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Results for “Effect Modifier, Epidemiologic”

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PubMed2004

Do socioeconomic characteristics modify the short term association between air pollution and mortality? Evidence from a zonal time series in Hamilton, Canada.

STUDY OBJECTIVE: To assess the short term association between air pollution and mortality in different zones of an industrial city. An intra-urban study design is used to test the hypothesis that socioeconomic characteristics modify the acute health effects of ambient air pollution exposure. DESIGN: The City of Hamilton, Canada, was divided into five zones based on proximity to fixed site air pollution monitors. Within each zone, daily counts of non-trauma mortality and air pollution estimates were combined. Generalised linear models (GLMs) were used to test mortality associations with sulphur dioxide (SO(2)) and with particulate air pollution measured by the coefficient of haze (CoH). MAIN RESULTS: Increased mortality was associated with air pollution exposure in a citywide model and in intra-urban zones with lower socioeconomic characteristics. Low educational attainment and high manufacturing employment in the zones significantly and positively modified the acute mortality effects of air pollution exposure. DISCUSSION: Three possible explanations are proposed for the observed effect modification by education and manufacturing: (1) those in manufacturing receive higher workplace exposures that combine with ambient exposures to produce larger health effects; (2) persons with lower education are less mobile and experience less exposure measurement error, which reduces bias toward the null; or (3) manufacturing and education proxy for many social variables representing material deprivation, and poor material conditions increase susceptibility to health risks from air pollution.

Adult↗
PubMed2004

Influence of socioeconomic conditions on air pollution adverse health effects in elderly people: an analysis of six regions in São Paulo, Brazil.

STUDY OBJECTIVE: To evaluate if the effects of particulate matter (PM(10)) on respiratory mortality of elderly people are affected by socioeconomic status. DESIGN: Time series studies. The daily number of elderly respiratory deaths were modelled in generalised linear Poisson regression models controlling for long term trend, weather, and day of the week, from January 1997 to December 1999, in six different regions of São Paulo City, Brazil. The regions were defined according to the proximity of air pollution monitoring stations. Three socioeconomic indicators were used: college education, monthly income, and housing. MAIN RESULTS: For a 10 micro g/m(3) increase in PM(10), the percentage increase in respiratory mortality varied from 1.4% (95% CI 5.9 to 8.7) to 14.2% (95% CI 0.4 to 28.0). The overall percentage increase in the six regions was 5.4% (95% CI 2.3 to 8.6). The effect of PM(10) was negatively correlated with both percentage of people with college education and high family income, and it was positively associated with the percentage of people living in slums. CONCLUSIONS: These results suggest that socioeconomic deprivation represents an effect modifier of the association between air pollution and respiratory deaths.

Aged↗
PubMed2006

NO2 and children's respiratory symptoms in the PATY study.

OBJECTIVES: NO2)is a major urban air pollutant. Previously reported associations between ambient NO2)and children's respiratory health have been inconsistent, and independent effects of correlated pollutants hard to assess. The authors examined effects of NO2 on a spectrum of 11 respiratory symptoms, controlling for PM10 and SO2, using a large pooled dataset. METHODS: Cross sectional studies were conducted in Russia, Austria, Italy, Switzerland, and the Netherlands, during 1993-99, contributing in total 23 955 children. Study-specific odds ratios for associations with ambient NO2 are estimated using logistic regressions with area-level random effects. Heterogeneity between study-specific results, and mean estimates (allowing for heterogeneity) are calculated. RESULTS: Long term average NO2 concentrations were unrelated to prevalences of bronchitis or asthma. Associations were found for sensitivity to inhaled allergens and allergy to pets, with mean odds ratios around 1.14 per 10 microg/m3 NO2. SO2 had little confounding effect, but an initial association between NO2 and morning cough was reduced after controlling for PM10. Associations with reported allergy were not reduced by adjustment for the other pollutants. Odds ratios for allergic symptoms tended to be higher for the 9-12 year old children compared with the 6-8 year old children. CONCLUSIONS: Evidence for associations between NO2 and respiratory symptoms was robust only for inhalation allergies. NO2 most likely is acting as an indicator of traffic related air pollutants, though its direct effect cannot be ruled out. This remains important, as policies to reduce traffic related air pollution will not result in rapid reductions.

Air Pollutants↗
PubMed2007

Mediation analysis.

Mediating variables are prominent in psychological theory and research. A mediating variable transmits the effect of an independent variable on a dependent variable. Differences between mediating variables and confounders, moderators, and covariates are outlined. Statistical methods to assess mediation and modern comprehensive approaches are described. Future directions for mediation analysis are discussed.

