Work was performed at National Institute for Occupational Safety and Health.
Article first published online: 18 NOV 2002
Published 2002 Wiley-Liss, Inc.
American Journal of Industrial Medicine
Volume 42, Issue 6, pages 481–489, December 2002
How to Cite
Silver, S.R., Rinsky, R.A., Cooper, S.P., Hornung, R.W. and Lai, D. (2002), 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. Am. J. Ind. Med., 42: 481–489. doi: 10.1002/ajim.10139
Mention of company names or products does not constitute endorsement by the National Institute for Occupational Safety and Health.
This article is a US Government work and, as such, is in the public domain in the United States of America.
- Issue published online: 18 NOV 2002
- Article first published online: 18 NOV 2002
- Manuscript Accepted: 10 AUG 2002
- risk estimates;
- temporal changes;
- follow-up time;
- rubber workers;
- risk analysis
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.
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.
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.