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MS research update - Can shift working put someone at increased risk of developing MS? - 24 February 2015

Summary

Working shifts disrupts the body's internal clock and so has an impact on normal body functions. In previous research it has been linked to increasing the risk of developing a wide variety of health problems including cardiovascular disease and cancer. This study looked at the effect of shift work on the risk of developing MS.

Participants in the Epidemiological Investigation of Multiple Sclerosis study in Sweden, were sent a questionnaire which contained a wide range of questions including a detailed set covering work.

The study found that working shifts before the age of 20 was associated with an increased risk of developing MS. There was also a higher risk for those who had done shift work for longer or had done shift work with more intense (more nights per month) shift patterns.

Although the study shows that there appears to be a relationship between doing shift work as a teenager and increased risk of developing MS, it cannot prove that prove that shift work is the reason.

Shift work affects the body in several ways including causing sleep deprivation and disruption to the body's natural 'clock' (circadian rhythm) that controls the cycle and rhythm of several body functions including hormone production and regulation of the immune system. The authors suggest these as areas that should be studied further to work out the way that shift work increases risk of developing MS.

Background

The cause of MS is not well understood, but it seems that genetic and environmental factors come together, to trigger MS in an individual.

Working shifts has an impact on normal life and normal body functions. It disrupts sleep and also the circadian rhythm which is the body's internal body clock, which not only tells us when to sleep and wake but also has control over many body functions including the immune system and hormone levels.

Previous research has shown that shift work is associated with a wide variety of health problems, increasing the risk of developing cardiovascular disease, cancer and autoimmune thyroid disorders. This study looked at the effect of shift work on the risk of developing MS.

How this study was carried out

The study used information from the Epidemiological Investigation of Multiple Sclerosis (EIMS) study. This is a study that began in 2004 and collects information from clinics around Sweden to investigate environmental and lifestyle factors that may cause MS or increase the risk of it developing. Each person with MS in the study is matched to two control participants, for age, gender and residential area. Participants are aged between 16 and 70 years old.

Participants were sent a questionnaire which contained a wide range of questions including a detailed set covering work. Completed questionnaires were returned from 2,337 people with MS and 4,904 control participants.

Shift work was defined as being a permanent or alternating working pattern that occurred between 9pm and 7am. The researchers looked at the information collected in several different ways to see if they could see any patterns between working and risk of developing MS. In the analysis age, gender, residential area, smoking habits, ancestry, ultraviolet exposure radiation (sunlight) exposure, educational level, relatives with MS, exposure to solvents, physical activity during adolescence, a history of glandular fever, and body mass index at age 20 were taken into account.

What was found

The study found that working shifts before the age of 20 was associated with an increased risk of developing MS. A similar relationship was found for participants who had started working shifts after the age of 20, but this was less pronounced. There was also a higher risk for those who had done shift work for longer or had done shift work with more intense (more nights per month) shift patterns.

People working shifts might be expected to be exposed to less sunlight due to their working patterns and consequently may have lower vitamin D levels. When the researchers looked at how much sunlight the participants reported being exposed to, participants with MS reported being exposed to less than controls. However there was no difference between people with MS who had done shift work and those that had not.

What does it mean?

The study shows that there appears to be a relationship between doing shift work as a teenager and increased risk of developing MS, so there appears to be some aspect in teenagers that is of importance. However the design of this study means, although it can show relationships it cannot prove that shift work is the reason for the results observed and how it causes an increased risk of MS. The authors do also say that as the study collected information from the participants through questionnaires many years in some cases after they were teenagers, they were relying on people's memories to give them accurate information.

The authors suggest several impacts that shift work could have on the body that could be studied further. These include sleep deprivation and disruption to the body's natural 'clock' (circadian rhythm) that controls the cycle and rhythm of several body functions including hormone production and regulation of the immune system.