Analysis of Variance↗
PubMed2000

Multilevel analysis in public health research.

Over the past few years there has been growing interest in considering factors defined at multiple levels in public health research. Multilevel analysis has emerged as one analytical strategy that may partly address this need, by allowing the simultaneous examination of group-level and individual-level factors. This paper reviews the rationale for using multilevel analysis in public health research, summarizes the statistical methodology, and highlights some of the research questions that have been addressed using these methods. The advantages and disadvantages of multilevel analysis compared with standard methods are reviewed. The use of multilevel analysis raises theoretical and methodological issues related to the theoretical model being tested, the conceptual distinction between group- and individual-level variables, the ability to differentiate "independent" effects, the reciprocal relationships between factors at different levels, and the increased complexity that these models imply. The potentialities and limitations of multilevel analysis, within the broader context of understanding the role of factors defined at multiple levels in shaping health outcomes, are discussed.

Analysis of Variance↗
PubMedDate not supplied

Metabolic control as a modifier of the association between salivary factors and dental caries among diabetic patients.

The aim here was to analyze the role of metabolic control as a modifier of the association of salivary factors with dental caries among diabetic patients. Cross-sectional data were gathered from 149 insulin-dependent diabetes mellitus patients by means of clinical examination, a quantitative questionnaire and patient records. Dental caries was measured as the number of decayed surfaces. The data were analyzed using negative binomial regression models. HbA1(c) level appeared not to be associated with dental caries. Of the salivary factors, only high levels of mutans streptococci (MS) and lactobacilli were associated with dental caries. Among the subjects with HbA1(c) > or =8.5, the presence of dental caries was more distinctly associated with higher levels of MS (RR = 3.86, CI: 1.39-11.96) and lactobacilli (RR = 3.59, CI: 1.44-9.33) compared to those with HbA1(c)<8.5. It can be concluded that poor glycemic control strengthens the positive association of MS and lactobacilli with dental caries.

Adult↗
PubMed1997

Lower respiratory illness, recurrent wheezing, and day care attendance.

We prospectively assessed the relations between various characteristics of day care and lower respiratory illness (LRI) in a cohort of 1,268 Minnesotan children, born between October 1989 and January 1991 and followed to 2 yr of age. Information on LRI was abstracted from medical records and data on day care use, respiratory symptoms, and physician diagnosis of asthma were obtained from questionnaires. We identified a subgroup of 60 children with recurrent wheezing illnesses. The LRI rate ratio for day care attendance was 2.0 (95% confidence interval = 1.7, 2.2). Rate ratios were similar regardless of the day care setting, number of other children present, or the number of hours spent in day care. A parental history of asthma further increased the rate ratio for day care attendance. Day care attendance was associated with a threefold risk of having recurrent wheezing illnesses. We conclude that day care attendance is an important risk factor for LRI in young children, and for recurrent wheezing illnesses.

Child Day Care Centers↗
PubMed1999

Memory impairment in schizophrenia: a meta-analysis.

OBJECTIVE: Memory impairment is well documented in schizophrenia. Less is known, however, about the exact magnitude, pattern, and extent of the impairment. The effect of potential moderator variables, such as medication status and duration of illness, is also unclear. In this article, the authors presented meta-analyses of the published literature on recall and recognition memory performance between patients with schizophrenia and normal comparison subjects. METHOD: Meta-analyses were conducted on 70 studies that reported measures of long-term memory (free recall, cued recall, and recognition of verbal and nonverbal material) and short-term memory (digit span). Tests of categorical models were used in analyses of potential moderators (clinical variables and study characteristics). RESULTS: The findings revealed a significant and stable association between schizophrenia and memory impairment. The composite effect size for recall performance was large. Recognition showed less, but still significant, impairment. The magnitude of memory impairment was not affected by age, medication, duration of illness, patient status, severity of psychopathology, or positive symptoms. Negative symptoms showed a small but significant relation with memory impairment. CONCLUSIONS: This meta-analysis documented significant memory impairment in schizophrenia. The impairment was stable, wide ranging, and not substantially affected by potential moderating factors such as severity of psychopathology and duration of illness.

Comorbidity↗
PubMed2003

The fundamental attribution error in detecting deception: the boy-who-cried-wolf effect.

Most people are unable to detect accurately when others are lying. Many explanations for this inability have been suggested but the cognitive heuristics involved in lie detection have received little attention. The present study offers evidence from two experiments, based on two different groups of observers, judging two different kinds of lies, presented in two different testing situations, that the fundamental attribution error significantly undermines the ability to detect honesty and deception accurately. Trait judgments of trustworthiness were highly correlated with state judgments of truthfulness, leading, as predicted, to positive correlations with honest detection accuracy and negative correlations with deception detection accuracy. More accurate lie detectors were significantly more likely than less accurate lie detectors to separate state and trait judgments of honesty. The effect of other biases, such as the halo effect and the truthfulness bias, also are examined. Implications for future research and practice are discussed.

