Asymptomatic carotid artery stenosis, cognitive decline and dementia: a prospective population-based cohort study

Background Asymptomatic carotid artery stenosis (ACAS) increases the risk of stroke, and is associated with cognitive decline. This association might be driven by underlying atherosclerotic disease instead of the stenosis itself, which could explain why studies on the cognitive benefits of carotid revascularisation are inconclusive. Methods Between 2007-2012, dementia-free participants of the population-based Rotterdam Study underwent carotid ultrasound, and additional carotid MRI if intimal media thickness was >2.5mm. All participants underwent repeated cognitive assessments and were followed for dementia until January 2022. We determined the effect of ACAS and plaque without stenosis on all-cause dementia using multivariable Cox models, and on change in cognition (g-factor) using multivariable linear mixed-effects models. Results Of 4267 participants (mean age 67.5 years, 55.5% women), 483 (11.3%) had plaque without stenosis, 989 (23.2%) had 1-49% stenosis, 107 (2.5%) had 50-99% stenosis, and 15 (0.4%) had occlusion. During a mean follow-up of 9.7 years, 391 participants developed dementia. Compared to individuals without carotid atherosclerosis, risk of dementia was increased in the presence of plaque without stenosis (HR: 1.39 [95%CI: 1.05-1.83]) and occlusion (HR: 4.61 [1.82-11.66]), but not with stenosis (HR 1-49% stenosis: 1.08 [0.84-1.39]; 50-99% stenosis: 1.18 [0.70-1.99]). Neither carotid plaques nor stenosis affected cognitive decline. Results did not differ consistently by plaque characteristics. Conclusion Risk of dementia was increased with asymptomatic carotid artery plaque and occlusion, but not significantly with 50-99% stenosis. These results are in line with detrimental effects of generalised atherosclerotic disease and severe haemodynamic impairment on cognitive decline and dementia risk.