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Head injury is not a risk factor for multiple sclerosis: a prospective cohort study

Department of Neurology, Århus University Hospital, Aalborg, Denmark ccp{at}rn.dk

N Koch-Henriksen

Department of Neurology, Århus University Hospital, Aalborg, Denmark; The Danish Multiple Sclerosis Registry, Copenhagen, Denmark

E Stenager

The Danish Multiple Sclerosis Registry, Copenhagen, Denmark; Department of Neurology, Sønderborg Hospital, Region of Southern Denmark, Sønderborg, Denmark

EM Flachs

The Danish Multiple Sclerosis Registry, Copenhagen, Denmark; The National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark

C Johansen

The Danish Institute of Cancer Epidemiology, The Danish Cancer Society, Copenhagen, Denmark

Background

The idea of physical trauma being involved in the causation of multiple sclerosis (MS) had been discussed since the earliest description of the illness. Despite the ongoing debate, the proposed association between physical and especially head trauma and MS failed to be proved or to be refuted conclusively.

Objective

To determine whether head trauma is associated with an increased risk of developing MS.

Method

A cohort of 150,868 subjects, 95,111 men, and 55,757 women registered in the National Danish Patient Registry with hospital admission for cerebral concussion, contusion, or skull fracture between 1977 and 1992, aged under 55, was selected. This trauma cohort was linked with the Danish MS Registry and followed up to the end of 1999 to retrieve subjects who had onset of MS after the year of the head trauma. We calculated the expected number of subjects, who, under a null-hypothesis, would subsequently develop MS, by using population age-, year-, and sex-specific MS-incidence densities from the Danish MS Registry.

Results

For men and women combined, the observed to expected number of MS cases (possible cases included) with onset after the head injury was 182/193.6 (standardized incidence ratio [SIR], 0.94; 95% CI, 0.81–1.09) and for possible MS excluded, 171/164.7 (SIR, 1.04; 95% CI, 0.89–1.21). In an analysis of a sub-cohort of 16,425 subjects with severe trauma (contusion, traumatic cerebral hemorrhage, and base or skull fracture), the observed to expected numbers, including possible MS, were 15/15.3 (SIR, 0.98; 95% CI, 0.55–1.62) and with possible MS excluded, 13/12.9 (SIR, 1.01; 95% CI, 0.53–1.73). As for the total group and for any of the subgroups and for men and women separately, none of the SIRs differed statistically significantly from unity. Neither were there any trends, which could be missed by type II errors.

Conclusion

Head injury of any severity does not affect the risk of acquiring MS later in life.

Key Words: craniocerebral trauma • epidemiology • head injury • head trauma • multiple sclerosis • pathogenesis • trauma

This version was published on March 1, 2009

Multiple Sclerosis, Vol. 15, No. 3, 294-298 (2009)
DOI: 10.1177/1352458508099475


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