Adolescent↗
PubMed1998

Using outcomes to make inferences about nursing home quality.

Recent concerns about containing the growth of public expenditures on nursing home care and the development of prospective and casemix reimbursement systems with incentives for cost containment have increased the importance of monitoring quality in nursing homes. The current view is that quality assurance systems should include more outcome measures to improve quality. This article discusses why it is difficult to develop facility-level outcome measures that can be used to evaluate and compare the quality of care of nursing homes. The article places the current interest in outcomes measures in its historical policy context and reviews important conceptual and methodological issues associated with outcome-based quality assessment. The authors discuss the difficulty in isolating the facility effect when studying nursing home outcomes and implications of using different estimation approaches. In conclusion, they discuss the need to integrate research with outcome-based quality assurance systems to allow ongoing evaluation and quality improvement.

Bias↗
PubMed2002

Addressing self-selection bias in quasi-experimental evaluations of whole-school reform. A comparison of methods.

This article discusses potential sources of self-selection bias in quasi-experimental evaluations of whole-school reform models and considers how individual student-level data might be used to provide valid impact estimates. Although repeated pretreatment and posttreatment measures of student performance can provide unbiased estimates under relatively weak assumptions, such data are difficult to obtain. The article develops an instrumental variable strategy that can be used to improve on common value-added estimators when only posttreatment measures of performance are available. Using data from New York City, the author shows that the instrumental variable strategy can provide estimates of model impacts similar to those provided by a difference-in-differences estimator provided that appropriate instruments are used.

Bias↗
PubMed2001

Statistical power for nonequivalent pretest-posttest designs. The impact of change-score versus ANCOVA models.

Nonequivalent controlled pretest-posttest designs are central to evaluation science, yet no practical and unified approach for estimating power in the two most widely used analytic approaches to these designs exists. This article fills the gap by presenting and comparing useful, unified power formulas for ANCOVA and change-score analyses, indicating the implications of each on sample-size requirements. The authors close with practical recommendations for evaluators. Mathematical details and a simple spreadsheet approach are included in appendices.

Analysis of Variance↗
PubMed1999

Multilevel mediation modeling in group-based intervention studies.

This article proposes and evaluates a method to test for mediation in multilevel data sets formed when an intervention administered to intact groups is designed to produce change in individual mediator and outcome variables. Simulated data of this form were used to compare ordinary least squares (OLS) and two multilevel estimators of the mediated effect. OLS and multilevel standard error approximations were also evaluated and recommendations given for optimal estimator choice. These methods were applied to data from an existing substance use intervention to show the impact multilevel mediation modeling can have on the conclusions drawn from real-world evaluation studies.

Analysis of Variance↗
PubMed1999

Using cluster random assignment to measure program impacts. Statistical implications for the evaluation of education programs.

This article explores the possibility of randomly assigning groups (or clusters) of individuals to a program or a control group to estimate the impacts of programs designed to affect whole groups. This cluster assignment approach maintains the primary strength of random assignment--the provision of unbiased impact estimates--but has less statistical power than random assignment of individuals, which usually is not possible for programs focused on whole groups. To explore the statistical implications of cluster assignment, the authors (a) outline the issues involved, (b) present an analytic framework for studying these issues, and (c) apply this framework to assess the potential for using the approach to evaluate education programs targeted on whole schools. The findings suggest that cluster assignment of schools holds some promise for estimating the impacts of education programs when it is possible to control for the average performance of past student cohorts or the past performance of individual students.

Bias↗
PubMed1999

Modeling the individual determinants of research utilization.

Despite more than two decades of investigation, our accumulated knowledge about what influences nurses' use of research is underdeveloped. This study's objectives were to develop and test a series of structural equation models that included individual factors believed to influence research utilization. Estimates of the models were obtained using maximum likelihood estimation. Model fit was assessed by examining chi-square, the adjusted goodness of fit index, and the standardized residuals. Within a simple model that permitted only direct effects and controlled for instrumental, conceptual, and persuasive research utilization, 3 of 26 concepts exerted significant effects on research utilization. These were a positive attitude toward research, belief suspension, and in-services attended. These results support the assertion that our descriptive body of research on the determinants of research utilization is underdeveloped, limiting our ability to design and test effective strategies to increase the use of research findings in nursing practice.

Attitude of Health Personnel↗