Effect of follow-up time on risk estimates: A longitudinal examination of the relative risks of leukemia and multiple myeloma in a rubber hydrochloride cohort

Background Choice of follow‐up time for an occupational cohort can influence risk estimates. We examined the effects of follow‐up time on relative risk estimates for leukemia and multiple myeloma in a cohort of 1,845 rubber hydrochloride workers. Materials and Methods We generated standardized morta...

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Bibliographic Details
Published in:American journal of industrial medicine 2002-12, Vol.42 (6), p.481-489
Main Authors: Silver, S.R., Rinsky, R.A., Cooper, S.P., Hornung, R.W., Lai, D.
Format: Article
Language:English
Subjects:
benzene
Benzene - adverse effects
Biological and medical sciences
Cohort Studies
Dose-Response Relationship, Drug
follow-up time
Hematologic and hematopoietic diseases
Humans
leukemia
Leukemia - chemically induced
Leukemia - mortality
Leukemias. Malignant lymphomas. Malignant reticulosis. Myelofibrosis
Longitudinal Studies
Male
Medical sciences
Multiple Myeloma - chemically induced
Multiple Myeloma - mortality
Occupational Diseases - chemically induced
Occupational Diseases - mortality
Occupational Exposure
Proportional Hazards Models
risk analysis
Risk Assessment
risk estimates
Rubber
rubber workers
temporal changes
Time Factors
United States - epidemiology
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Summary:Background Choice of follow‐up time for an occupational cohort can influence risk estimates. We examined the effects of follow‐up time on relative risk estimates for leukemia and multiple myeloma in a cohort of 1,845 rubber hydrochloride workers. Materials and Methods We generated standardized mortality ratios (SMRs) for yearly follow‐ups, beginning each study in 1940 and increasing study end dates from 1950 through 1996. We used Cox proportional hazards modeling to explore the effects of follow‐up time on the exposure–response relationship. Results The SMR for leukemia rose to 13.55 in 1961 and fell nearly monotonically to 2.47 by 1996. Cox modeling suggested interaction between cumulative exposure and time since exposure. A longer time to peak risk was seen for multiple myeloma. Conclusions Because summary risk estimates change with follow‐up time, exposure limits set using these estimates may not adequately protect workers. Consideration of appropriate follow‐up time and use of more complex temporal models are critical to the risk assessment process. Am. J. Ind. Med. 42:481–489, 2002. Published 2002 Wiley‐Liss, Inc.
ISSN:0271-3586
1097-0274
DOI:10.1002/ajim.10139