Long-term residential magnetic field exposure and neurodegenerative disease mortality: An 18-year nationwide cohort study in Switzerland

Abstract

BACKGROUND: Epidemiological evidence on the association between extremely low-frequency magnetic fields (ELF-MF) exposure and neurodegenerative diseases (NDD) remains inconsistent. Few population-based studies using exposure from high-voltage power lines (HVPL) have found mixed findings, and none have yet considered exposure from railway lines. METHODS: We followed 3,555,064 adults from the Swiss National Cohort (2001-2018), contributing 55.4 million person-years. Long-term ELF-MF exposure from HVPL (50 Hz) and railway lines (16.7 Hz) was modelled using validated proximity models and updated over four intervals (2001-2005, 2006-2010, 2011-2015, 2016-2018). Long-term ELF-MF exposure was calculated as a time-weighted average exposure over 10-year windows preceding each interval. Cox proportional hazards models estimated hazard ratios (HRs) for mortality from Alzheimer's disease (AD), other types of dementia (OTD), amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and multiple sclerosis (MS), adjusting for sociodemographic and environmental co-exposures. RESULTS: During follow-up, 146,655 NDD deaths occurred. Less than 1% of the population was exposed to long-term ELF-MF ≥ 0.3 µT from HVPL and 2.4% from railway lines. HVPL exposure was positively associated with mortality from AD (HR per 1 µT increase in exposure = 1.54; 95% CI: 1.23-1.92) and OTD (HR = 1.31; 95% CI: 1.13-1.52). Associations for railway exposure were weaker and attenuated after adjusting for environmental co-exposures. No associations were observed for ALS, PD, or MS. CONCLUSIONS: Long-term ELF-MF exposure was associated with higher dementia mortality risk in the general population, but not with ALS, PD, or MS. Causal inference remains limited by the absence of established biological mechanisms.