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Exposure Status (exposure + status)
Selected AbstractsSimilar and functionally typical kinematic reaching parameters in 7- and 15-month-old in utero cocaine-exposed and unexposed infantsDEVELOPMENTAL PSYCHOBIOLOGY, Issue 3 2004E. Z. Tronick Abstract This study examined the effects of intrauterine cocaine exposure on the reaches of 19 exposed and 15 unexposed infants at 7 and 15 months using kinematic measures. Infants sat at a table and reached for a rattle, a toy doll, and a chair. Videotaped reaches were digitized using the Peak Performance system. Kinematic movement variables were extracted (e.g., reach duration, peak velocity, movement units, path length) and ratios computed (e.g., path length divided by number of movement units). Regardless of exposure status, reaches of older infants were faster, more direct, had fewer movement units, and covered more distance with the first movement unit. Exposed infants covered more distance per movement unit than unexposed infants, but there were no other significant differences. Reaches of exposed and unexposed infants were essentially similar. Importantly, reach parameters for these high-risk infants were similar to reach parameters for infants at lower social and biological risk. © 2004 Wiley Periodicals, Inc. Dev Psychobiol 44: 168,175, 2004. [source] Analytical ecological epidemiology: exposure,response relations in spatially stratified time seriesENVIRONMETRICS, Issue 6 2009Hagen Scherb Abstract An important task of environmental research is the investigation of a possible causal relationship between exposure and the frequency of a biologic trait. Major industrial accidents provide examples where the exposure status of large populations may change considerably within relatively short time intervals of days or weeks (e.g. Seveso herbicide plant explosion, Chernobyl Nuclear Power Plant catastrophe). Therefore, purely temporal change-points may be tested in time series of appropriate public health indicators (e.g. mortality, morbidity, sex ratio at birth). If, in addition, the spatial contamination is strong and variable enough and can be identified with sufficient precision at the level of regional units (e.g. districts), then a spatial-temporal approach makes sense. This essentially means that a global time trend model is adjusted for region-specific trend functions, allowing for local or global temporal jumps or broken sticks (change-points) at certain points in time. The local jump heights may be tested for associations with local exposure (exposure,response relation), and all other characteristics in the data that vary with locality and in time are automatically accounted for, thus minimizing confounding. Spatial-temporal approaches may help to strengthen the evidence of possible causal relationships. As an example, the human sex ratio at birth in several European countries before and after the Chernobyl Nuclear Power Plant accident was investigated. A long-term chronic impact of radioactive fallout on the secondary sex ratio has been found. Copyright © 2008 John Wiley & Sons, Ltd. [source] Evaluating uses of data mining techniques in propensity score estimation: a simulation study,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 6 2008DrPH, Soko Setoguchi MD Abstract Background In propensity score modeling, it is a standard practice to optimize the prediction of exposure status based on the covariate information. In a simulation study, we examined in what situations analyses based on various types of exposure propensity score (EPS) models using data mining techniques such as recursive partitioning (RP) and neural networks (NN) produce unbiased and/or efficient results. Method We simulated data for a hypothetical cohort study (n,=,2000) with a binary exposure/outcome and 10 binary/continuous covariates with seven scenarios differing by non-linear and/or non-additive associations between exposure and covariates. EPS models used logistic regression (LR) (all possible main effects), RP1 (without pruning), RP2 (with pruning), and NN. We calculated c-statistics (C), standard errors (SE), and bias of exposure-effect estimates from outcome models for the PS-matched dataset. Results Data mining techniques yielded higher C than LR (mean: NN, 0.86; RPI, 0.79; RP2, 0.72; and LR, 0.76). SE tended to be greater in models with higher C. Overall bias was small for each strategy, although NN