| Summary: | 碩士 === 國立成功大學 === 環境醫學研究所 === 102 === Background: Because of advances in science and technology, electronic equipment and products are being widely used to improve the quality of life. Consequently, electromagnetic field (EMF) is all over our environment, and the sources include household appliances, radio communication systems, and high voltage power lines, among others. Due to the wide range of sources, many people are concerned about exposure to EMF and its potential effects on health. Studies all over the world have found some people who suffer effect from EMF exposures and have non-specific symptoms. They are called to have “electromagnetic hypersensitivity” (EHS). According to World Health Organization (WHO), EHS is characterized by a variety of non-specific symptoms (redness and tingling on skin, fatigue, concentration difficulties, etc.) which afflicted individuals attribute to exposure to EMF. A study by Hallberg and Oberfeld predicted that the prevalence of EHS would increase all over the world. According to a Taiwan study in 2007, the prevalence of EHS (13.3%) was among the highest in the world. Studies have shown that the medical costs on these medically unexplained diseases (MUD) such as EHS, sick building syndrome and chronic fatigue syndrome were not properly used. Therefore, we need to pay attention to related issues of EHS and clarify the etiology and related factors, so that the waste in medical expenditure can be minimized. This study aimed to assess the changes in the prevalence of EHS in comparison with the 2007 study and to evaluate the factors related to the prevalence all over the world.
Methods: This is a cross-sectional study that adopts the same methods used in the 2007 study, which was a computer aided telephone interview that used random digit dialing telephone survey evaluating the prevalence of EHS in Taiwan. In addition, we systematically reviewed the published literature to identify factors related to EHS. We performed t -test, chi-square test, and logistic regression using SPSS 17.0 software to evaluate the differences in demographic variables between EHS and Non-EHS participants and used Mix 2.0 to perform meta-analyses of the literature.
Results: In the telephone survey, both the crude data and the weighted data showed no statistically significant differences in age, gender, education, and employment status between the EHS and Non-EHS groups. The only significant variables was restriction of daily activities, the odds ratios associated with EHS was 2.44 (95% confidence interval [CI]: 1.66-3.59) from crude data and 2.38 (1.60-3.53) from weighted data (P 〈 0.001).The prevalence weighted according to gender and age was 4.6% (3.9%-5.4%). The most commonly reported EMF source was mobile phone (23.5%), followed by base station (21.5%) and power line tower (9.4%). In the 2007 study, the prevalence of EHS was higher in men (14.0% vs. 12.6%) and in participants at the education level of high school, but in the current study the prevalence was higher in women (5.1% vs. 4.1%) and in participants with higher education (college and above). In order to estimate the risk difference between the two genders in different years, we used the test of homogeneity of the odds ratio and found no statistically significant differences (P = 0.15). Hence, we obtained common odds ratio of 1.05 (95%CI: 0.83-1.31). The two studies observed similar distributions of prevalence in the middle aged participants. In the 13 journal articles and 2 governmental reports included in the meta-analyses, the prevalence of EHS had an increasing trend by 2009, but decreased in Taiwan, Sweden, and Netherlands afterwards. In addition, female gender, middle-age, higher education, and single or widowed marital status were found to be risk factors.
Conclusions: The prevalence of EHS in Taiwan decreased since 2007, and this is consistent with the trends observed in Sweden and Netherlands. The risk factors for EHS include female gender, middle-age, higher education, and single or widowed marital status. However, high levels of heterogeneity were observed among studies, probably due to the differences in the general condition of the nations or research methods. Therefore, interpretation of the results of meta-analyses should be conservative.
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