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.

AI evidence extraction

Main findings

In 3,555,064 adults (55.4 million person-years; 146,655 NDD deaths), long-term ELF-MF exposure from high-voltage power lines (50 Hz) was positively associated with dementia mortality (AD: HR per 1 µT increase 1.54, 95% CI 1.23–1.92; OTD: HR 1.31, 95% CI 1.13–1.52). Associations for railway-line exposure (16.7 Hz) were weaker and attenuated after adjustment for environmental co-exposures. No associations were observed for ALS, PD, or MS.

Outcomes measured

• Mortality from Alzheimer's disease (AD)
• Mortality from other types of dementia (OTD)
• Mortality from amyotrophic lateral sclerosis (ALS)
• Mortality from Parkinson's disease (PD)
• Mortality from multiple sclerosis (MS)
• Neurodegenerative disease (NDD) mortality (overall)

Limitations

• Epidemiological evidence described as inconsistent in background
• Railway-line associations attenuated after adjusting for environmental co-exposures (potential confounding)
• Causal inference limited by absence of established biological mechanisms
• Exposure based on modelled proximity models (not direct personal measurements)

Suggested hubs

• occupational-exposure (0.05)
  Study is residential/general population rather than occupational; included only weakly as it concerns long-term ELF exposure sources.

{
    "study_type": "cohort",
    "exposure": {
        "band": "ELF",
        "source": "high-voltage power lines; railway lines",
        "frequency_mhz": null,
        "sar_wkg": null,
        "duration": "Long-term exposure calculated as time-weighted average over 10-year windows preceding each interval (2001-2005, 2006-2010, 2011-2015, 2016-2018)"
    },
    "population": "Adults in the Swiss National Cohort (Switzerland), followed 2001–2018",
    "sample_size": 3555064,
    "outcomes": [
        "Mortality from Alzheimer's disease (AD)",
        "Mortality from other types of dementia (OTD)",
        "Mortality from amyotrophic lateral sclerosis (ALS)",
        "Mortality from Parkinson's disease (PD)",
        "Mortality from multiple sclerosis (MS)",
        "Neurodegenerative disease (NDD) mortality (overall)"
    ],
    "main_findings": "In 3,555,064 adults (55.4 million person-years; 146,655 NDD deaths), long-term ELF-MF exposure from high-voltage power lines (50 Hz) was positively associated with dementia mortality (AD: HR per 1 µT increase 1.54, 95% CI 1.23–1.92; OTD: HR 1.31, 95% CI 1.13–1.52). Associations for railway-line exposure (16.7 Hz) were weaker and attenuated after adjustment for environmental co-exposures. No associations were observed for ALS, PD, or MS.",
    "effect_direction": "mixed",
    "limitations": [
        "Epidemiological evidence described as inconsistent in background",
        "Railway-line associations attenuated after adjusting for environmental co-exposures (potential confounding)",
        "Causal inference limited by absence of established biological mechanisms",
        "Exposure based on modelled proximity models (not direct personal measurements)"
    ],
    "evidence_strength": "moderate",
    "confidence": 0.7800000000000000266453525910037569701671600341796875,
    "peer_reviewed_likely": "yes",
    "keywords": [
        "extremely low-frequency magnetic fields",
        "ELF-MF",
        "high-voltage power lines",
        "railway lines",
        "residential exposure",
        "proximity model",
        "cohort study",
        "Swiss National Cohort",
        "neurodegenerative disease mortality",
        "Alzheimer's disease",
        "dementia",
        "amyotrophic lateral sclerosis",
        "Parkinson's disease",
        "multiple sclerosis"
    ],
    "suggested_hubs": [
        {
            "slug": "occupational-exposure",
            "weight": 0.05000000000000000277555756156289135105907917022705078125,
            "reason": "Study is residential/general population rather than occupational; included only weakly as it concerns long-term ELF exposure sources."
        }
    ]
}

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