Igor Burstyn

Publications of Igor Burstyn

• Estimating the Extent and Distribution of New-Onset Adult Asthma in British Columbia Using Frequentist and Bayesian Approaches.

  Authors: Jeremy Beach, Igor Burstyn, Nicola Cherry

  The Annals of occupational hygiene. 02/2012;

  INTRODUCTION: We previously described a method to identify the incidence of new-onset adult asthma (NOAA) in Alberta by industry and occupation, utilizing Workers' Compensation Board (WCB) andINTRODUCTION: We previously described a method to identify the incidence of new-onset adult asthma (NOAA) in Alberta by industry and occupation, utilizing Workers' Compensation Board (WCB) and physician billing data. The aim of this study was to extend this method to data from British Columbia (BC) so as to compare the two provinces and to incorporate Bayesian methodology into estimates of risk. METHODS: WCB claims for any reason 1995-2004 were linked to physician billing data. NOAA was defined as a billing for asthma (ICD-9 493) in the 12 months before a WCB claim without asthma in the previous 3 years. Incidence was calculated by occupation and industry. In a matched case-referent analysis, associations with exposures were examined using an asthma-specific job exposure matrix (JEM). Posterior distributions from the Alberta analysis and estimated misclassification parameters were used as priors in the Bayesian analysis of the BC data. RESULTS: Among 1 118 239 eligible WCB claims the incidence of NOAA was 1.4%. Sixteen occupations and 44 industries had a significantly increased risk; six industries had a decreased risk. The JEM identified wood dust [odds ratio (OR) 1.55, 95% confidence interval (CI) 1.08-2.24] and animal antigens (OR 1.66, 95% CI 1.17-2.36) as related to an increased risk of NOAA. Exposure to isocyanates was associated with decreased risk (OR 0.57, 95% CI 0.39-0.85). Bayesian analyses taking account of exposure misclassification and informative priors resulted in posterior distributions of ORs with lower boundary of 95% credible intervals >1.00 for almost all exposures. CONCLUSIONS: The distribution of NOAA in BC appeared somewhat similar to that in Alberta, except for isocyanates. Bayesian analyses allowed incorporation of prior evidence into risk estimates, permitting reconsideration of the apparently protective effect of isocyanate exposure.

• The role of maternal smoking in effect of fetal growth restriction on poor scholastic achievement in elementary school.

  Authors: Igor Burstyn, Stefan Kuhle, Alexander C Allen, Paul Veugelers

  International journal of environmental research and public health. 02/2012; 9(2):408-20.

  Fetal growth restriction and maternal smoking during pregnancy are independently implicated in lowering intellectual attainment in children. We hypothesized that only reduction of fetal growth thatFetal growth restriction and maternal smoking during pregnancy are independently implicated in lowering intellectual attainment in children. We hypothesized that only reduction of fetal growth that is attributable to extrinsic causes (e.g., maternal smoking) affects intellectual development of a child. Cross-sectional survey of 3,739 students in Nova Scotia (Canada) in 2003 was linked with the perinatal database, parental interviews on socio-demographic factors and the performance on standardized tests when primarily 11-12 years of age, thereby forming a retrospective cohort. Data was analyzed using hierarchical logistic regression with correction for clustering of children within schools. The risk of poor test result among children born small-for-gestational-age (SGA) to mothers who smoked was 29.4%, higher than in any other strata of maternal smoking and fetal growth. The adjusted odds ratio among SGA children born to mothers who smoked was the only one elevated compared to children who were not growth restricted and born to mothers who did not smoke (17.0%, OR = 1.46, 95% CI 1.02, 2.09). Other perinatal, maternal and socio-demographic factors did not alter this pattern of effect modification. Heterogeneity of etiology of fetal growth restriction should be consider in studies that address examine its impact on health over life course.

• Authors' reply to Kundi's comments on de Vocht et al. "time trends (1998-2007) in brain cancer incidence rates in relation to mobile phone use in England"

  Authors: Frank de Vocht, Igor Burstyn, John W Cherrie

  Bioelectromagnetics. 05/2011;

• Bayesian inference of gene-environment interaction from incomplete data: what happens when information on environment is disjoint from data on gene and disease?

