A hybrid expert approach for retrospective assessment of occupational exposures in a population-based case-control study of cancer.

BACKGROUND: While the expert-based occupational exposure assessment approach has been considered the reference method for retrospective population-based studies, its implementation in large study samples has become prohibitive. To facilitate its application and improve upon it we developed, in the context of a Montreal population-based study of prostate cancer (PROtEuS), a hybrid approach combining job-exposure profiles (JEPs) summarizing expert evaluations from previous studies and expert review. We aim to describe the hybrid expert method and its impacts on the exposures assigned in PROtEuS compared to those from a previous study coded using the traditional expert method. METHODS: Applying the hybrid approach, experts evaluated semi-quantitative levels of confidence, concentration and frequency of exposure to 313 agents for 16,065 jobs held by 4005 subjects in PROtEuS. These assessments were compared to those from a different set of jobs coded in an earlier study of lung cancer, conducted on the same study base, for 90 blue-collar occupations and 203 agents. Endpoints evaluated included differences in the number of exposures and in the distribution of ratings across jobs, and the within-occupation variability in exposure. RESULTS: Compared to jobs from the lung cancer study, jobs in PROtEuS had on average 0.3 more exposures. PROtEuS exposures were more often assigned definite confidence ratings, but concentration and frequency levels tended to be lower. The within-occupation variability in ratings assigned to jobs were lower in PROtEuS jobs for all metrics. This was particularly evident for concentration, although considerable variability remained with over 40% of occupation/agent cells in PROtEuS exposed at different levels. The hybrid approach reduced coding time by half, compared to the traditional expert assessment. CONCLUSIONS: The new hybrid expert approach improved on efficiency and transparency, and resulted in greater confidence in assessments, compared to the traditional expert method applied in an earlier study involving a similar set of jobs. Assigned ratings were more homogeneous with the hybrid approach, possibly reflecting clearer guidelines for coding, greater coherence between experts and/or reliance on summaries of past assessments. Nevertheless, significant within-occupation variability remained with the hybrid approach, suggesting that experts took into account job-specific factors in their assessments.

Shared social mechanisms underlying the risk of nine cancers: A life course study.

Identifying life periods during which social conditions have the highest impact on risk of common cancers in a population may help to reveal their underlying shared social mechanisms. We used the life course framework to estimate the extent to which life course SEP is associated with risk of nine cancers. In addition, we tested whether these associations conform to a critical period or cumulative life course model. Data were from a population-based case-control study of occupational exposures and cancer conducted in Montreal, Canada. Participants were males aged 35-70 years (n = 2,547) residing in the Montreal metropolitan area with primary, histologically confirmed cancers diagnosed between 1979 and 1985. Population controls (n = 512) were sampled from electoral lists. SEP was measured at three different periods of life based on respondent's report: during childhood, young adulthood and mid-life. We used a structured modeling approach using a series of unconditional logistic regressions to test which models best fit the data. Life course SEP increased the risk of all cancers. SEP in childhood was identified as a critical period for prostate and all gastrointestinal tract cancers except for esophagus cancer. In addition, the accumulation model best explained the data for melanoma and lung squamous cell carcinoma. Our findings suggest that childhood social circumstances are a common risk factor for several cancers among men; our results provide insights into the mechanisms involved in the etiology of nine cancers.

Inter-rater Agreement Between Exposure Assessment Using Automatic Algorithms and Using Experts.

Objectives: To estimate the inter-rater agreement between exposure assessment to asthmagens in current jobs by algorithms based on task-based questionnaires (OccIDEAS) and by experts. Methods: Participants in a cross-sectional national survey of exposure to asthmagens (AWES-Asthma) were randomly split into two subcohorts of equal size. Subcohort 1 was used to determine the most common asthmagen groups and occupational groups. From subcohort 2, a random sample of 200 participants was drawn and current occupational exposure (yes/no) was assessed in these by OccIDEAS and by two experts independently and then as a consensus. Inter-rater agreement was estimated using Cohen's Kappa coefficient. The null hypothesis was set at 0.4, because both the experts and the automatic algorithm assessed the exposure using the same task-based questionnaires and therefore an agreement better than by chance would be expected. Results: The Kappa coefficients for the agreement between the experts and the algorithm-based assessments ranged from 0.37 to 1, while the agreement between the two experts ranged from 0.29 to 0.94, depending on the agent being assessed. After discussion by both experts the Kappa coefficients for the consensus decision and OccIDEAS were significantly larger than 0.4 for 7 of the 10 asthmagen groups, while overall the inter-rater agreement was greater than by chance (P < 0.0001). Conclusions: The web-based application OccIDEAS is an appropriate tool for automated assessment of current exposure to asthmagens (yes/no), and requires less time-consuming work by highly-qualified research personnel than the traditional expert-based method. Further, it can learn and reuse expert determinations in future studies.

