Vascular risk factors are associated with grey matter atrophy in secondary progressive multiple sclerosis

Background: Comorbidities including vascular risk factors can be associated with whole and regional brain atrophy in multiple sclerosis (MS). This has been examined in mixed MS cohorts in prospective or observational studies; however, the association between vascular comorbidities (VCM) in secondary progressive MS (SPMS) and brain atrophy has been less well studied. The aim was to investigate the cross-sectional and longitudinal association between VCM, comorbidity burden and brain atrophy in SPMS. Methods: Post hoc analysis of 445 participants from the MS-Secondary Progressive multi-arm trial (MS-SMART)-a multi-arm multicentre phase-2b randomised placebo-controlled trial of three agents in SPMS (NCT01910259). VCM (hypertension, hyperlipidaemia) but also asthma, hypothyroidism and osteoporosis were recorded. Regional and whole brain volume (WBV), and percentage brain volume change were calculated using SIENAX and SIENA, respectively. Multiple linear regression was used to investigate the cross-sectional and longitudinal relationships between VCM, overall comorbidity count and whole brain, grey matter (GM) and white matter (WM) atrophy. Results: The cohort was predominantly female (67%), mean age 55 with median EDSS 6.0. In total, 13% and 9% had hypertension and hyperlipidaemia, respectively. In cross-sectional regression models, VCM was associated with decreased cortical GM volume [(hypertension β = -0.30, 95%CI -0.54 to -0.06, p = 0.01) (hyperlipidaemia β = -0.37, 95%CI -0.64 to -0.09, p = 0.008)]; but not WBV. Having ≥2 comorbidities was also associated with decreased cortical GM volume (β = -0.36, 95%CI -0.61 to -0.10, p = 0.007). No relationship was observed between VCM/comorbidity count and whole brain or GM atrophy rate over 96 weeks. Conclusions: People with SPMS with VCM or increased overall comorbidity burden showed reduced whole brain and especially cortical grey matter volumes, but no significant impact on subsequent 2-year atrophy rate was detected.