  Authors: Paul Gustafson, Igor Burstyn

  Statistics in medicine. 04/2011; 30(8):877-89.

  Inference in gene-environment studies can sometimes exploit the assumption of mendelian randomization that genotype and environmental exposure are independent in the population under study. Moreover,Inference in gene-environment studies can sometimes exploit the assumption of mendelian randomization that genotype and environmental exposure are independent in the population under study. Moreover, in some such problems it is reasonable to assume that the disease risk for subjects without environmental exposure will not vary with genotype. When both assumptions can be invoked, we consider the prospects for inferring the dependence of disease risk on genotype and environmental exposure (and particularly the extent of any gene-environment interaction), without detailed data on environmental exposure. The data structure envisioned involves data on disease and genotype jointly, but only external information about the distribution of the environmental exposure in the population. This is relevant as for many environmental exposures individual-level measurements are costly and/or highly error-prone. Working in the setting where all relevant variables are binary, we examine the extent to which such data are informative about the interaction, via determination of the large-sample limit of the posterior distribution. The ideas are illustrated using data from a case-control study for bladder cancer involving smoking behaviour and the NAT2 genotype.

• Perfluorinated acids and hypothyroxinemia in pregnant women.

  Authors: Emily Chan, Igor Burstyn, Nicola Cherry, Fiona Bamforth, Jonathan W Martin

  Environmental research. 02/2011; 111(4):559-64.

  Perfluorinated acids (PFAs) are prominent and widespread contaminants of human blood. In animal studies there is evidence that suggests certain PFAs can disrupt thyroid hormone homeostasis. APerfluorinated acids (PFAs) are prominent and widespread contaminants of human blood. In animal studies there is evidence that suggests certain PFAs can disrupt thyroid hormone homeostasis. A commonly reported condition in exposed animals is hypothyroxinemia, whereby serum free thyroxine (fT4) is decreased despite normal thyroid stimulating hormone (TSH) concentrations. We designed an individually matched case-control study to investigate whether exposure to perfluorooctanoate (PFOA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS) was associated with hypothyroxinemia in pregnant women from Edmonton, Alberta, Canada, in 2005-2006, who underwent a "triple screen" blood test at 15-20 weeks gestation as part of ante-natal care. Thyroid hormones, fT4 and TSH, were measured in serum from 974 women, and from these we measured PFAs in the sera of 96 hypothyroxinemic cases (normal TSH, the lowest 10th percentile of fT4) and 175 controls (normal TSH, fT4 between the 50th and 90th percentiles) matched on age and referring physician. Analyses by conditional logistic regression indicated that the concentrations of PFAs in this population were not associated with hypothyroxinemia among pregnant women. The current findings do not support a causal link between PFA exposure and maternal hypothyroxinemia in the studied population.

• Autism spectrum disorders and fetal hypoxia in a population-based cohort: accounting for missing exposures via Estimation-Maximization algorithm.

  Authors: Igor Burstyn, Xiaoming Wang, Yutaka Yasui, Fortune Sithole, Lonnie Zwaigenbaum

  BMC medical research methodology. 01/2011; 11:2.

  Autism spectrum disorders (ASD) are associated with complications of pregnancy that implicate fetal hypoxia (FH); the excess of ASD in male gender is poorly understood. We tested the hypothesis thatAutism spectrum disorders (ASD) are associated with complications of pregnancy that implicate fetal hypoxia (FH); the excess of ASD in male gender is poorly understood. We tested the hypothesis that risk of ASD is related to fetal hypoxia and investigated whether this effect is greater among males. Provincial delivery records (PDR) identified the cohort of all 218,890 singleton live births in the province of Alberta, Canada, between 01-01-98 and 12-31-04. These were followed-up for ASD via ICD-9 diagnostic codes assigned by physician billing until 03-31-08. Maternal and obstetric risk factors, including FH determined from blood tests of acidity (pH), were extracted from PDR. The binary FH status was missing in approximately half of subjects. Assuming that characteristics of mothers and pregnancies would be correlated with FH, we used an Estimation-Maximization algorithm to estimate HF-ASD association, allowing for both missing-at-random (MAR) and specific not-missing-at-random (NMAR) mechanisms. Data indicated that there was excess risk of ASD among males who were hypoxic at birth, not materially affected by adjustment for potential confounding due to birth year and socio-economic status: OR 1.13, 95%CI: 0.96, 1.33 (MAR assumption). Limiting analysis to full-term males, the adjusted OR under specific NMAR assumptions spanned 95%CI of 1.0 to 1.6. Our results are consistent with a weak effect of fetal hypoxia on risk of ASD among males. E-M algorithm is an efficient and flexible tool for modeling missing data in the studied setting.

