germany
2001
Previous studies have suggested an association between exposure to pesticides and different types of childhood cancer. This paper presents results from a population-based case-control interview study of parents of children less than 15 years of age, which was conducted in the states of West Germany from 1993 to 1997. Cases were 1,184 children with leukemia, 234 with non-Hodgkin's lymphoma, and 940 with a solid tumor; 2,588 controls were also included. Parental occupational exposures were found to be related to childhood cancer regardless of the time period of exposure and the type of cancer. This finding might partially be explained by different recall of past exposures by the parents of ca…