Shift work increases risk of MS

S

Hedström et al. Shift work at young age is associated with increased risk for multiple sclerosis. DOI: 10.1002/ana.22597. Article first published online: 17 OCT 2011



Objective: Environmental factors play a prominent role in MS aetiology. The aim of this study was to investigate the potential association between shift work and MS risk, which has previously never been investigated.

Methods: This report is based on 2 population-based, case–control studies, 1 with incident cases (1,343 cases, 2,900 controls) and 1 with prevalent cases (5,129 cases, 4,509 controls). The occurrence of MS among subjects who have been exposed to shift work at various ages was compared with that of those who have never been exposed.

Results: In both studies, there was a significant association between working shift at a young age and occurrence of MS (odds ratio (OR)*, 1.6; 95% CI, 1.2–2.1 in the incidence study and OR, 1.3; 95% CI, 1.0–1.6 in the prevalence study). In the incident study, the OR of developing MS was 2.0 (95% CI, 1.2–3.6) among those who had worked shifts for 3 years or longer before age 20 years, compared with those who had never worked shifts. The OR for the corresponding comparison in the prevalent study was 2.1 (95% CI, 1.3–3.4).

Interpretation: The observed association between shift work at a young age and occurrence of MS in 2 independent studies strengthens the notion of a true relationship. Consequences of shift work such as circadian disruption and sleep restriction are associated with disturbed melatonin secretion and enhanced proinflammatory responses and may thus be part of the mechanism behind the association.


* OR/odds ratio = the factor by which the risk is increased.

“I suspect that the link with shift work and MS risk is due to vitamin D deficiency; there is surprisingly little data on this. I feel an idea for a study coming on.”

“I also hypothesise that heavy Facebook users and gamers will also have lower vitamin D levels than non-Facebook users and non-gamers. This is a crisis waiting to happen unless we get vitamin D supplementation up the political agenda.”

About the author

Prof G

Professor of Neurology, Barts & The London. MS & Preventive Neurology thinker, blogger, runner, vegetable gardener, husband, father, cook and wine & food lover.

10 comments

  • I worked very early mornings in a grocers before going to school. I got glandular fever at 15, but my mother made me continue with the pre-school job as thought I was being a wimp. I suspect early shifts for teens weakens their immune system so they are more vulnerable to getting GF. My Vit D levels at this time were OK (ish) – outside sports etc.

  • Nice, clean-handed research. In what way has it expanded our knowledge of the origin of MS?

    I don't know how much it cost, nor who paid for it. But is was a clear waste of money.

    Why asking questions whose answers mean absolutely nothing? Why not searching the disease inside-out?

    Why not contemplating about the conclusion of the following research?

    http://www.ncbi.nlm.nih.gov/pubmed/20035511

    "The findings suggest that plaque formation has some basis other than destructive cell-mediated immunity directed against a myelin or oligodendrocyte antigen."

    Dr John Prineas has won the 2009 Charkot award, after all.

  • Re: "I worked very early mornings in a grocers before going to school. I got glandular fever at 15, but my mother made me continue with the pre-school job as thought I was being a wimp. I suspect early shifts for teens weakens their immune system so they are more vulnerable to getting GF. My Vit D levels at this time were OK (ish) – outside sports etc."

    I am not sure you can necessarily blame the work. I suspect shift work is simply an association and a marker for another risk factor that is causal. How do you know your vD levels were okay? Most people living in the UK (where did you grow up?) are deficient in vD at the end of winter unless they are on supplements.

  • Re: "In what way has it expanded our knowledge of the origin of MS?"

    Potentially a lot; causation theory is a complex science and you need to explain all observations.

    I suspect this association is due to vD deficiency, but could be wrong.

    A nice curved-ball to make you think when exploring alternative hypotheses. To quote Thomas Huxley: “The great tragedy of Science; the slaying of a beautiful hypothesis by an ugly fact.” May be the shift work data will slay one of your hypotheses?

  • We had met an experienced retired neurologist soon after diagnosis and one of the questions he asked was if there had been a period of disruption in sleep habits. So it probably isn't a new idea. I feel it's possible that sleep deprivation has a role independent of Vit D. (But please don't blame your mother Mr Anonymous)

  • I tend to agree that vitamin d would probably explain these findings but an alternative or complementary hypothesis may be melatonin. There is a current clinical trial going on. http://clinicaltrials.gov/ct2/show/NCT01279876

    It seems with MS research, a lot of it is just throwing food on the wall and seeing what sticks. This approach has a disavantage of showing a lot of spurious associations and dead ends but given the complex nature of this disease, there probably isn't a better way.

  • Re: "It seems with MS research, a lot of it is just throwing food on the wall and seeing what sticks."

    I good analogy, but this approach does give you some clues to the cause and how the risk factors may integrate.

  • Re: "complementary hypothesis may be melatonin"

    A very good point; somebody in group did due diligence on melatonin sometime back and the science was very interesting. We will see how it pans out.

  • Re "May be the shift work data will slay one of your hypotheses?"

    Aren't you surprised that MS fatigue resembles the "initialization" period of an abrupt early morning awakening, when the brain is struggling to get the extra oxygen needed for the day-mode through cerebral blood circulation?

    I was hoping for a comment on the research i posted earlier… the one co-written by Dr Prineas.

By Prof G

Translate

Categories

Recent Posts

Recent Comments

Archives