• Time trends (1998-2007) in brain cancer incidence rates in relation to mobile phone use in England.

  Authors: Frank de Vocht, Igor Burstyn, John W Cherrie

  Bioelectromagnetics. 01/2011; 32(5):334-9.

  Mobile phone use in the United Kingdom and other countries has risen steeply since the early 1990's when the first digital mobile phones were introduced. There is an ongoing controversy about whetherMobile phone use in the United Kingdom and other countries has risen steeply since the early 1990's when the first digital mobile phones were introduced. There is an ongoing controversy about whether radio frequency (RF) exposure from mobile phones increases the risk of brain cancer. However, given the widespread use and nearly two decades elapsing since mobile phones were introduced, an association should have produced a noticeable increase in the incidence of brain cancer by now. Trends in rates of newly diagnosed brain cancer cases in England between 1998 and 2007 were examined. There were no time trends in overall incidence of brain cancers for either gender, or any specific age group. Systematic increases in rates for cancers of the temporal lobe in men (0.04 new cases/year) and women (0.02/year) were observed, along with decreases in the rates of cancers of the parietal lobe (-0.03/year), cerebrum (-0.02/year) and cerebellum (-0.01/year) in men only. The increased use of mobile phones between 1985 and 2003 has not led to a noticeable change in the incidence of brain cancer in England between 1998 and 2007. The observed increase in the rate of cancers in the temporal lobe, if caused by mobile phone use, would constitute <1 additional case per 100,000 people in that period. These data do not indicate a pressing need to implement a precautionary principle by means of population-wide interventions to reduce RF exposure from mobile phones.

• Bayesian adjustment for measurement error in continuous exposures in an individually matched case-control study.

  Authors: Gabriela Espino-Hernandez, Paul Gustafson, Igor Burstyn

  BMC medical research methodology. 01/2011; 11:67.

  In epidemiological studies explanatory variables are frequently subject to measurement error. The aim of this paper is to develop a Bayesian method to correct for measurement error in multipleIn epidemiological studies explanatory variables are frequently subject to measurement error. The aim of this paper is to develop a Bayesian method to correct for measurement error in multiple continuous exposures in individually matched case-control studies. This is a topic that has not been widely investigated. The new method is illustrated using data from an individually matched case-control study of the association between thyroid hormone levels during pregnancy and exposure to perfluorinated acids. The objective of the motivating study was to examine the risk of maternal hypothyroxinemia due to exposure to three perfluorinated acids measured on a continuous scale. Results from the proposed method are compared with those obtained from a naive analysis. Using a Bayesian approach, the developed method considers a classical measurement error model for the exposures, as well as the conditional logistic regression likelihood as the disease model, together with a random-effect exposure model. Proper and diffuse prior distributions are assigned, and results from a quality control experiment are used to estimate the perfluorinated acids' measurement error variability. As a result, posterior distributions and 95% credible intervals of the odds ratios are computed. A sensitivity analysis of method's performance in this particular application with different measurement error variability was performed. The proposed Bayesian method to correct for measurement error is feasible and can be implemented using statistical software. For the study on perfluorinated acids, a comparison of the inferences which are corrected for measurement error to those which ignore it indicates that little adjustment is manifested for the level of measurement error actually exhibited in the exposures. Nevertheless, a sensitivity analysis shows that more substantial adjustments arise if larger measurement errors are assumed. In individually matched case-control studies, the use of conditional logistic regression likelihood as a disease model in the presence of measurement error in multiple continuous exposures can be justified by having a random-effect exposure model. The proposed method can be successfully implemented in WinBUGS to correct individually matched case-control studies for several mismeasured continuous exposures under a classical measurement error model.