estimates tended to be the least biased. C was not correlated with the magnitude of bias (correlation coefficient [COR],=,,0.3, p,=,0.1) but increased SE (COR,=,0.7, p,<,0.001). Conclusions Effect estimates from EPS models by simple LR were generally robust. NN models generally provided the least numerically biased estimates. C was not associated with the magnitude of bias but was with the increased SE. Copyright © 2008 John Wiley & Sons, Ltd. [source] Using prescription registries to define continuous drug use: how to fill gaps between prescriptions,PHARMACOEPIDEMIOLOGY AND DRUG SAFETY, Issue 4 2008Lars Hougaard Nielsen MSc Abstract Pharmacoepidemiological studies often use prescription registries to assess patients' drug episodes. The databases usually provide information on the date of the redemption of the prescription as well as on the dispensed amount, and this allows us to define episodes of drug use. However, when patients take less medication than prescribed, apparent gaps between prescriptions occur, and most studies handle this issue by allowing for small gaps when defining continuous drug use. This paper argues that it becomes crucial whether gaps are ,filled' prospectively or retrospectively. In the latter case the inferred exposure status depends on the patient's future dispensing behaviour and this can lead to severe bias in the findings of the study. In this paper we investigate this potential bias in a study of the risk of acute myocardial infarction (AMI) for women using hormone therapy (HT), and we show that the retrospective exposure definition introduces an artificially protective effect of HT. Copyright © 2008 John Wiley & Sons, Ltd. [source] Morbidity in former sawmill workers exposed to pentachlorophenol (PCP): A cross-sectional study in New ZealandAMERICAN JOURNAL OF INDUSTRIAL MEDICINE, Issue 4 2009David McLean PhD Abstract Background From 1950 to 1990 pentachlorophenol (PCP) was used widely in the New Zealand sawmill industry, and persistent claims of long-term health effects have been made. Methods We surveyed surviving members of a cohort enumerated to study mortality in sawmill workers employed from 1970 to 1990. Estimates of historical exposure were based on job titles held, using the results of a PCP biomonitoring survey conducted in the 1980s. The survey involved interviews and clinical examinations, with interviewers and examiners blinded to exposure status. Results Of the 293 participants 177 had not been exposed, and of the 116 exposed all but 10% had low or short-term PCP exposure. Nevertheless, a number of significant associations between PCP exposure and the prevalence of various symptoms were observed including associations between: (i) exposure levels and self-reported tuberculosis, pleurisy or pneumonia (P,<,0.01) and a deficit in cranial nerve function (P,=,0.04); (ii) duration of employment and thyroid disorders (P,=,0.04), and neuropsychological symptoms including often going back to check things (P,=,0.04), low libido (P,=,0.02) and heart palpitations (P,=,0.02), and a strong dose,response trend for frequent mood changes without cause (P,<,0.01); and (iii) cumulative exposure and frequent mood changes without cause (P,=,0.02), low libido (P,=,0.04), and in the overall number of neuropsychological symptoms reported (P,=,0.03). Conclusions PCP exposure was associated with a number of physical and neuropsychological health effects that persisted long after exposure had ceased. Am. J. Ind. Med. 52:271,281, 2009. © 2009 Wiley-Liss, Inc. [source] Sexual Function in F-111 Maintenance Workers: The Study of Health Outcomes in Aircraft Maintenance PersonnelTHE JOURNAL OF SEXUAL MEDICINE, Issue 6 2009Anthony Brown MPH ABSTRACT Introduction., In Australia, four formal F-111 fuel tank deseal/reseal (DSRS) repair programs were implemented over more than two decades, each involving different processes and using a range of hazardous substances. However, health concerns were raised by a number of workers. The "Study of Health Outcomes in Aircraft Maintenance Personnel" was commissioned by the Australian Department of Defence to investigate potential adverse health outcomes as a result of being involved in the deseal/reseal processes. Aim., To compare measures of sexual function in F-111 aircraft fuel tank DSRS maintenance workers, against two appropriate comparison groups. Methods., Exposed and comparison participants completed a postal questionnaire which