Quantile Regression for Longitudinal Data with Values Below the Limit of Detection and Time-Dependent Covariates – Application to Modeling Carbon Nanotube and Nanofiber Exposures

Details

• Personal Author:
  Bertke S ; Chen I-C ; Dahm, Matthew M.
• Description:
  Background: In studies of occupational health, longitudinal environmental exposure, and biomonitoring data are often subject to right skewing and left censoring, in which measurements fall below the limit of detection (LOD). To address right-skewed data, it is common practice to log-transform the data and model the geometric mean, assuming a log-normal distribution. However, if the transformed data do not follow a known distribution, modeling the mean of exposure may result in bias and reduce efficiency. In addition, when examining longitudinal data, it is possible that certain covariates may vary over time. Objective: To develop predictive quantile regression models to resolve the issues of left censoring and time-dependent covariates and to quantitatively evaluate if previous and current covariates can predict current and/or future exposure levels. Methods: To address these gaps, we suggested incorporating different substitution approaches into quantile regression and utilizing a method for selecting a working type of time dependency for covariates. Results: In a simulation study, we demonstrated that, under different types of time-dependent covariates, the approach of multiple random value imputation outperformed the other approaches. We also applied our methods to a carbon nanotube and nanofiber exposure study. The dependent variables are the left-censored mass of elemental carbon at both the respirable and inhalable aerosol size fractions. In this study, we identified some potential time-dependent covariates with respect to worker-level determinants and job tasks. Conclusion: Time dependency for covariates is rarely accounted for when analyzing longitudinal environmental exposure and biomonitoring data with values less than the LOD through predictive modeling. Mistreating the time-dependency as time-independency will lead to an efficiency loss of regression parameter estimation. Therefore, we addressed time-varying covariates in longitudinal exposure and biomonitoring data with left-censored measurements and illustrated an entire conditional distribution through different quantiles. [Description provided by NIOSH]
• Subjects:
  Environmental Exposure Occupational Health Safety
• Keywords:
  Analytical Models Author Keywords: Biomonitoring Biomonitoring Environmental Exposure Left Censoring Limit Of Detection LOD Quantile Regression Statistical Analysis Statistical Quality Control Time-dependent Covariate

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• ISSN:
  2398-7308
• Document Type:
  Text
• Genre:
  Journal Article
• Place as Subject:
  Chicago Region [OSHA] ; Ohio
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DFSE - Division of Field Studies and Engineering
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  68
• Issue:
  8
• NIOSHTIC Number:
  nn:20070023
• Citation:
  Ann Work Expo Health 2024 Oct; 68(8):846-858
• Contact Point Address:
  I-Chen Chen, Division of Field Studies and Engineering, National Institute for Occupational Safety and Health, Centers for Disease Control and Prevention, 1090 Tusculum Avenue, MS-R14, Cincinnati, OH 45226, USA
• Email:
  okv0@cdc.gov
• Federal Fiscal Year:
  2025
• Peer Reviewed:
  True
• Source Full Name:
  Annals of Work Exposures and Health
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:25f660993705b8674f5a5e0870dfb5834dee39db009b0ca03a83e93a566e21685c3a937bca4c74979eb32139ff6f2794040d3415ce024bbb790632f3fe382637
• Download URL:
  https://stacks.cdc.gov/view/cdc/208329/cdc_208329_DS1.pdf
• File Type:
  [PDF - 3.57 MB ]