EVALUATING ALTERNATIVE EXPOSURE INDEXES IN EPIDEMIOLOGIC STUDIES ON EXTREMELY-LOW-FREQUENCY MAGNETIC-FIELDS

Citation
J. Juutilainen et al., EVALUATING ALTERNATIVE EXPOSURE INDEXES IN EPIDEMIOLOGIC STUDIES ON EXTREMELY-LOW-FREQUENCY MAGNETIC-FIELDS, Bioelectromagnetics, 17(2), 1996, pp. 138-143
Citations number
14
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biophysics
Journal title
ISSN journal
0197-8462
Volume
17
Issue
2
Year of publication
1996
Pages
138 - 143
Database
ISI
SICI code
0197-8462(1996)17:2<138:EAEIIE>2.0.ZU;2-N
Abstract
Choosing the right exposure index for epidemiological studies on 50-60 Hz magnetic fields is difficult due to the lack of knowledge about cr itical exposure parameters for the biological effects of magnetic fiel ds. This paper uses data from a previously published epidemiological i nvestigation on early pregnancy loss (EPL) to study the methods of eva luating the exposure-response relationship of 50 Hz magnetic fields. T wo approaches were used. The first approach was to apply generalized a dditive modeling to suggest the functional form of the relationship be tween EPL and magnetic field strength. The second approach evaluated t he goodness of fit of the EPL data with eight alternative exposure ind ices: the 24 h average of magnetic field strength, three indices measu ring the proportion of time above specified thresholds, and four indic es measuring the proportion of time within specified intensity windows . Because the original exposure data included only spot measurements, estimates for the selected exposure indices were calculated indirectly from the spot measurements using empirical nonlinear equations derive d from 24 h recordings in 60 residences. The results did not support i ntensity windows, and a threshold-type dependence on field strength ap peared to be more plausible than a linear relationship. In addition, t he study produced data suggesting that spot measurements may be used a s surrogates for other exposure indices besides the time average field strength. No final conclusions should be drawn from this study alone, but we hope that this exercise stimulates evaluation of alternative e xposure indices in other planned and ongoing epidemiological studies. (C) 1996 Wiley-Liss, Inc.