• Paid work, domestic work, and other determinants of pregnancy outcome in Ibadan, southwest Nigeria.

  Authors: Folashade O Omokhodion, Modupe O Onadeko, Olumuyiwa A Roberts, Jeremy R Beach, Igor Burstyn, Nicola M Cherry

  International journal of gynaecology and obstetrics: the official organ of the International Federation of Gynaecology and Obstetrics. 11/2010; 111(2):165-70.

  To identify the determinants of low birth weight (LBW), preterm birth, and stillbirth, and the factors associated with paid or domestic work that affected pregnancy outcome in Ibadan, Nigeria. ATo identify the determinants of low birth weight (LBW), preterm birth, and stillbirth, and the factors associated with paid or domestic work that affected pregnancy outcome in Ibadan, Nigeria. A cross-sectional study of women who delivered live or stillborn singleton neonates at 4 hospitals between February and June 2008. Participants were interviewed to obtain information on paid and domestic work activities during pregnancy, as well as obstetric history. Pregnancy outcomes and other clinical data were extracted from case notes. A total of 1504 mothers aged 20-45 years recorded 137 (9.1%) LBW neonates (<2.5 kg), 154 (10.2%) preterm deliveries (<37 weeks), and 56 (3.7%) stillbirths. There was no overall increased risk of these outcomes among working mothers. Multivariate logistic regression analysis of working mothers who had booked their deliveries revealed that lifting heavy objects at home, a clinical record of proteinuria, and hospital admission during pregnancy were associated with LBW. Predictors for preterm birth were self-reported exposure to vibration at work, nulliparity, history of preterm birth, 4 or fewer compared with more than 8 antenatal visits, and prolonged rupture of membranes. Predictors for stillbirth were low education and prolonged rupture of membranes. The results further support recommendations that physical exertion in paid and domestic work should be reduced during pregnancy.

• Maternal thyroid hormones in early pregnancy and risk of breech presentation.

  Authors: Mehrnaz Salehidobakhshari, Fiona Bamforth, Igor Burstyn

  Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstétrique et gynécologie du Canada : JOGC. 10/2010; 32(10):948-55.

  To evaluate the relationship between breech presentation at term (>/= 37 weeks of gestation) and maternal thyroid hormone activity in early gestation. We conducted a case-control study of thyroidTo evaluate the relationship between breech presentation at term (>/= 37 weeks of gestation) and maternal thyroid hormone activity in early gestation. We conducted a case-control study of thyroid hormone activity in 179 women who delivered a live term infant in breech presentation (cases) and 849 women who delivered a live term infant in cephalic presentation (control subjects). We used serum samples from prenatal screening at 15 to 16 weeks of gestation in 2006 and 2007 in Edmonton, Alberta. Maternal free thyroxin (fT4) and thyroid-stimulating hormone (TSH) were assayed. Logistic regression was used to estimate the odds of breech presentation in relation to the levels of thyroid hormones while controlling for potential confounders. There were no significant differences between the breech and cephalic groups when comparing fT4 levels (OR 0.94 per pmol/L; 95% CI 0.88 to 1.00) or TSH levels (OR 1.16 per mU/L; 95% CI 0.97 to 1.38) levels, after adjustment for all potential confounders. Segregating fT4 and TSH into quintiles showed the same pattern. Neither hypothyroidism nor hyperthyroidism was associated with risk of breech presentation. Our results provide evidence that maternal thyroid hormone levels at 15 to 16 weeks of gestation are not related to risk of breech presentation at birth in term infants.

• A case-control study of lung cancer nested in a cohort of European asphalt workers.

  Authors: Ann Olsson, Hans Kromhout, Michela Agostini, Johnni Hansen, Christina Funch Lassen, Christoffer Johansen, Kristina Kjaerheim, Sverre Langård, Isabelle Stücker, Wolfgang Ahrens, Thomas Behrens, Marja-Liisa Lindbohm, Pirjo Heikkilä, Dick Heederik, Lützen Portengen, Judith Shaham, Gilles Ferro, Frank de Vocht, Igor Burstyn, Paolo Boffetta

  Environmental health perspectives. 10/2010; 118(10):1418-24.

