Spinal cord injury increases MS risk

Does spinal cord trauma increase your risk of getting MS? #MSBlog #MSResearch

"This study below suggests that people with spinal cord injury are more likely to develop MS than control subjects. This study is interesting, but needs to be reproduced as the conclusions are based on very few numbers (9 cases of spinal cord injury). Are there large enough data sets available to reproduce these results? Yes, I think there are. The Scandinavian, Kaiser-Permanente and the Veterans Administration databases may have sufficient data to look at this. It would also be worth looking at the NHS HES (hospital-episode statistics) database as well. Why is this important? A large number of MSers feel trauma has been involved in triggering their MS. At present the link between trauma, including neurotrauma, and MS is weak and a large number of us are worried about so called recall bias. In other words if you have a disease such as MS you are more likely to recall a significant recent event to which you ascribe a causal link. Recall bias is a big problem in most case-based epidemiological studies, particularly if they use retrospective (historical) methods. This is why prospective, non-biased studies are more convincing. 

The other issue is reverse causation; i.e. are people who are at risk of developing MS or who possibly have asymptomatic MS are increased risk of sustaining trauma? The is not a trivial issue. I have already mentioned in an earlier post this year that MS probably has a long asymptomatic period and during this time it could affect neurological functioning in subtle ways, for example it may slow down reflexes that protect you from having accidents. Therefore it is possible that the trauma is due to subtle alterations in neurological function that protect you from having accidents, an good example will be balance and righting reflexes. If these reflexes are not functioning optimally you are more likely to have falls. Reverse causation is an intractable problem, hence the need to be very careful about assigning causation to any association between two factors." 

Epub: Lin et al. Spinal cord injury is related to an increased risk of multiple sclerosis: a population-based, propensity score-matched, longitudinal follow-up study. J Neurotrauma. 2014.

Background: MS is a demyelinating autoimmune disease of the central nervous system (CNS). Trauma to CNS has been postulated to play a role in triggering CNS autoimmune disease. Although the association between traumatic brain injury and MS has been suggested in previous studies, epidemiological data on the association between spinal cord injury (SCI) and MS is still lacking. 

Aim: The aim of the present population-based, propensity score-matched, longitudinal follow-up study was therefore to investigate whether patients with SCI were at a higher risk of developing MS. 

Method: A total of 11913 subjects aged between 20 and 90 years with at least two ambulatory visits with the principal diagnosis of SCI in 2001 were enrolled in the SCI group. We used a logistic regression model that included age, sex, pre-existing comorbidities, and socioeconomic status as covariates to compute the propensity score. The non-SCI group consisted of 59565 propensity score-matched, randomly sampled subjects without SCI. Stratified Cox proportional hazard regression with patients matched by propensity score was used to estimate the effect of SCI on the risk of developing subsequent MS. 

Results: During follow-up, 5 subjects in the SCI group and 4 in the non-SCI group developed MS. The incidence rates of MS were 17.60 (95% confidence interval [CI], 5.71 to 41.0) per 100,000 person-years in the SCI group and 2.82 (95% CI, 0.77 to 7.22) per 100,000 person-years in the non-SCI group. Compared to the non-SCI group, the HR of MS for the SCI group was 8.33 (95% CI, 1.99 to 34.87, P =0.0037). 

Conclusion: Our study therefore shows that patients with SCI have an increased risk of developing MS.

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