Extremely-low-frequency magnetic field (ELF-MF) exposure is suspected to increase the risk of Alzheimer's disease. Such fields are present in the vicinity of electrical motors and other electric appliances containing coils.
We investigated lifetime occupational ELF-MF exposure in relation to Alzheimer's disease and dementia among a community dementia-free cohort (n = 931) age 75 years and older in Stockholm, Sweden. This cohort was followed from 1987–1989 until 1994–1996 to detect dementia cases (Diagnostic and Statistical Manual of Mental Disorders, revised 3rd edition criteria). Information on lifetime job history was obtained by interview, usually of next of kin. ELF-MF exposure was assessed using a job-exposure matrix, measurement on historical equipment, and expert estimation. We analyzed the data with Cox models controlling for potential confounders.
Dementia was diagnosed in 265 subjects, including 202 with Alzheimer's disease. Among men, ELF-MF exposure ≥0.2 μT in lifetime principal job was related to multivariate-adjusted relative risks of 2.3 (95% CI = 1.0–5.1) for Alzheimer's disease and 2.0 (1.1–3.7) for dementia. We found no association among women. A similar sex-specific pattern was seen for the associations with average ELF-MF exposure throughout the work life. A dose-response relation was suggested in men, with multivariate-adjusted relative risks of 2.4 (0.8–6.8) for Alzheimer's disease and 2.5 (1.1–5.6) for dementia for the upper tertile of lifetime average exposure.
Long-term occupational exposure to a higher ELF-MF level may increase the risk of Alzheimer's disease and dementia in men. Similar patterns were not seen in women, which may in part be the result of a greater exposure misclassification in women than in men.
From the *Aging Research Center, Division of Geriatric Epidemiology and Medicine, Department of Neurotec, Karolinska Institutet and the Stockholm Gerontology Research Center, Stockholm, Sweden; and the †Department of Occupational and Environmental Health, Stockholm County Council and the Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
Submitted 2 June 2003; final version accepted 6 July 2004.
This study was supported by grants from the Swedish Council for Social Research, the Swedish Council for Work Life Research, Swedish Research Council, the Gun och Bertil Stohnes Stiftelse, the Stiftelse för Gamla Tjänarinnor, and the Insamling Stiftelsen för Alzheimer och Demens Forskning (SADF) in Sweden.
Correspondence: Chengxuan Qiu, Stockholm Gerontology Research Center, Olivecronas väg 4 (Box 6401), S-113 82 Stockholm, Sweden. E-mail: firstname.lastname@example.org.