Which Environmental Factor Is Correlated with Long-Term Multiple Sclerosis Incidence Trends: Ultraviolet B Radiation or Geomagnetic Disturbances?

Seyed Aidin Sajedi,Fahimeh Abdollahi

doi:10.1155/2017/4960386

Seyed Aidin Sajedi, Fahimeh Abdollahi

Open Access

https://doi.org/10.1155/2017/4960386

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Abstract

Background Insufficient received ultraviolet B radiation (UV) is regarded as the main environmental risk factor (RF) for MS in vitamin D deficiency hypothesis. Nevertheless, geomagnetic disturbance (GMD) has also been proposed as a potential trigger for MS in GMD hypothesis. The aim of this study was to investigate which of these mentioned RF is correlated with long-term ultradecadal MS incidence. Methods After a systematic search, long-term incidence reports of the United Kingdom (UK), Denmark, Tayside County, Nordland County, the Orkney, and Shetland Islands were selected for this retrospective time-series study. Possible lead-lag relationships between MS incidence, GMD, and UV were evaluated by cross-correlation analysis. Results Significant positive correlations between GMD and MS incidence were seen in Tayside County (at lag of 2 years: rS = 0.38), Denmark (peak correlation at lag of 2 years: rS = 0.53), and UK (at lag of 1 year: rS = 0.50). We found a positive correlation between received UV and MS incidences in the Nordland at lag of 1 year (rS = 0.49). Conclusion This study found significant positive correlations between alterations in GMD with alterations in long-term MS incidence in three out of six studied locations and supports the GMD hypothesis. The observed significant correlation between MS and UV is positive; hence it is not supportive for UV related vitamin D deficiency hypothesis.

Highlights

Multiple sclerosis (MS) is the most common disabling neurological disorder in the young adults
While we know that the climate and temperature are not the risk factors for MS, it seems logical that biomedical researchers suppose that the only remained environmental factor that significantly changes with the latitude and seasons, with the ability to cause a known biological effect, is the received solar ultraviolet radiation (UV)
In spite of primary suggestions by some researchers in the past decades [8, 9], we found that this issue as a possible environmental risk factor for MS has been neglected, and no comprehensive hypothesis has been designed to explain the potential relationship between geomagnetic disturbance (GMD) and MS

Summary

Introduction

Multiple sclerosis (MS) is the most common disabling neurological disorder in the young adults. Genetic studies of twins have revealed that the role of genes in MS is utmost 30% as a factor of susceptibility, and considering the special epidemiological features of MS, the remained roles are played by one or multiple nongenetic, environmental triggers. The majority of MS researchers have focused on vitamin D deficiency as a potential risk factor for this disease. Insufficient received ultraviolet B radiation (UV) is regarded as the main environmental risk factor (RF) for MS in vitamin D deficiency hypothesis. This study found significant positive correlations between alterations in GMD with alterations in long-term MS incidence in three out of six studied locations and supports the GMD hypothesis. The observed significant correlation between MS and UV is positive; it is not supportive for UV related vitamin D deficiency hypothesis

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