Smoothing in Occupational Cohort Studies: An Illustration Based on Penalised Splines

Details

• Personal Author:
  Agalliu I ; Checkoway, Harvey ; Coull BA ; Eisen EA ; Thurston SW
• Description:
  AIMS: To illustrate the contribution of smoothing methods to modelling exposure-response data, Cox models with penalised splines were used to reanalyse lung cancer risk in a cohort of workers exposed to silica in California's diatomaceous earth industry. To encourage application of this approach, computer code is provided. METHODS: Relying on graphic plots of hazard ratios as smooth functions of exposure, the sensitivity of the curve to amount of smoothing, length of the exposure lag, and the influence of the highest exposures was evaluated. Trimming and data transformations were used to down-weight influential observations. RESULTS: The estimated hazard ratio increased steeply with cumulative silica exposure before flattening and then declining over the sparser regions of exposure. The curve was sensitive to changes in degrees of freedom, but insensitive to the number or location of knots. As the length of lag increased, so did the maximum hazard ratio, but the shape was similar. Deleting the two highest exposed subjects eliminated the top half of the range and allowed the hazard ratio to continue to rise. The shape of the splines suggested a parametric model with log hazard as a linear function of log transformed exposure would fit well. CONCLUSIONS: This flexible statistical approach reduces the dependence on a priori assumptions, while pointing to a suitable parametric model if one exists. In the absence of an appropriate parametric form, however, splines can provide exposure-response information useful for aetiological research and public health intervention. [Description provided by NIOSH]
• Subjects:
  Coal Coal Mining Mining Occupational Health Safety
• Keywords:
  Cancer Diatomaceous Earth Exposure Levels Hazards Lung Lung Cancer Models Risk Factors Silica Work Environment Workers

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• ISSN:
  1351-0711
• Document Type:
  Text
• Funding:
  Grant
• Genre:
  Journal Article
• Place as Subject:
  Massachusetts ; OSHA Region 1
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  61
• Issue:
  10
• NIOSHTIC Number:
  nn:20055511
• Citation:
  Occup Environ Med 2004 Oct; 61(10):854-860
• Contact Point Address:
  Prof. E A Eisen, Occupational Health Program, Harvard School of Public Health, 665 Huntington Avenue, Boston, MA 02115
• Email:
  eeisen@hsph.harvard.edu
• CAS Registry Number:
  Silica (CAS RN 7631-86-9)
• Federal Fiscal Year:
  2005
• Performing Organization:
  Harvard School of Public Health
• Peer Reviewed:
  True
• Start Date:
  20030701
• Source Full Name:
  Occupational and Environmental Medicine
• End Date:
  20050630
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:9bcf1a825ee4abd9f6f34a526be914f2fdaf60147c7dc19ae3775e57df39b1fd5017b2d1f7df8cf9ad6bd3dbdcaf85c26bdb4b865b78bfa1d8cb50703261d3cf
• Download URL:
  https://stacks.cdc.gov/view/cdc/213348/cdc_213348_DS1.pdf
• File Type:
  [PDF - 169.62 KB ]