Occupational exposure to high-frequency electromagnetic fields and brain tumor risk in the INTEROCC study: An individualized assessment approach.

INTRODUCTION: In 2011, the International Agency for Research on Cancer classified radiofrequency (RF) electromagnetic fields (EMF) as possibly carcinogenic to humans (group 2B), although the epidemiological evidence for the association between occupational exposure to RF-EMF and cancer was judged to be inadequate, due in part to limitations in exposure assessment. This study examines the relation between occupational RF and intermediate frequency (IF) EMF exposure and brain tumor (glioma and meningioma) risk in the INTEROCC multinational population-based case-control study (with nearly 4000 cases and over 5000 controls), using a novel exposure assessment approach. METHODS: Individual indices of cumulative exposure to RF and IF-EMF (overall and in specific exposure time windows) were assigned to study participants using a source-exposure matrix and detailed interview data on work with or nearby EMF sources. Conditional logistic regression was used to investigate associations with glioma and meningioma risk. RESULTS: Overall, around 10% of study participants were exposed to RF while only 1% were exposed to IF-EMF. There was no clear evidence for a positive association between RF or IF-EMF and the brain tumors studied, with most results showing either no association or odds ratios (ORs) below 1.0. The largest adjusted ORs were obtained for cumulative exposure to RF magnetic fields (as A/m-years) in the highest exposed category (≥90th percentile) for the most recent exposure time window (1-4 years before the diagnosis or reference date) for both glioma, OR = 1.62 (95% confidence interval (CI): 0.86, 3.01) and meningioma (OR = 1.52, 95% CI: 0.65, 3.55). CONCLUSION: Despite the improved exposure assessment approach used in this study, no clear associations were identified. However, the results obtained for recent exposure to RF electric and magnetic fields are suggestive of a potential role in brain tumor promotion/progression and should be further investigated.

Evaluating the Validity of a Two-stage Sample in a Birth Cohort Established from Administrative Databases.

BACKGROUND: When using administrative databases for epidemiologic research, a subsample of subjects can be interviewed, eliciting information on undocumented confounders. This article presents a thorough investigation of the validity of a two-stage sample encompassing an assessment of nonparticipation and quantification of the extent of bias. METHODS: Established through record linkage of administrative databases, the Québec Birth Cohort on Immunity and Health (n = 81,496) aims to study the association between Bacillus Calmette-Guérin vaccination and asthma. Among 76,623 subjects classified in four Bacillus Calmette-Guérin-asthma strata, a two-stage sampling strategy with a balanced design was used to randomly select individuals for interviews. We compared stratum-specific sociodemographic characteristics and healthcare utilization of stage 2 participants (n = 1,643) with those of eligible nonparticipants (n = 74,980) and nonrespondents (n = 3,157). We used logistic regression to determine whether participation varied across strata according to these characteristics. The effect of nonparticipation was described by the relative odds ratio (ROR = ORparticipants/ORsource population) for the association between sociodemographic characteristics and asthma. RESULTS: Parental age at childbirth, area of residence, family income, and healthcare utilization were comparable between groups. Participants were slightly more likely to be women and have a mother born in Québec. Participation did not vary across strata by sex, parental birthplace, or material and social deprivation. Estimates were not biased by nonparticipation; most RORs were below one and bias never exceeded 20%. CONCLUSIONS: Our analyses evaluate and provide a detailed demonstration of the validity of a two-stage sample for researchers assembling similar research infrastructures.

Socioeconomic position and lung cancer risk: how important is the modeling of smoking?

