Statistical Modeling of Dose-Response Relationships.
NIOSH 1985 May:22 pages
The importance of taking time factors into consideration in quantitative risk assessments was discussed. According to the author, the time factor may be measured from the first or the last exposure to a carcinogen, as the chronological age of the exposed individual, or from a certain calendar year. In the multistage model of carcinogenesis, it is hypothesized that the transition of a normal cell to a malignant one takes place in several stages. A carcinogen is assumed to change the rate of transition from one stage to the next so that a single exposure will shorten the time it takes for a neoplasm to appear. The standardized mortality ratio was discussed in mathematical terms and the importance of time factors was stressed. Several statistical pitfalls in the model were discussed: the question of whether the relative risk is constant or evolves with time, the allocation of person years to time periods, the allocation of person years to prevalent cohorts, noncontinuous follow up, continuous and discrete time, and latency and the average time to disease. In addition, the separate effects of multiple time scales were considered and treated mathematically. The author concludes that the risk is not a function of a single time scale but a complex function of multiple time scales which routinely should be addressed in all epidemiological studies.
Carcinogenicity; Cancer-rates; Epidemiology; Risk-analysis; Mortality-rates; Biostatistics; Mathematical-models; Humans; Models;
Proceedings of a Symposium on Epidemiology and Health Risk Assessment, Columbia, Maryland, May 14-16, 1985, Centers for Disease Control/NIOSH, 22 pages, 14 references