included general questions of health and health behavior, and two specific questions on sexual functioning. They also completed the International Index of Erectile Function (IIEF) questionnaire. Logistic regression was used to explore exposure status and outcome while adjusting for potential confounders. Main Outcome Measures., The three outcomes of interest for this study were the proportion of participants with erectile dysfunction (ED) according to the IIEF, the proportion with self-reported loss of interest in sex, and the proportion with self-reported problems with sexual functioning. Results., Compared with each of the comparison groups, a larger proportion of the exposed group reported sexual problems and were classified as having ED according to the IIEF. In logistic regression, the odds of all three outcomes were higher for exposed participants relative to each comparison group and after adjustment for potentially confounding variables including anxiety and depression. Conclusions., There was a consistent problem with sexual functioning in the exposed group that is not explained by anxiety and depression, and it appears related to DSRS activities. Brown A, Gibson R, Tavener M, Guest M, D'Este C, Byles J, Attia J, Horsley K, Harrex W, and Ross J. Sexual function in F-111 maintenance workers: The study of health outcomes in aircraft maintenance personnel. J Sex Med 2009;6:1569,1578. [source] Maternal sleep deprivation is a risk factor for small for gestational age: A cohort studyAUSTRALIAN AND NEW ZEALAND JOURNAL OF OBSTETRICS AND GYNAECOLOGY, Issue 4 2009Chrishantha ABEYSENA Aims: To determine trimester-specific risk factors for small-for-gestational-age (SGA) infants. Methods: A population-based prospective cohort study was conducted in Sri Lanka from May 2001 to April 2002. Pregnant women were recruited on or before 16 weeks of gestation and followed up until delivery. The sample size was 690. Trimester-specific exposure status and potential confounding factors were gathered on average at 12th, 28th and 36th weeks of gestation. SGA was assessed using customised birth centile charts. Multiple logistic regression was applied, and the results were expressed as odds ratios (OR) and 95% confidence intervals (95%CI). Results: The risk factors for SGA less than 5th centile were shift work and exposure to physical and chemical hazards during 2nd and 3rd trimesters (OR 4.20, 95%CI 1.10,16.0), sleeping for less than or equal to 8 h during 2nd or 3rd or both trimesters (OR 2.23, 95%CI 1.08,4.59), walking for less than or equal to 2.5 h per day (OR 2.66, 95%CI 1.12,6.31) and alcohol consumption during the 3rd trimester (OR 14.5, 95%CI 2.23,94.7). Poor weekly gestational weight gain was significantly associated with both SGA < 10th and < 5th centiles. None of the other factors became significant for SGA < 10th centile. Conclusions: Risk factors for SGA less than 5th centile were sleep deprivation and shift work and exposure to physical and chemical hazards during 2nd and 3rd trimesters, less walking hours and alcohol consumption during 3rd trimester. Poor weekly gestational weight gain may be considered as a predictor of delivering an SGA infant. [source] Matched Case,Control Data Analysis with Selection BiasBIOMETRICS, Issue 4 2001I-Feng Lin Summary. Case-control studies offer a rapid and efficient way to evaluate hypotheses. On the other hand, proper selection of the controls is challenging, and the potential for selection bias is a major weakness. Valid inferences about parameters of interest cannot be drawn if selection bias exists. Furthermore, the selection bias is difficult to evaluate. Even in situations where selection bias can be estimated, few methods are available. In the matched case-control Northern Manhattan Stroke Study (NOMASS), stroke-free controls are sampled in two stages. First, a telephone survey ascertains demographic and exposure status from a large random sample. Then, in an in-person interview, detailed information is collected for the selected controls to be used in a matched case,control study. The telephone survey data provides information about the selection probability and the potential selection bias. In this article, we propose bias-corrected estimators in a case-control study using a joint estimating equation approach. The proposed bias-corrected estimate and its standard error can be easily obtained by standard statistical software. [source] | |||||||||||||