DNC News

Does Season play a role in developing MS?

Jacob Schor, ND

April 15, 2006


Subject: Link between MS, season and vitamin D


One thought leads to another……

Thinking over the information I just wrote up on Diabetes (see last newsletter), I had to take just a few moments tolook something up......


The recent reports on the seasonal variation in diabetes onset and exacerbation have got me wondering. Diabetes isn't the only disease that can be linked to changing ultraviolet exposure and vitamin D deficiency. There are many, the best known is multiple sclerosis. The well known and bizarre conundrum of multiple sclerosis has always been one of place. The closer people live to the equator the less likely they are to get MS, the further away the more likely. In the very last few years this has been explained by varying levels of ultraviolet light exposure and resultant vitamin D levels. The higher one's vitamin D level the less likely one is to get the disease. Recent reports suggest that diabetes is most often diagnosed in March, when vitamin D levels are at their annual low point. Does the same sort of seasonal variation occur with multiple sclerosis?


The answer is ‘sort of.'


An Australian study from 2003 shows a protective effect of sun exposure during childhood and adolescence against MS. The amount of sun exposure during the winter months is the most important factor. [i] A Finnish study which looked at vitamin D levels in MS patients yields some intriguing findings. Comparing vitamin D levels in 40 MS patients and 40 controls showed no difference during the winter but significant differences during the summer months. MS patients had significantly lower than average vitamin D levels during the summer. [ii] This is interesting in light of a Spanish study published a few months prior that looked at what time of year MS was most likely to be diagnosed. Looking at the records of 32 patients it was determined that outbreaks of MS are more common in the summer than the winter. [iii] Of course we can argue that often with MS the symptoms appear months before the disease is diagnosed and depending on how squeaky the wheel is and how ponderously slow the healthcare system responds to individual patient complaints, there may be a lag time of several months between disease onset and diagnosis. And also of course, nothing against the Spanish, but it is pretty much sunny in Spain year round and how much seasonal variation do you expect to see? Of course the slight variations in vitamin D levels seen during varying seasons in Spain may be far outweighed by seasonal variations in temperature. It is well known that MS patients have poor heat tolerance and that simple hot weather may trigger exacerbations of the disease. [iv] Yet assume this article is accurate, that MS is triggered in the summer more often, when, according to the Finns, MS patient's have a lower than normal Vitamin D level. It sort of makes sense. That's what I mean by, ‘sort of.'


What isn't vague though is the effect that season of birth has in the long run on someone's chances of developing MS. A 2005 study in the British Medical Journal looked at 17,874 Canadian MS patients and 11,502 British MS patients, all living in less sunny climates than Spain . [v] The data showed a statistically significant advantage to being born in November. Those born in November had a lower than average chance of developing MS. The obvious explanation is that during their gestation period their mothers provided ample vitamin D for development.


This sort of information is behind an article in Medical Hypothesis titled, “Why we should offer routine vitamin D supplementation in pregnancy and childhood to prevent multiple sclerosis.” [vi] Of course prenatal supplementation may also lower risk of diabetes and a host of other diseases, but that's another story.






BMJ. 2003 Aug 9;327(7410):316.

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Past exposure to sun, skin phenotype, and risk of multiple sclerosis: case-control study.

van der Mei IA , Ponsonby AL , Dwyer T , Blizzard L , Simmons R , Taylor BV , Butzkueven H , Kilpatrick T .

Menzies Centre for Population Health Research,
University of Tasmania , Hobart , TAS 7000, Australia . Ingrid.vanderMei@utas.edu.au

