Search results for " Bias"
showing 10 items of 437 documents
Isotope fractionation of zinc in the paddy rice soil-water environment and the role of 2’deoxymugineic acid (DMA) as zincophore under Zn limiting con…
2021
Non-traditional stable isotope systems are increasingly used to study micronutrient cycling and acquisition in terrestrial ecosystems. We previously proposed for zinc (Zn) a conceptual model linking observed isotope signatures and fractionations to biogeochemical processes occurring in the rice soil environment and we suggested that 2’deoxymugineic acid (DMA) could play an important role for rice during the acquisition of Zn when grown under Zn limiting conditions. This proposition was sustained by the extent and direction of isotope fractionation observed during the complexation of Zn with DMA synthesised in our laboratory. Here we report a new set of experimental data from field and labor…
Combined associations of body weight and lifestyle factors with all cause and cause specific mortality in men and women: prospective cohort study
2016
Objective To evaluate the combined associations of diet, physical activity, moderate alcohol consumption, and smoking with body weight on risk of all cause and cause specific mortality. Design Longitudinal study with up to 32 years of follow-up. Setting Nurses’ Health Study (1980-2012) and Health Professionals Follow-up Study (1986-2012). Participants 74 582 women from the Nurses’ Health Study and 39 284 men from the Health Professionals Follow-up Study who were free from cardiovascular disease and cancer at baseline. Main outcome measures Exposures included body mass index (BMI), score on the alternate healthy eating index, level of physical activity, smoking habits, and alcohol drink…
Effects of 32-year leisure time physical activity discordance in twin pairs on health (TWINACTIVE study): aims, design and results for physical fitne…
2009
AbstractThe physically active lifestyle is associated with low future morbidity and mortality, but the causality between physical activity and health is not always clear. As some inherited biological characteristics and childhood experiences may cause selection bias in observational studies, we sought to take them into account by identifying 16 twin pairs (7 MZ, 9 DZ, mean age 60 years) discordant for leisure time physical activity habits for thirty years. We conducted detailed health-related examinations among these twin pairs. Our main aims were to study the effects of physical activity and genes on fitness and body composition, with special reference to body fat compartments, metabolic s…
Relationship between depression and frailty in older adults: A systematic review and meta-analysis
2017
Aim Depression and frailty are prevalent and burdensome in older age. However, the relationships between these entities are unclear and no quantitative meta- analysis exists. We conducted a systematic review and meta-analysis to investigate the associations between depression and frailty. Methods Two authors searched major electronic databases from inception until November-2016 for cross-sectional/longitudinal studies investigating depression and frailty. The strength of the reciprocal associations between frailty and depression was assessed through odds ratios (ORs) adjusted for potential confounders. Results From 2306 non duplicated hits, 24 studies were included. The overall prevalence o…
Modifiable Lifestyle Factors and Cognitive Function in Older People: A Cross-Sectional Observational Study
2019
Background: The development of evidence-based interventions for delaying or preventing cognitive impairment is an important challenge. Most previous studies using self-report questionnaires face problems with reliability and consistency due to recall bias or misclassification among older people. Therefore, objective measurement of lifestyle components is needed to confirm the relationships between lifestyle factors and cognitive function. Aims: The current study examined the relationship between lifestyle factors collected with wearable sensors and cognitive function among community-dwelling older people using machine learning. Methods: In total, 855 participants (mean age: 73.8 years) wore…
Nonparticipation Selection Bias in the MOBI-Kids Study.
2018
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Assessing physical performance and physical activity in large population-based aging studies: home-based assessments or visits to the research center?
2019
Abstract Background The current study aims to compare correlations between a range of measures of physical performance and physical activity assessing the same underlying construct in different settings, that is, in a home versus a highly standardized setting of the research center or accelerometer recording. We also evaluated the selective attrition of participants related to these different settings and how selective attrition affects the associations between variables and indicators of health, functioning and overall activity. Methods Cross-sectional analyses comprising population-based samples of people aged 75, 80, and 85 years living independently in Jyväskylä, Finland. The AGNES stud…
Intercomparison and quality assessment of MERIS, MODIS and SEVIRI FAPAR products over the Iberian Peninsula
2013
Abstract The fraction of absorbed photosynthetically active radiation (FAPAR) is a key variable in productivity and carbon cycle models. The variety of available FAPAR satellite products from different space agencies leads to the necessity of assessing the existing differences between them before using into models. Discrepancies of four FAPAR products derived from MODIS, SEVIRI and MERIS (TOAVEG and MGVI algorithms), covering the Iberian Peninsula from July 2006 to June 2007 are here analyzed. The assessment is based on an intercomparison involving the spatial and temporal consistency between products and a statistical analysis across land cover types. In general, significant differences ar…
Reporting heterogeneity in health: an extended latent class approach
2012
This article explores how individual socio-economic characteristics affect unobserved heterogeneity in self-reporting behaviour and health production using a multivariate finite mixture model. Results show a positive relationship between objective and subjective observable health indicators and true health and support the existence of self-reporting bias related to socio-economic characteristics and individual life styles.
Avoiding Bias in Observational Studies
2009
Background Many questions in human health research can only be answered with observational studies. In contrast to controlled experiments or well-planned, experimental randomized clinical trials, observational studies are subject to a number of potential problems that may bias their results.