Multiple sclerosis clinical course and cardiovascular disease risk – Swedish cohort study

BACKGROUND AND PURPOSE: Cardiovascular disease (CVD) risk amongst multiple sclerosis (MS) patients appears raised, but few studies have examined CVD risk amongst an unselected MS patient group. MS course may be relevant for CVD risk. Our aim was to assess CVD risk and variation by course in MS patients. METHODS: The Multiple Sclerosis Register identified 7667 patients who received an MS diagnosis between 1964 and 2005. They were matched by age, period, region and sex with 76 045 members of the general population without MS using Swedish registers. Poisson regression compared the two cohorts to estimate the relative risk for CVD, overall, as well as grouped and individual CVD diagnoses. RESULTS: MS patients had an increased adjusted relative risk (with 95% confidence intervals; number of MS cohort events) for CVD of 1.31 (1.22-1.41; n = 847), with some variation by course: relapsing-remitting 1.38 (1.17-1.62; n = 168); secondary progressive 1.30 (1.18-1.53; n = 405) and primary progressive 1.15 (0.93-1.41; n = 108). The association for the relapsing-remitting course was not significant after excluding the first year of follow-up. Overall incidence rates per 1000 person-years for CVD are 11.8 (11.06-12.66) for the MS cohort and 8.8 (8.60-9.05) for the non-MS cohort. The most pronounced association was for deep vein thrombosis: relapsing-remitting 2.16 (1.21-3.87; n = 14), secondary progressive 3.41 (2.45-4.75; n = 52) and primary progressive 3.57 (1.95-6.56; n = 15). MS was associated with ischaemic stroke but largely during the first year of follow-up. MS was associated with a decreased relative risk for angina pectoris and atrial fibrillation. CONCLUSIONS: There is a significantly increased relative risk for CVD in MS, particularly for venous thromboembolic disorders in progressive MS, suggesting immobility as a possible factor. An increased frequency of ischaemic stroke in MS is most probably due to surveillance bias resulting from diagnostic investigations for MS. There is no increased relative risk for ischaemic heart disease in MS and atrial fibrillation appears to be less common than amongst the general population.