OBJECTIVE: To examine whether past high sun exposure is associated with a reduced risk of multiple sclerosis. DESIGN: Population based case-control study. SETTING:
Tasmania , latitudes 41-3 degrees S. PARTICIPANTS: 136 cases with multiple sclerosis and 272 controls randomly drawn from the community and matched on sex and year of birth. MAIN OUTCOME MEASURE: Multiple sclerosis defined by both clinical and magnetic resonance imaging criteria. RESULTS: Higher sun exposure when aged 6-15 years (average 2-3 hours or more a day in summer during weekends and holidays) was associated with a decreased risk of multiple sclerosis (adjusted odds ratio 0.31, 95% confidence interval 0.16 to 0.59). Higher exposure in winter seemed more important than higher exposure in summer. Greater actinic damage was also independently associated with a decreased risk of multiple sclerosis (0.32, 0.11 to 0.88 for grades 4-6 disease). A dose-response relation was observed between multiple sclerosis and decreasing sun exposure when aged 6-15 years and with actinic damage. CONCLUSION: Higher sun exposure during childhood and early adolescence is associated with a reduced risk of multiple sclerosis. Insufficient ultraviolet radiation may therefore influence the development of multiple sclerosis.





Mult Scler. 2005 Jun;11(3):266-71.

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25-Hydroxyvitamin D levels in serum at the onset of multiple sclerosis.

Soilu-Hanninen M , Airas L , Mononen I , Heikkila A , Viljanen M , Hanninen A .

Medicity Research Laboratory,
University of Turku , Tykistokatu 6, FIN-20520 Turku , Finland . mersoi@utu.fi

Past sun exposure and vitamin D supplementation have been associated with a reduction in the risk of MS. We measured the serum concentration of 25-hydroxyvitamin D (25[OH]D) at the time of MS diagnosis in 40 MS patients and 40 controls. We found no difference in the serum levels of 25(OH)D between MS patients and controls when all samples or samples obtained during winter months were compared, but MS patients had significantly lower serum 25(OH)D concentrations in June to September than the controls. The vitamin D stores were adequate for bone metabolism (> 37 nmol/L) in 70% of MS patients throughout the year and within the hypovitaminosis level (< 37 nmol/L) in 30% of MS patients at some time of the year. During MS-relapses, 25(OH)D levels were lower than in remission, but mostly within the reference range observed in relation with normal bone metabolism. We conclude that the vitamin D stores in most MS patients are adequate for their normal bone metabolism. However, lower vitamin D levels during MS relapses than in remission suggest that vitamin D could be involved in the regulation of the clinical disease activity of MS. The optimal serum levels of vitamin D for the regulation of immune responses remain to be determined.

PMID: 15957505 [PubMed - indexed for MEDLINE]



Rev Neurol. 2005 Apr 1-15;40(7):394-6.

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[Seasonal variations in the outbreaks in patients with multiple sclerosis]

[Article in Spanish]

Abella-Corral J , Prieto JM , Dapena-Bolano D , Iglesias-Gomez S , Noya-Garcia M , Lema M .

Servicio de Neurologia, Hospital Clinico Universitario de Santiago de Compostela, A coruna,
Spain . javiabella@hotmail.com

INTRODUCTION: It has been suggested that there is an environmental factor at play in the aetiology and pathogenesis of multiple sclerosis (MS) that acts as an essential component of the disease process, and a number of studies also point to a relationship between the seasons of the year and the appearance of outbreaks. AIMS: Our aim was to study the possible relation between seasonal variations and the appearance of outbreaks in patients with relapsing-remitting forms of MS. PATIENTS AND METHODS: We studied 31 patients over the period between 1997 and 2002 and calculated the monthly and quarterly rate of incidence of outbreaks. The statistical evaluation of the results was performed by applying the Chi-squared test. RESULTS: We observed a higher incidence of outbreaks in the summer months (more in June) and a lower incidence in winter (less in December), with statistically significant differences. CONCLUSIONS: In our patients, outbreaks of MS are related to seasonal variations, with a higher number in the warmer months and fewer in the colder months.

PMID: 15849671 [PubMed - indexed for MEDLINE]



Neuroepidemiology. 2004 Sep-Oct;23(5):217-23.

Related Articles, Links

Seasonal variations in exacerbations and MRI parameters in relapsing-remitting multiple sclerosis.

Koziol JA , Feng AC .

