White matter lesion load is associated with lower within- and greater between- network connectivity across older age

White matter hyperintensities (WMH) are among the most prominent structural changes observed in older adulthood. These changes coincide with functional changes to the intrinsic network organization of the aging brain. Yet little is known about how WMH are associated with changes to the whole-brain functional connectome in normal aging. We used a lesion prediction algorithm to quantify WMH as well as resting-state multiecho functional magnetic resonance imaging to characterize resting-state functional connectivity in a cross-sectional sample of healthy older adults (N = 105, 60-83 years of age). In a multivariate analysis, we found that higher lesion load was associated with a global pattern of network dedifferentiation, marked by lower within- and greater between- network connectivity. Network specific changes included greater visual network integration and greater posterior-anterior connectivity. The relationship between WMH and resting-state functional connectivity was negatively associated with fluid IQ as well as Blood Oxygen Level Dependent signal dimensionality. Reduced functional network segregation is a widely observed pattern of age-related change. Our findings show that these functional changes are associated with the accumulation of WMH in older adulthood.