Left Truncation, Susceptibility, and Bias in Occupational Cohort Studies

Details

• Alternative Title:
  Epidemiology
• Personal Author:
  Applebaum, Katie M. ; Malloy, Elizabeth J. ; Eisen, Ellen A.
• Description:
  Background
  
  Left truncation occurs when subjects who otherwise meet entry criteria do not remain observable for a later start of follow-up. We investigated left truncation in occupational studies due to inclusion of workers hired before the start of follow-up in a simulation study.
  
  Methods
  
  Using Monte Carlo methods, we simulated null and positive associations between exposure (work duration) and mortality for 500 datasets of 5000 subjects, assuming the absence and presence of heterogeneity in susceptibility to disease and to the effect of exposure. We examined incident hires (followed since hire) and left-truncated prevalent hires (those hired before baseline and remained employed at baseline). We estimated the association ( β^1∗) as the mean slope using Cox proportional hazards with a linear term for exposure, under scenarios with and without susceptibility.
  
  Results
  
  With homogeneous susceptibility, there were no differences between incident and prevalent hires. Introducing only disease susceptibility did not change results. However, with heterogeneous susceptibility to the effect of exposure, downward bias was observed among prevalent hires under both the true null and positive exposure-response scenarios. The bias increased with time between hire and baseline (null: β^1∗=0.05[SD=0.08],β^1∗=-0.08[SD=0.24],β^1∗=-0.18[SD=0.98] if hired <15, 15 to <30, and ≥30 years before baseline, respectively), coincident with a decreasing percentage of susceptible subjects.
  
  
• Subjects:
  Bias Cohort Studies Epidemiologic Research Design Follow-Up Studies Humans Monte Carlo Method Occupational Diseases Occupational Exposure Proportional Hazards Models
• Source:
  Epidemiology. 2011; 22(4):599-606
• Pubmed ID:
  21543985
• Pubmed Central ID:
  PMC4153398
• Document Type:
  Journal Article
• Funding:
  K01 OH009390/OH/NIOSH CDC HHSUnited States/ ; R01 CA081345/CA/NCI NIH HHSUnited States/ ; K01OH009390/OH/NIOSH CDC HHSUnited States/
• Volume:
  22
• Issue:
  4
• Collection(s):
  CDC Public Access
• Main Document Checksum:
  urn:sha256:8b4a7aa8afe91c0f1f40b89581429b10bf2aae258645fdfb60d8b3a1f13cf521
• Download URL:
  https://stacks.cdc.gov/view/cdc/33715/cdc_33715_DS1.pdf
• File Type:
  [PDF - 329.96 KB ]