For years, scientists and researchers have theorized that sunlight can influence multiple sclerosis prevalence. The latitude hypothesis is the idea that the distance from the equator (latitude) can be related to multiple sclerosis prevalence. This hypothesis dives deeper into the complex relationship that MS has with vitamin D levels, and may even provide valuable insight into vitamin D-using treatments for MS. However, not everyone has agreed with this hypothesis.
Latitude, as per the latitude hypothesis, is a risk factor in multiple sclerosis, meaning that the amount of sun exposure can impact a person’s protection from the autoimmune disease. This hypothesis has been tested by various studies, from those focusing on environmental effects on MS to those focused on finding variables in the hypothesis, and it has been established that there is some link to vitamin D levels and MS. The most widely agreed upon understanding of the relationship is that low levels of sunlight and vitamin D could be leading to an impairment of the immune system, something that leaves it more vulnerable to MS. Professionals have looked into the viability of recommending vitamin D3 supplements to patients with relapsing-remitting MS, in order to further aid their treatment.
Alternatively, many researchers disagree with elements of the hypothesis, claiming that while latitude may influence MS prevalence, the real issue may be the health expenditure of the sample areas. When tested, researchers found that countries with lower health expenditures per capita had less MS prevalence, with 10 out 100,000 people diagnosed with MS versus the 46 out of 100,000 in countries with a higher health expenditure per capita (Kneisel). With this, researchers have found that due to less health expenditure, fewer people have the resources available to them to be diagnosed with MS, given the rare nature of the condition.
Overall, the latitude hypothesis has been partially supported by many over the years, but emerging research and new discoveries have raised questions about some elements of the theory. Researchers continue to explore the interesting relationships between latitude, vitamin D levels, and multiple sclerosis, finding new treatments that can hopefully aid in the fight against MS.
Works Cited:
Kneisel, Kate. “What's Behind the Stark Regional Variations in MS Prevalence?” Medpage Today, 25 August 2022, https://www.medpagetoday.com/neurology/multiplesclerosis/100396. Accessed 29 August 2022.
Rosen, L.N., et al. “Multiple Sclerosis and latitude: A new perspective on an old association.” Medical Hypotheses, vol. 36, no. 4, 1991, pp. 376-378. Science Direct, https://www.sciencedirect.com/science/article/abs/pii/030698779190014P. Accessed 29 August 2022.
Simpson, Steve Jr et al. “Latitude continues to be significantly associated with the prevalence of
multiple sclerosis: an updated meta-analysis.” Journal of neurology, neurosurgery, and
psychiatry vol. 90,11 (2019): 1193-1200. doi:10.1136/jnnp-2018-320189
Wood, H. Latitude and vitamin D influence disease course in multiple sclerosis. Nat Rev Neurol
13, 3 (2017). https://doi.org/10.1038/nrneurol.2016.181
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