Objective: To determine whether the burden of leukoaraiosis and the number of brain infarcts, defined by magnetic resonance imaging (MRI), are prospectively and independently associated with intraparenchymal hemorrhage (IPH) incidence in a pooled population-based study. Methods: Among 4,872 participants initially free of clinical stroke in the Atherosclerosis Risk in Communities Study and the Cardiovascular Health Study, we assessed white matter grade (range, 0-9), reflecting increasing leukoaraiosis, and brain infarcts using MRI. Over a median of 13 years of follow-up, 71 incident, spontaneous IPH events occurred. Results: After adjustment for other IPH risk factors, the hazard ratios (95% confidence intervals) across white matter grades 0 to 1, 2, 3, and 4 to 9 were 1.00, 1.68 (0.86-3.30), 3.52 (1.80-6.89), and 3.96 (1.90-8.27), respectively (p for trend <0.0001). These hazard ratios were weakened only modestly (p for trend = 0.0003) with adjustment for MRI-defined brain infarcts. The IPH hazard ratios for 0, 1, 2, or ≥3 MRI-defined brain infarcts were 1.00, 1.97 (1.10-3.54), 2.00 (0.83-4.78), and 3.12 (1.31-7.43) (p for trend = 0.002), but these were substantially attenuated when adjusted for white matter grade (p for trend = 0.049). Interpretation: Greater MRI-defined burden of leukoaraiosis is a risk factor for spontaneous IPH. Spontaneous IPH should be added to the growing list of potential poor outcomes in people with leukoaraiosis.
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