The study tested whether WMH accrue uniformly or as spatially patterned components. Applying nonnegative matrix factorization to T1/FLAIR scans from 1,836 SHIP participants (ages 22β84, median 52.2 y), the authors identified four components: periventricular frontal (WMHC-fron), posterior (WMHC-post), dorsal (WMHC-dors), and deep WMH. Half-split reproducibility showed 88% median overlap, and 66% overlap when components were re-derived from BLSA baseline (n=307), with the frontal component most stable (91%).
Frontal periventricular WMH became significant from the fifth decade (estimate 0.554 at 40β50 y vs 0.124β0.132 for other components), a decade earlier than all other components. Frontal WMH alone showed a significant systolic blood pressure association (estimate 0.006 per mm Hg, Bonferroni-corrected p=0.001) and more widespread cortical thinning including AD-related anterior temporal regions.
Only the dorsal periventricular component associated with the AD polygenic risk score in participants older than 65 (estimate 0.888, p=0.028 corrected, n=189) and, independently, with longitudinal cognitive decline in BLSA (747 observations, 16 mixed-effect models Bonferroni-corrected). This regional convergence is mechanistically plausible given postmortem evidence that posterior WMH in AD reflect cortical tau/amyloid-driven Wallerian degeneration rather than small vessel diseaseβWML area correlating with cortical AT8 (rho=0.289) and 4G8 (rho=0.289) pathology.
The authors honestly flag that components correlate highly with total WMH volume, leaving component-specific vs global-burden effects ambiguous; ~10% of SHIP participants did not conform to the staging model; several risk-factor associations lost significance after excluding 178 participants with possible cognitive impairment; and SHIP lacked complete cognitive testing. Independent falsification would require demonstrating that the four components fail to replicate with differential correlates in external cohortsβan open question, given the modest 66% SHIP-BLSA overlap outside the frontal component. This heterogeneity framing aligns with the wider literature: AD patients show only modestly elevated WML beyond aging (Fazekas effect ~0.16, equivalent to ~4.8 aging years), reinforcing that location, not merely burden, encodes etiology.
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