Hedström A, Åkerstedt T, Olsson T, et al.
Shift work influences multiple sclerosis risk..
Mult Scler. 2015 Feb 19. pii: 1352458514563592. [Epub ahead of print]
abstract

More about the causes of MS

Almost 150 years after the condition was first recognised, the cause of MS remains a mystery. The theory that is widely held is that MS is an autoimmune disease - where the immune system, which should only target invading germs, turns on the body's own tissues. In the case of MS, the immune system attacks myelin, the fatty protein that covers nerves in the central nervous system.

The reason why the body reacts in this way is unknown but it is thought that the genetic make up of some people means that MS can be triggered by an environmental factor.

This current study has shown that the age at which someone started shift work is of importance to their risk of developing MS later in life. Teenagers are still growing and developing and it is known that shift work can affect several biological processes including the regulation of the immune system, so this is an area that should be researched further.

You can read more about the possible causes of MS in the A to Z of MS.

Research by topic areas...

Assessment tools

Zackowski KM, Wang JI, McGready J, et al.
Quantitative sensory and motor measures detect change over time and correlate with walking speed in individuals with multiple sclerosis.
Mult Scler Relat Disord. 2015 Jan;4(1):67-74.
abstract

Raggi A, Giovannetti AM, Schiavolin S, et al.
Development and validation of the multiple sclerosis questionnaire for the evaluation of job difficulties (MSQ-Job).
Acta Neurol Scand. 2015 Feb 18. [Epub ahead of print]
abstract

Bosnes O, Dahl OP, Almkvist O.
Including a subject-paced trial may make the PASAT more acceptable for MS patients.
Acta Neurol Scand. 2015 Feb 18. [Epub ahead of print]
abstract

Beckmann Y, Gürgör N, Çakır A, et al.
Electrophysiological evaluation of dysphagia in the mild or moderate patients with multiple sclerosis: a concept of subclinical dysphagia.
Dysphagia. 2015 Feb 17. [Epub ahead of print]
abstract

Carers

Buhse M, Ratta CD, Galiczewski J, et al.
Caregivers of older persons with multiple sclerosis: determinants of health-related quality of life.
J Neurosci Nurs. 2015 Apr;47(2):E2-E12.
abstract

Causes of MS

Motamed MR, Fereshtehnejad SM, Abbasi M, et al.
X-ray radiation and the risk of multiple sclerosis: Do the site and dose of exposure matter?
Med J Islam Repub Iran. 2014;28:145.
abstract
Read the full text of this paper

Diagnosis

Caucheteux N, Maarouf A, Genevray M, et al.
Criteria improving multiple sclerosis diagnosis at the first MRI.
J Neurol. 2015 Feb 17. [Epub ahead of print]
abstract

Disease modifying treatments

Le Page E, Deburghgraeve V, Lester MA, et al.
Alemtuzumab as rescue therapy in a cohort of 16 aggressive multiple sclerosis patients previously treated by Mitoxantrone: an observational study.
J Neurol. 2015 Feb 21. [Epub ahead of print]
abstract

Prosperini L, Annovazzi P, Capobianco M, et al.
Natalizumab discontinuation in patients with multiple sclerosis: Profiling risk and benefits at therapeutic crossroads.
Mult Scler. 2015 Feb 19. [Epub ahead of print]
abstract

Fragoso YD, Arruda CC, Arruda WO, et al.
The real-life experience with cardiovascular complications in the first dose of fingolimod for multiple sclerosis.
Arq Neuropsiquiatr. 2014 Sep;72(9):712-4.
abstract
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Economics

Wiberg M, Friberg E, Stenbeck M, et al.
Sources and level of income among individuals with multiple sclerosis compared to the general population: A nationwide population-based study.
Mult Scler. 2015 Feb 19. [Epub ahead of print]
abstract