BACKGROUND: Although it has been reported that low socioeconomic position (SEP) is associated with lung cancer, the extent to which this reflects SEP differences in cigarette smoking is unclear. We investigated how various modeling approaches for smoking might influence this observed association. METHODS: We used data from a case-control study conducted in Montreal, Canada (1996-2002), comprising 1203 subjects with incident lung cancer and 1513 population controls. SEP was measured by census-based and self-reported income, residential value, education level, and occupational class. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated using logistic regression, and Akaike's Information Criterion (AIC) was used to compare model fit. RESULTS: Associations were observed between SEP indicators and lung cancer, but gradually disappeared with more comprehensive adjustment for smoking. For comparisons of the highest to lowest categories of census-based income, the OR for lung cancer was 0.58 (95% CI = 0.32-1.05) when adjusting only for smoking status (never, former, current), but 0.97 (0.51-1.86) when adjusting for smoking status, cigarette-years, and time since cessation. For comparisons of highest to lowest levels of education, the ORs for lung cancer were 0.50 (0.38-0.65) and 0.76 (0.57-1.02), when making the least and most comprehensive adjustments for smoking, respectively. Similarly, comparing highly skilled with unskilled manual workers, the ORs were 0.78 (0.54-1.12) and 1.00 (0.68-1.47), respectively. With thorough smoking adjustment, associations between SEP indicators and lung cancer virtually disappeared, and SEP did not improve model fit. CONCLUSIONS: Previously reported associations of SEP with lung cancer may be attributable to incomplete adjustment for smoking. Our findings underline the importance of adjusting for several dimensions of smoking behavior to make correct inferences.

Comparison of indicators of material circumstances in the context of an epidemiological study.

BACKGROUND: Since individual-level income is difficult to collect, investigators often rely on group-based measures derived from census data. No study has assessed the use of residential property values as an indicator of individual material circumstances. We aimed to compare two proxy indicators of material circumstances, one based on residential value and the other on median census tract income, to self-reported household income. METHODS: We used data from a case-control study (1996-2002), restricting analyses to 676 residents of the Island of Montreal for whom the three indicators were available. The degree of discrepancy between the residential value index, census income, and self-reported household income--each in 5 categories--was estimated, along with overall and weighted Kappas. RESULTS: When comparing residential value index and census income to self-reported household income, perfect concordance was observed for 38% and 30% of subjects, respectively; very good concordance, defined as ≤1 category difference, was observed for 76% and 69% of subjects, respectively. When compared to self-reported household income, overall and weighted Kappas showed stronger agreement with residential value index (weighted Kappa=0.37, 95% CI: 0.32, 0.42) than with census income (weighted Kappa=0.25, 95% CI: 0.20, 0.30). CONCLUSIONS: A residential value index may provide a measure of material circumstances that is closer to self-reported household income than the commonly used census income. Each indicator presents advantages and disadvantages, and their choice may depend on study objectives and feasibility.

Recall bias in the assessment of exposure to mobile phones.

Most studies of mobile phone use are case-control studies that rely on participants' reports of past phone use for their exposure assessment. Differential errors in recalled phone use are a major concern in such studies. INTERPHONE, a multinational case-control study of brain tumour risk and mobile phone use, included validation studies to quantify such errors and evaluate the potential for recall bias. Mobile phone records of 212 cases and 296 controls were collected from network operators in three INTERPHONE countries over an average of 2 years, and compared with mobile phone use reported at interview. The ratio of reported to recorded phone use was analysed as measure of agreement. Mean ratios were virtually the same for cases and controls: both underestimated number of calls by a factor of 0.81 and overestimated call duration by a factor of 1.4. For cases, but not controls, ratios increased with increasing time before the interview; however, these trends were based on few subjects with long-term data. Ratios increased by level of use. Random recall errors were large. In conclusion, there was little evidence for differential recall errors overall or in recent time periods. However, apparent overestimation by cases in more distant time periods could cause positive bias in estimates of disease risk associated with mobile phone use.

Validation of expert assessment of occupational exposures.

BACKGROUND: Assessment by experts may be the best method available for retrospective occupational exposure measurement in community-based studies. This study was undertaken to examine the validity of occupational exposure assessment by comparing the ratings of experienced raters with previously recorded industrial hygiene measurements. METHODS: We obtained 50 measurements from industrial hygiene records, covering a variety of jobs and substances and created 47 job descriptions around these measurements. Three raters were asked to assess exposure to a checklist of 19 substances (including those substances which had been measured). We estimated the sensitivity of the raters in correctly detecting those substances known to have been present. RESULTS: Using a liberal criterion for the ratings, the average sensitivity among the raters was 90%. Using a more stringent criterion, the average sensitivity was 73%. Among substances coded as present, the raters were quite accurate in rating the relative concentration and frequency of exposure. CONCLUSIONS: This trial demonstrated that a team of experienced raters could successfully characterize jobs in which important exposures occurred.