White matter hyperintensity burden and post-stroke cognitive impairment: a systematic review and meta-analysis of clinically comparable estimates

Introduction White matter hyperintensity (WMH) burden is a common marker of cerebral small vessel disease and may identify stroke survivors with reduced cognitive reserve. Published estimates, however, use different imaging thresholds, cognitive definitions, follow-up periods, and effect measures. Methods We searched PubMed/MEDLINE, Embase, Web of Science Core Collection, and the Cochrane Library from database inception through 13 August 2026. We defined a principal clinically comparable estimand as an adjusted odds ratio comparing high/pathological WMH or white matter lesion burden with lower/normal burden for categorical post-stroke cognitive impairment. Ordinal, volumetric, regional, dementia-specific, and time-to-event estimates were retained in separate evidence strata. The protocol was registered on 16 April 2026 in PROSPERO (CRD420261367226). Results Twenty-one studies were included. Four studies contributed to the principal synthesis, which yielded an adjusted odds ratio of 2.87 (95% confidence interval 2.10–3.92; I 2 = 0%; τ 2 = 0; Q = 0.85). The modified Hartung–Knapp 95% confidence interval was 1.73–4.75, and leave-one-out estimates ranged from 2.72 to 3.10. Broader dichotomous, score-based, volumetric, vascular-dementia-specific, and time-to-event findings were directionally supportive but were not pooled with the principal estimand. Conclusion High/pathological WMH burden was associated with higher odds of post-stroke cognitive impairment in a small set of clinically comparable adjusted studies. WMH may help identify cognitive vulnerability after stroke, but current evidence does not support WMH as a causal factor or stand-alone prognostic test. Systematic review registration PROSPERO , CRD420261367226.