  We conducted a nested case-control study in a cohort of European asphalt workers in which an increase in lung cancer risk has been reported among workers exposed to airborne bitumen fume, althoughWe conducted a nested case-control study in a cohort of European asphalt workers in which an increase in lung cancer risk has been reported among workers exposed to airborne bitumen fume, although potential bias and confounding were not fully addressed. We investigated the contribution of exposure to bitumen, other occupational agents, and tobacco smoking to the risk of lung cancer among asphalt workers. Cases were cohort members in Denmark, Finland, France, Germany, the Netherlands, Norway, and Israel who had died of lung cancer between 1980 and the end of follow-up (2002-2005). Controls were individually matched in a 3:1 ratio to cases on year of birth and country. We derived exposure estimates for bitumen fume and condensate, organic vapor, and polycyclic aromatic hydrocarbons, as well as for asbestos, crystalline silica, diesel motor exhaust, and coal tar. Odds ratios (ORs) were calculated for ever-exposure, duration, average exposure, and cumulative exposure after adjusting for tobacco smoking and exposure to coal tar. A total of 433 cases and 1,253 controls were included in the analysis. The OR was 1.12 [95% confidence interval (CI), 0.84-1.49] for inhalation exposure to bitumen fume and 1.17 (95% CI, 0.88-1.56) for dermal exposure to bitumen condensate. No significant trend was observed between lung cancer risk and duration, average exposure, or cumulative exposure to bitumen fume or condensate. We found no consistent evidence of an association between indicators of either inhalation or dermal exposure to bitumen and lung cancer risk. A sizable proportion of the excess mortality from lung cancer relative to the general population observed in the earlier cohort phase is likely attributable to high tobacco consumption and possibly to coal tar exposure, whereas other occupational agents do not appear to play an important role.

• Exposure assessment for a nested case-control study of lung cancer among European asphalt workers.

  Authors: Michela Agostini, Gilles Ferro, Ann Olsson, Igor Burstyn, Frank De Vocht, Johnni Hansen, Christina Funch Lassen, Christoffer Johansen, Kristina Kjaerheim, Sverre Langard, Isabelle Stucker, Wolfgang Ahrens, Thomas Behrens, Marja-Liisa Lindbohm, Pirjo Heikkilä, Dick Heederik, Lützen Portengen, Judith Shaham, Paolo Boffetta, Hans Kromhout

  The Annals of occupational hygiene. 10/2010; 54(7):813-23.

  Development of a method for retrospective assessment of exposure to bitumen fume, bitumen condensate, organic vapour, polycyclic aromatic hydrocarbons, and co-exposures to known or suspected lungDevelopment of a method for retrospective assessment of exposure to bitumen fume, bitumen condensate, organic vapour, polycyclic aromatic hydrocarbons, and co-exposures to known or suspected lung carcinogens for a nested case-control study of lung cancer mortality among European asphalt workers. Company questionnaires and structured questionnaires used in interviews and industry-specific job-exposure matrices (JEMs) were elaborated and applied. Three sources of information were eventually used for exposure assessment and assignment: (i) data obtained in cohort phase, (ii) data from living subjects, next-of-kin, and fellow-workers questionnaires, and (iii) JEMs for bitumen exposure by inhalation and via skin and co-exposures to known or suspected lung carcinogens within and outside cohort companies. Inhalation and dermal exposure estimates for bitumen were adjusted for time trends, time spent in a job, and other determinants of exposure (e.g. oil gravel paving). Clothing patterns, personal protective devices, and personal hygiene were taken into consideration while estimating dermal exposure. Occupational exposures could be assessed for 433 cases and 1253 controls for relevant time periods. Only 43% of work histories were spent inside original asphalt and construction companies. A total of 95.8% of job periods in cohort companies could be coded at a more detailed level. Imputation of work time and 'hygienic behaviour' multipliers was needed for <10% of work history years. Overall, downward trends in exposure were present and differences existed between countries and companies. As expected, correlations were strongest (r > 0.7) among bitumen-related agents, while correlations between coal tar, bitumen-related agents, and established lung carcinogens were weaker (r < 0.4). A systematic and detailed approach was developed to estimate inhalation and dermal exposure for a nested case-control study among asphalt workers.

