In most cases, motor symptoms predominate at early PD stages, while cognitive disturbances (such as mild cognitive impairment or dementia) emerge later.[11] The onset of parkinsonism in PD relative to dementia is used as an arbitrary criterion to clinically distinguish Parkinson's disease dementia (PDD) and dementia with Lewy bodies (DLB) using a ‘one-year rule’.[11] Dementia onset within 12-months of or at the same time as motor dysfunctions qualified as DLB, whereas in PDD, parkinsonism had to precede dementia by at least one year.[11]