Department of Molecular and Experimental Medicine, The Scripps Research Institute,
La Jolla , CA 92037 , USA . koziol@scripps.edu

Environmental factors may be involved in the etiology of multiple sclerosis (MS). We investigate prevalence of exacerbations and MRI findings in a cohort of relapsing-remitting multiple sclerosis patients, for evidence of seasonal variation or cyclic trends. We find only weak evidence of seasonality in our data. Differences in reports of seasonal variation in multiple sclerosis disease activity may be due to regional climatic differences or other geographic variables that change with latitude as well as genetic predisposition.




BMJ. 2005 Jan 15;330(7483):120. Epub 2004 Dec 7.

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Timing of birth and risk of multiple sclerosis: population based study.

Willer CJ , Dyment DA , Sadovnick AD , Rothwell PM , Murray TJ , Ebers GC ; Canadian Collaborative Study Group .

Department of Biostatistics,
University of Michigan , Ann Arbor , MI 48109 , USA .

OBJECTIVES: To determine if risk of multiple sclerosis (MS) is associated with month of birth in countries in the northern hemisphere and if factors related to month of birth interact with genetic risk. DESIGN: Population based study with population and family based controls and a retrospective cohort identified from death certificates. A post hoc pooled analysis was carried out for large northern datasets including
Sweden and Denmark . SETTING: 19 MS clinics in major cities across Canada (Canadian collaborative project on the genetic susceptibility to multiple sclerosis); incident cases of MS from a population based study in the Lothian and Border regions of Scotland; and death records from the UK Registrar General. POPULATIONS: 17,874 Canadian patients and 11,502 British patients with multiple sclerosis. MAIN OUTCOME MEASURE: Diagnosis of multiple sclerosis. RESULTS: In Canada (n = 17,874) significantly fewer patients with MS were born in November compared with controls from the population census and unaffected siblings. These observations were confirmed in a dataset of British patients (n = 11, 502), in which there was also an increase in the number of births in May. A pooled analysis of datasets from Canada , Great Britain , Denmark , and Sweden (n = 42,045) showed that significantly fewer (8.5%) people with MS were born in November and significantly more (9.1%) were born in May. For recent incident data, the effect of month of birth was most evident in Scotland , where MS prevalence is the highest. CONCLUSIONS: Month of birth and risk of MS are associated, more so in familial cases, implying interactions between genes and environment that are related to climate. Such interactions may act during gestation or shortly after birth in individuals born in the northern countries studied.


Med Hypotheses. 2005;64(3):608-18.

Related Articles, Links

Why we should offer routine vitamin D supplementation in pregnancy and childhood to prevent multiple sclerosis.

Chaudhuri A .

Department of Neurology, Institute of Neurological Sciences,
1345 Govan Road, Glasgow G51 4TF , UK . ac54@udcf.gla.ac.uk

Multiple sclerosis (MS) is a demyelinating disease of the central nervous system that runs a chronic course and disables young people. The disease is more prevalent in the geographic areas that are farthest from the equator. No form of treatment is known to be effective in preventing MS or its disabling complications. A number of epidemiological studies have shown a protective effect of exposure to sunlight during early life and a recent longitudinal study confirmed that vitamin D supplementation reduced life-time prevalence of MS in women. Very little is known regarding the role of vitamin D on the developing brain but experimental data suggest that cerebral white matter is vitamin D responsive and oligodendrocytes in the brain and spinal cord and express vitamin D receptors. It is possible that differentiation and axonal adhesion of oligodendrocytes are influenced by vitamin D level during brain development and a relative lack of vitamin D may increase oligodendroglial apoptosis. The age effect of migration on susceptibility to develop MS could be explained by a role of vitamin D on brain development. In areas of high MS prevalence, dietary supplementation of vitamin D in early life may reduce the incidence of MS. In addition, like folic acid, vitamin D supplementation should also be routinely recommended in pregnancy. Prevention of MS by modifying an important environmental factor (sunlight exposure and vitamin D level) offers a practical and cost-effective way to reduce the burden of the disease in the future generations.

Publication Types:

•  Review

PMID: 15617877 [PubMed - indexed for MEDLINE]


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