• A graphical tool to evaluate temporal coverage of occupational history by exposure measurements.

  Authors: Jelle Vlaanderen, Wouter Fransman, Brian Miller, Igor Burstyn, Dick Heederik, Fintan Hurley, Roel Vermeulen, Hans Kromhout

  Occupational and environmental medicine. 09/2010; 67(9):636-8.

  In occupational epidemiology, differences in the temporal coverage of the exposure history by available exposure measurement data may affect the uncertainty of exposure estimates. In the reporting ofIn occupational epidemiology, differences in the temporal coverage of the exposure history by available exposure measurement data may affect the uncertainty of exposure estimates. In the reporting of results of studies, greater attention should be paid to the extent to which exposure assessments require extrapolation outside the timeframe for which exposure measurements are available. We propose a simple graphical method that can be used to visualise the temporal coverage of exposure history with exposure measurements and the extent of temporal extrapolation needed. We construct a graph that displays the accumulated work history years for which exposure had to be assessed in each calendar year. Years for which exposure measurements were available are shaded. The proportion of work history years covered by exposure measurements and the proportion of work history years accrued before the first measurements are summarised. When available, the actual number of measurements available in each calendar year is shown. We demonstrate the application of the graphical tool in three nested case-control studies that reported on leukaemia in relation to low-level benzene exposures in the petroleum industry. Considerable differences in temporal coverage between the studies were illustrated, which may have resulted in differences in the reliability of the retrospective exposure estimates derived for these studies. We introduce a graphical tool for visualising the temporal coverage by available exposure measurement data in epidemiological studies and encourage others to use similar graphs to derive and share better qualitative insights into the uncertainty in exposure assessment.

• Obtaining compliance with occupational health and safety regulations: a multilevel study using self-determination theory.

  Authors: Igor Burstyn, Lorraine Jonasi, T Cameron Wild

  International journal of environmental health research. 08/2010; 20(4):271-87.

  It was hypothesized that occupational health and safety (OHS) inspectors who prefer to use autonomy supportive tactics to resolve workplace conflicts (e.g. providing rationale, choices) would be moreIt was hypothesized that occupational health and safety (OHS) inspectors who prefer to use autonomy supportive tactics to resolve workplace conflicts (e.g. providing rationale, choices) would be more effective in resolving industry non-compliance with OHS regulations, compared to inspectors who prefer to use coercive tactics (e.g. deadlines, pressure). Preferences for resolving work conflicts were collected from 39 Canadian OHS inspectors and were linked to administrative records documenting 17,960 industry inspection episodes and 29,451 compliance orders issued by those inspectors from 2003-2006. Multilevel Poisson and negative binomial regression models examined associations between inspector autonomy-supportiveness and compliance outcomes, adjusting for covariates at the inspector level (e.g. job experience, number of inspection episodes) and at the worksite level (e.g. workplace safety record). Relative to coercive inspectors, autonomy-supportive inspectors issued fewer severe compliance orders and achieved compliance after fewer worksite visits. Use of autonomy-supportive approaches may reduce exposure to preventable injuries at non-compliant worksites.

• Bias in the estimation of exposure effects with individual- or group-based exposure assessment.

  Authors: Hyang-Mi Kim, David Richardson, Dana Loomis, Martie Van Tongeren, Igor Burstyn

  Journal of exposure science & environmental epidemiology. 02/2010; 21(2):212-21.

