Effect of metabolic syndrome severity on cerebral haemodynamics and cognition in community-based cohort.

Background and aims: Metabolic syndrome (METS) increases the risk of cognitive decline, but its impact on cerebral haemodynamics remains unclear. This study investigated relationships between continuous metabolic syndrome severity score (cMETS), cerebral haemodynamics, and cognition.

Methods: In this cross-sectional study from the Epidemiology of Dementia in Singapore (EDIS) cohort, participants underwent neuropsychological assessments and arterial spin labelling MRI to evaluate cerebral haemodynamics, cognitive function, and composite metabolic syndrome severity (cMETS).

Results: The study included 602 older adults (median age 69, IQR 64-74; 54 % female). Associations between cMETS and cerebral haemodynamics were observed (CBF: β = 0.40, p < 0.001; sCoV: β = -0.65, p < 0.001). Post-hoc analysis revealed a paradoxical relationship: in the lowest tertile, higher CBF was associated with higher cMETS (β = 0.80, p = 0.004), whereas in the highest tertile, lower CBF was associated with higher cMETS (β = -1.17, p = 0.015). Higher cMETS was associated with poorer global cognition (β = -0.15, p = 0.011), particularly in visuoconstruction and visuomotor speed. CBF was positively associated with global cognition (β = 0.01, p < 0.001) and mediated 43.5 % and 26.2 % of the cMETS-cognition relationship in the lowest and highest tertiles, respectively.

Conclusion: These findings revealed associations of lower CBF specifically among individuals with higher cMETS. The observed mediation effect highlights the potential role of cerebral haemodynamics in the relationship between metabolic syndrome severity and cognitive performance. This demonstrates the complex interplay between metabolic factors and cerebral blood flow patterns in aging populations. Such nuanced associations warrant further investigation in longitudinal studies to better understand these relationships over time.