Associations between systemic inflammation, neighborhood tree canopy, and white matter hyperintensities: The healthy brain initiative.

BackgroundSystemic inflammation is associated with greater white matter hyperintensities (WMH), increasing risk of Alzheimer's disease. Neighborhood greenspaces (e.g., parks) have been associated with reduced inflammation and dementia risk and fewer WMH.ObjectiveTo examine whether systemic inflammation and neighborhood % tree canopy are independently associated with and interact to influence WMH.MethodsWe used cross-sectional data on 161 participants with magnetic resonance imaging (MRI) in University of Miami's Healthy Brain Initiative who were ≥ 50-years old with no to mild cognitive impairment. U.S. Forest Service tree canopy data (2021) were used to derive tree canopy percentage per Census tract. High-sensitivity C-reactive protein (hs-CRP), a marker of systemic inflammation, was categorized as low/moderate (0-3 mg/L) and high (>3 mg/L). Total WMH volume was derived from structural MRI. Multivariable linear regression examined independent associations of hs-CRP and WMH and % tree canopy and WMH, and the association between a four-category hs-CRP-tree canopy variable (based on median cut points) and WMH.ResultsParticipants were 68.7 ± 9.3 years old and 70% were female. Higher hs-CRP was associated with greater WMH, and greater neighborhood % tree canopy was associated with fewer WMH. Compared to those with higher hs-CRP and lower % tree canopy, those with higher hs-CRP and greater % tree canopy had fewer WMH.ConclusionsHigher systemic inflammation and greater neighborhood % tree canopy were independently associated with WMH, and our findings suggest that they interact to influence WMH (e.g., in those with higher inflammation, having greater neighborhood tree canopy associated with lower WMH).