  In this paper, we develop models of bias in estimates of exposure-disease associations for epidemiological studies that use group- and individual-based exposure assessments. In a study that uses aIn this paper, we develop models of bias in estimates of exposure-disease associations for epidemiological studies that use group- and individual-based exposure assessments. In a study that uses a group-based exposure assessment, individuals are grouped according to shared attributes, such as job title or work area, and assigned an exposure score, usually the mean of some concentration measurements made on samples drawn from the group. We considered bias in the estimation of exposure effects in the context of both linear and logistic regression disease models, and the classical measurement error in the exposure model. To understand group-based exposure assessment, we introduced a quasi-Berkson error structure that can be justified with a moderate number of exposure measurements from each group. In the quasi-Berkson error structure, the true value is equal to the observed one plus error, and the error is not independent of the observed value. The bias in estimates with individual-based assessment depends on all variance components in the exposure model and is smaller when the between-group and between-subject variances are large. In group-based exposure assessment, group means can be assumed to be either fixed or random effects. Regardless of this assumption, the behavior of estimates is similar: the estimates of regression coefficients were less attenuated with a large sample size used to estimate group means, when between-subject variability was small and the spread between group means was large. However, if groups are considered to be random effects, bias is present, even with large number of measurements from each group. This does not occur when group effects are treated as fixed. We illustrate these models in analyses of the associations between exposure to magnetic fields and cancer mortality among electric utility workers and respiratory symptoms due to carbon black.

• Antepartum risk score predicts adverse birth outcomes.

  Authors: Igor Burstyn

  Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstétrique et gynécologie du Canada : JOGC. 01/2010; 32(1):16-20.

  Standardized risk assessment plays an important role in providing medical care of uniform quality to pregnant women, even though it is not a substitute for clinical judgement. This study was designedStandardized risk assessment plays an important role in providing medical care of uniform quality to pregnant women, even though it is not a substitute for clinical judgement. This study was designed to determine whether the antepartum risk score currently used across Alberta is associated with neonatal morbidity and adverse pregnancy outcomes for singleton live births and to examine whether the current classification of "lower risk" pregnancies (score < 3) is justified. A retrospective study was conducted of the delivery records for a cohort of all live singleton births in Alberta from 2001 to 2005 that contained a completed antenatal risk assessment. Adverse neonatal condition or pregnancy outcome was assessed by Apgar score, transfer of the infant to a neonatal intensive care unit, "serious" resuscitation measures, preterm birth, and low birth weight. The population-attributable fraction of any of the adverse outcomes was calculated. All outcome measures except for NICU admissions were available for the entire 2001 to 2005 period (n = 191,686); NICU admissions were consistently recorded only from 2002 to 2005 (n = 154,924). The incidence of complications increased steadily as the risk score increased and increased more steeply above a score of 4. Approximately one third of the complications were associated with risk scores of between 2 and 6. The antepartum risk score currently used in Alberta is a useful tool for identifying women at higher risk of an adverse pregnancy outcome. Current categorization of pregnancies with an antepartum risk score of 2 as lower risk should be reconsidered in light of these findings.

• Historical "evidence" that electrification caused the 20th century epidemic of diseases of civilization and the ecological fallacy.

  Authors: Frank de Vocht, Igor Burstyn

  Medical hypotheses. 12/2009;

• The impact of isolated maternal hypothyroxinemia on perinatal morbidity.

  Authors: Michele P Hamm, Nicola M Cherry, Jonathan W Martin, Fiona Bamforth, Igor Burstyn

  Journal of obstetrics and gynaecology Canada : JOGC = Journal d'obstétrique et gynécologie du Canada : JOGC. 11/2009; 31(11):1015-21.

  To determine whether maternal hypothyroxinemia during early pregnancy is associated with adverse perinatal outcomes. Serum samples of a prospective cohort of 879 women collected at 15-16 weeks ofTo determine whether maternal hypothyroxinemia during early pregnancy is associated with adverse perinatal outcomes. Serum samples of a prospective cohort of 879 women collected at 15-16 weeks of pregnancy were analyzed for thyroid-stimulating hormone (TSH) and free thyroxine (T4) concentrations. Women with TSH levels within the normal reference range (0.15-4.0 mU/L) and free T4 levels below the 10th percentile of the sample (8.5 pmol/L) were classified as hypothyroxinemic and were compared with euthyroid women (who had normal TSH and free T4 levels). Thyroid hormone measures were linked to pregnancy outcomes, including small for gestational age (SGA), standardized birth weight z-score, preterm delivery, and Apgar score used as a measure of early neonatal morbidity. Among 89 hypothyroxinemic women, there was no evidence of an increased risk for fetal growth restriction, preterm birth, or low Apgar score. The relative risk of delivering an SGA infant was 0.38 (95% CI 0.11 to 1.33), the mean difference in birth weight z-score was 0.035 (95% CI -0.17 to 0.24), and the risk of preterm delivery was 0.79 (95% CI 0.38 to 1.67). None of the hypothyroxinemic women gave birth to an infant with a five-minute Apgar score <7. When free T4 levels were substituted for categories of thyroid hormone function, the pattern of results remained unaltered. Isolated maternal hypothyroxinemia was not observed to have any adverse effect on fetal growth or pregnancy outcome. This study does not provide evidence to support treatment of this condition to prevent fetal growth restriction or neonatal morbidity.

