Size matters

Cortese M, Riise T, Bjørnevik K, Myhr KM; Multiple Sclerosis Conscript Service Database Study Group. Body size and physical exercise, and the risk of multiple sclerosis. Mult Scler. 2017: 1352458517699289

BACKGROUND: Whether large body size increases multiple sclerosis (MS) risk in men is not well understood. Concurrently, physical exercise could be an independent protective factor.

OBJECTIVE: To prospectively investigate the association between body mass index (BMI) and aerobic fitness, indicators of body size and exercise, and MS risk in men.

METHODS: We performed a population-based nested case-control study within the historical cohort of all Norwegian men, born in 1950-1975, undergoing mandatory conscription at the age of 19 years. 1016 cases were identified through linkage to the Norwegian MS registry, while 19,230 controls were randomly selected from the cohort. We estimated the effect of BMI and fitness at conscription on MS risk.

RESULTS: Higher BMI (≥25 vs 18.5-<25 kg/m2) was significantly associated with increased MS risk (adjusted relative risk (RRadj) = 1.36, 95% confidence interval (CI): 1.05-1.76). We also found a significant inverse association between aerobic fitness (high vs low) and MS risk independent of BMI (RRadj = 0.69, 95% CI: 0.55-0.88, p-trend = 0.003), remaining similar when men with MS onset within 10 years from conscription were excluded ( p-trend = 0.03).

CONCLUSION: These findings add weight to evidence linking being overweight to an increased MS risk in men. Furthermore, they suggest that exercise may be an additional modifiable protective factor for MS.

We have been talking about whether tallness makes a difference in accumulation of disability….I’m sure profG has an answer for this, but this study could perhaps of done it, instead it talks about Body mass index which is a mixture of weight and height. It says if you have a higher BMI you are at an increased risk of developing MS, which is not the same as reporting whether BMI affects the course. In this study it indicates a higher BMI is associated with an increased risk of MS. Likewise the more fit you were the less likely you were to develop MS.  This aspect is a modifiable risk factor however one can put an argument that maybe rather than cause it could be effect, so people with MS, pre-diagnosis MS may be more likely to be less fit and perhaps more sedantry leading to weight gain. So size matters..small is best.

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  • Mouse,

    I've seen you a couple of times at conferences and (forgive me for saying it) you are quite a big chap (in a "who ate all the pies" sort of way). You also mentioned on the blog that you were a smoker. As you spend lots of time in the lab / the inside of pubs, I don't imagine you are Vit D replete. Howe er, you are not an MSer. Perhaps this suggests that genes and an environmental factor are the big player in causing MS. My half aunt had Ms and I got mono as a teenager and I developed MS (I wasn't overweight, ran, got plenty of sun exposure and never smoked).

    • But as a youth I was playing outside every day until it got dark, I played football matches twice a week until i was in my 40s, football or other sports every day, I would walk miles to school or university including cycling 8 miles a day each way. Ceeded to peer pressure and started regular smoking later in life.

      Nobody in UK is vitamin D replete in Winter unless you have a sun holiday or you supplement and genes and environment are key in fact I was jeans size 29" inch waist until I got back problems, quit smoking and turned into size Lard.

      Susceptibility is spun early in your life…I was not the pie monster indeed:-( that you see.

    • Ouch, that was quite an exchange :-/

      Statistics are what they are – or maybe there is publication bias here as well because… say I want to write a paper on MS and obesity and my data shows NOTHING. Who would publish that? If I can torture my data until it confesses and shows something, then I get it published. Easier than doing experiments on mice.

    • The confidence interval only just crosses one, and the model doesn't adjust for other known risk factors for ms…. I think I'd agree with you, if I'd spent x years going through the effort of linking two large datasets I'd also invest the time in wrestling with the stats to get it publishable.

  • Given number of known professional athletes who developed MS, one could imagine that extreme body fitness is risk factor instead

      And recently a guy from Russian premier league soccer club appeared in local social network MS group (may be a fake but basic checks says against it…)
      I'm pretty sure I heard about others.
      There is not too much professional athletes out there to see so much of them affected.
      Free research idea! MS prevalence in professional sports compared to general population

    • Danny Wallace, etc,etc MS is common in the UK,it is going to happen, but also many people will not be diagnosed until they have gone from the limelight

    • MD, given your funny kuru-like inducting injections in the mouse model – does injury to the head raise the risk? Because that would be, maybe, more common in sports.
      Otherwise it's like you say, prevalence in the UK probably close to 200/100,000 poulation, which means that there would be many athletes… but even more teachers affected by MS 🙂

    • We have enough problems keeping the Home Office Sweet, if we were to induce head injury in the beasties, I'ld be having even more sleepless nights

    • Sleepless nights because i wuld be worrying what the Home Office would do and also because they have had us up all night checking them to see that they were OK, which they would not be because we would be disturbing them

  • "Likewise the more fit you were the less likely you were to develop MS." This has a very hollow ring to me, as does talk of BMI. I did a lot of cycling, walking, was always fit and active and as regards my weight, always borderline underweight. And I developed PPMS in my twenties.

  • At a general practice health assessment a couple of years ago I had the lowest QRISK score the nurse had ever seen

    making me officially the healthiest ill person in the practice – a dubious honour 😉

    Really can't see mass is an MS risk factor it would have been obvious enough by now if it was.

    Weight gain once mobility deteriorates is another matter and a horrible vicious downward spiral once it starts. Carrying more mass = more load transferring to the ground via your legs = harder to walk / stand / transfer. It ain't rocket science. To burn calories now have to use the upper body #thinkhand

  • But athletes end up developing MS, what does that mean then?
    What different, varied, and particular pro-inflammatory factors will trigger exacerbated immune responses?
    Vitamin D daily exposure or consumption in supplementation, genes and viruses have more to speak, otherwise any overweight, or obese person would develop MS. However, it is clear that maintaining a healthy diet can influence the recovery and decrease of symptoms, and avoid other comorbidities.
    Most of the people I know with MS were getting overweight after the onset of the disease exacerbated, when symptoms and sequelae became more disabling, given the fatigue, loss of mobility, etc.

  • I was no high profile athlete, but I was good enough to play in Venezuela internacional rugby team, trained very exposed to sunlight to the point of being sun burn most of the time…. A year after moving to Spain to finish my medical training I was diagnosed with MS. Luckily the neuro at the hospital I work offered me alemtuzumab after failing DMF. Sometimes I blame the reduced sunlight I took during that year (I was prepping a national exam) and training in the night as most clubs do in Europe, and sometimes I blame I got a HBV vaccine that I didn't neded a couple weeks prior to the onset, but the truth is nobody knows, and I have learn to accept that.

  • I think the incidence and prevalence of MS is low in Venezuela, so I would maybe look at your genes for answers – if you have ancestors from Europe, then that could explain something… otherwise it's just bad luck 🙁

    • I think its under-diagnosed, in my little bubble I knew a pair of cases… Most people in the Caribbean have ancestors from Europe, mostly from Spain, Italy and the UK… Bad luck getting MS, good luck getting it on 2015.

    • I totally agree with you that if one had the same number of MRI machines and neurologists per 100,000 population all around the world then MS epidemiology would look different :-).
      But it is also easy to see that some populations are more prone to MS than others – and it would be enough to be half or 1/4 Spanish for the risk to go up. Then moving to Europe further raises the risk.

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