Falls

Cameron M, Coote S, Sosnoff JJ.
Whom to target for falls-prevention trials: recommendations from the International MS Falls Prevention Research Network.
Int J MS Care. 2014 Winter;16(4):203-7.
abstract
Read the full text of this paper

Cattaneo D, Jonsdottir J, Coote S.
Targeting dynamic balance in falls-prevention interventions in multiple sclerosis: recommendations from the International MS falls Prevention Research Network.
Int J MS Care. 2014 Winter;16(4):198-202.
abstract
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Finlayson M, Cattaneo D, Cameron M, et al.
Applying the RE-AIM framework to inform the development of a multiple sclerosis falls-prevention intervention.
Int J MS Care. 2014 Winter;16(4):192-7.
abstract
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Gunn H, Cattaneo D, Finlayson M, et al.
Home or away? Choosing a setting for a falls-prevention program for people with multiple sclerosis.
Int J MS Care. 2014 Winter;16(4):186-91.
abstract
Read the full text of this paper

Coote S, Sosnoff JJ, Gunn H.
Fall incidence as the primary outcome in multiple sclerosis falls-prevention trials: recommendation from the International MS Falls Prevention Research Network.
Int J MS Care. 2014 Winter;16(4):178-84.
abstract
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Finlayson M, Peterson E, Matsuda PN.
Participation as an Outcome in Multiple Sclerosis Falls-Prevention Research: Consensus Recommendation from the International MS Falls Prevention Research Network.
Int J MS Care. 2014 Winter;16(4):171-7.
abstract
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Ploughman M, Deshpande N, Latimer-Cheung AE, et al.
Drawing on related knowledge to advance multiple sclerosis falls-prevention research.
Int J MS Care. 2014 Winter;16(4):163-70.
abstract
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Gender

Dunn SE, Lee H, Pavri FR, et al.
Sex-Based Differences in Multiple Sclerosis (Part I): Biology of Disease Incidence.
Curr Top Behav Neurosci. 2015 Feb 19. [Epub ahead of print]
abstract

Dunn SE, Gunde E, Lee H.
Sex-Based Differences in Multiple Sclerosis (MS): Part II: Rising Incidence of Multiple Sclerosis in Women and the Vulnerability of Men to Progression of this Disease.
Curr Top Behav Neurosci. 2015 Feb 19. [Epub ahead of print]
abstract

Physical activity

[No authors listed]
Poster Abstracts from the Fourth International Symposium on Gait and Balance in Multiple Sclerosis: The Role of CognitionCleveland Clinic • Cleveland, Ohio, USA • October 10 & 11, 2014.
Int J MS Care. 2014 Winter;16(4):209-10.
abstract
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Psychological aspects

Schreiber H, Lang M, Kiltz K, et al.
Is personality profile a relevant determinant of fatigue in multiple sclerosis?
Front Neurol. 2015;6:2.
abstract

Hancock LM, Bruce JM, Bruce AS, et al.
Processing speed and working memory training in multiple sclerosis: A double-blind randomized controlled pilot study.
J Clin Exp Neuropsychol. 2015 Feb 16:1-15. [Epub ahead of print]
abstract

Rehabilitation

Ilett P, Lythgo N, Martin C, et al.
Balance and Gait in People with Multiple Sclerosis: A Comparison with Healthy Controls and the Immediate Change after an Intervention based on the Bobath Concept.
Physiother Res Int. 2015 Feb 20. [Epub ahead of print]
abstract

Symptoms and symptom management

Čarnická Z, Kollár B, Šiarnik P, et al.
Sleep Disorders in Patients With Multiple Sclerosis.
J Clin Sleep Med. 2014 Dec 31. [Epub ahead of print]
abstract

Weiland TJ, Jelinek GA, Marck CH, et al.
Clinically Significant Fatigue: Prevalence and Associated Factors in an International Sample of Adults with Multiple Sclerosis Recruited via the Internet.
PLoS One. 2015;10(2):e0115541.
abstract
Read the full text of this paper

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