• Maternal exposure to perfluorinated acids and fetal growth.

  Authors: Michele P Hamm, Nicola M Cherry, Emily Chan, Jonathan W Martin, Igor Burstyn

  Journal of exposure science & environmental epidemiology. 10/2009;

  The widespread detection of perfluorinated acids (PFAs) in humans and known developmental toxicity in animals has raised concern about their potential effects on human reproductive health. OurThe widespread detection of perfluorinated acids (PFAs) in humans and known developmental toxicity in animals has raised concern about their potential effects on human reproductive health. Our objective was to determine whether increasing maternal exposure to PFAs is associated with adverse effects on fetal growth and length of gestation in women giving birth in Alberta, Canada. We examined the concentrations of perfluorooctanoic acid (PFOA), perfluorooctane sulfonate (PFOS), and perfluorohexane sulfonate (PFHxS) in a cohort of 252 pregnant women who gave birth to live singletons. Each of the women had undergone an early second trimester prenatal screen, and her serum was analyzed for PFA concentrations. Data on infant and maternal variables were collected from the delivery record completed at birth. Adjusted changes in birth weight per natural log (ng/ml) of PFOA (median 1.5 ng/ml), PFHxS (median 0.97 ng/ml), and PFOS (median 7.8 ng/ml) were -37.4 g (95% confidence interval (CI): -86.0 to 11.2 g), 21.9 g (-23.4 to 67.2 g), and 31.3 g (-43.3 to 105.9 g), respectively. Mean birth weight z-score, standardized for gestational age and gender, length of gestation, and risk of preterm birth did not appear to be influenced by maternal PFA exposure. When PFA concentrations were divided into tertiles, similar patterns were observed. These results suggest that maternal PFA exposure has no substantial effect on fetal weight and length of gestation at the concentrations observed in this population.Journal of Exposure Science and Environmental Epidemiology advance online publication, 28 October 2009; doi:10.1038/jes.2009.57.

• Data linkage to estimate the extent and distribution of occupational disease: new onset adult asthma in Alberta, Canada.

  Authors: Nicola Cherry, Jeremy Beach, Igor Burstyn, Xiangning Fan, Na Guo, Nitin Kapur

  American journal of industrial medicine. 09/2009;

  BACKGROUND: Although occupational asthma is a well recognized and preventable disease, the numbers of cases presenting for compensation may be far lower than the true incidence. METHODS: Workers'BACKGROUND: Although occupational asthma is a well recognized and preventable disease, the numbers of cases presenting for compensation may be far lower than the true incidence. METHODS: Workers' Compensation Board (WCB) claims for any reason 1995-2004 were linked to physician billing data. New onset adult asthma (NOAA) was defined as a billing for asthma (ICD-9 code of 493) in the 12 months prior to a WCB claim without asthma in the previous 3 years. Incidence was calculated by occupation, industry and, in a case-referent analysis, exposures estimated from an asthma specific job exposure matrix. RESULTS: There were 782,908 WCB eligible claims, with an incidence rate for NOAA of 1.6%: 23 occupations and 21 industries had a significantly increased risk. Isocyanates (OR 1.54: 95% CI 1.01-2.36) and exposure to mixed agricultural allergens (OR = 1.59: 95% CI 1.17-2.18) were related to NOAA overall, as were exposures to cleaning chemicals in men (OR = 1.91:95% CI 1.34-2.73). Estimates of the number of cases of occupational asthma suggested a range of 4% to about half for the proportion compensated. CONCLUSIONS: Data linkage of administrative records can demonstrate under-reporting of occupational asthma and indicate areas for prevention. Am. J. Ind. Med. (c) 2009 Wiley-Liss, Inc.