AbstractINTRODUCTIONWe aimed to investigate the association between white matter hyperintensity (WMH) shape and volume and the long‐term dementia risk in community‐dwelling older adults.METHODSThree thousand seventy‐seven participants (mean age: 75.6 ± 5.2 years) of the Age Gene/Environment Susceptibility (AGES)‐Reykjavik study underwent baseline 1.5T brain magnetic resonance imaging and were followed up for dementia (mean follow‐up: 9.9 ± 2.6 years).RESULTSMore irregular shape of periventricular/confluent WMH (lower solidity (hazard ratio (95% confidence interval) 1.34 (1.17 to 1.52), p < .001) and convexity 1.38 (1.28 to 1.49), p < .001); higher concavity index 1.43 (1.32 to 1.54), p < .001) and fractal dimension 1.45 (1.32 to 1.58), p < .001)), higher total WMH volume (1.68 (1.54 to 1.87), p < .001), higher periventricular/confluent WMH volume (1.71 (1.55 to 1.89), p < .001), and higher deep WMH volume (1.17 (1.08 to 1.27), p < .001) were associated with an increased long‐term dementia risk.DISCUSSIONWMH shape markers may in the future be useful in determining patient prognosis and may aid in patient selection for future preventive treatments in community‐dwelling older adults.