Cognitive decline is frequent in patients with multiple sclerosis (MS). The cognitive trajectory is not well understood and a global overview throughout the disease course needs to be elucidated. Besides, predictors of future cognitive decline are still needed.
We aim to (a) assess the temporal dynamics of cognitive function through disease course, and (b) explore different clinical and MRI predictors of cognitive decline in a large cohort of patients with MS.
Longitudinal study with 212 MS patients who performed a total of 605 neurological, cognitive and MRI examinations at different times of the disease [examinations per patient: 3 (IQR:2-3); baseline age: 40.2 (IQR:34.5-47.6) years; baseline disease duration: 8.2 (IQR:2.3-13.9) years]. A z-score for global cognition (z-BRB) and for each cognitive domain was obtained from the Rao's Battery, and a 3D-structural MRI was acquired to calculate regional gray matter (GM) volumes. We modelled the dynamics of cognition throughout the MS course using age at MS onset, education and sex adjusted mixed-effects linear spline models with knots at 5 and 15 years. An age and sex adjusted multivariate regression model was performed to determine which factors at the first examination best predict cognitive performance at last follow-up in the entire sample.
In the first 5 years of MS, we detected an increase in z-BRB (β=0.050, p=0.004) and z-attention (β=0.048, p=0.013), followed by a decline in z-BRB (β=-0.029, p=0.005) and z-verbal memory (β=-0.049, p=0.001) between the 5-15 years of the disease. During the 15-30 years of MS course, the cognitive decline was maintained, but also involved z-attention (β=-0.035, p=0.012). Lower education, higher EDSS and volumetric changes at right parahippocampus, left parsorbitalis, left superior, left middle and right inferior temporal, and right superior parietal areas at the first examination were associated with worse z-BRB at the last follow-up (adjR2=0.48, β=-0.652–0.863, p=<0.001–0.024).
In MS, cognition deteriorates after the first 5 years of the disease, with a steady decline over the next 25 years. The verbal memory is affected earlier and more markedly, followed by involvement of attention and information processing speed. Moreover, education, clinical disability and GM volume at baseline are associated with future cognitive outcomes.