TABLE 3.

Longitudinal studies

Citation	Samples characteristics, mean ± SD						Follow‐up period	Subtyping method	Cluster variables	Imaging method	Description of clusters (% prevalence)	Neuroimaging results
	N	Age, years	Education, years	Global cognition	Gender, % female	Disease duration, years
Andersson et al. (2021)	349 PD	63.6 ± 7.5	15.5 ± 3.0	NA	35%	0.5 ± 1.1	Annually for 5 years	Multivariate latent class linear mixed model	Composite scores used for each domain Memory: HVLT (immediate & delayed) Executive: SDMT, LNS, semantic fluency Visuospatial: JLO	NA	Class 1 (90%): gradual cognitive decline and worse performance on memory composite at baseline compared to controls Class 2 (10%): rapid cognitive decline and mild impairment on executive and memory composite at baseline; greater decline in memory and executive composites over time compared to Class 1	NA
Uribe et al. (2019), using Uribe et al. (2016) clusters	88 PD	60.4 ± 9.3	10.6 ± 4.8	MMSE: 29.0 ± 1.0	42%	8.0 ± 5.6	3.8 ± 0.4 years	Hierarchical clustering with Ward's method on cortical thickness data	Executive: phonemic and semantic fluency Memory: RAVLT (total & recall) Attention/working memory: digit span (forward & backward), Stroop (word, colour & word‐colour), SDMT, TMT (A, B, & A‐B) Language: BNT Visuospatial function: VFDT, JLO	3‐T structural MRI	See Uribe et al. (2016) Pattern 1: Parietotemporal atrophy and worse cognitive performance, particularly on semantic and episodic memory, and processing speed and attention/working memory Pattern 2: orbitofrontal cortical atrophy; decreases in processing speed, attention, and semantic fluency over time Pattern 3: patients without detectable cortical atrophy; decreases in processing speed, attention, and semantic fluency over time	High attrition rates (78%) for Pattern 1 prevented analysis on the neuroimaging or cognitive data Pattern 2 (55% attrition): subcortical grey matter atrophy over time. Reductions in left parahippocampal gyrus and precuneus and right inferior parietal and temporal gyri, fusiform and lateral occipital gyri thickness over time. No difference in cortical thickness decline compared to controls Pattern 3 (25% attrition): cortical grey matter atrophy over time. Cortical thinning of lateral and medial regions of temporal and parietal lobes, lateral occipital and extending to frontal regions such as the precentral and postcentral gyri and left pars opercularis. Increased cortical thinning in the left pars opercularis and precentral gyri over time compared to healthy controls

Abbreviations: BNT, Boston Naming Test; HVLT, Hopkin's Verbal Learning Test; JLO, Judgment of Line Orientation; LNS, Letter Number Sequencing; MMSE, Mini‐Mental State Examination; MRI, magnetic resonance imaging; NA, not applicable; PD, Parkinson disease; RAVLT, Rey Auditory Verbal Learning Test; SDMT, Symbol Digit Modality Test; TMT, Trail Making Test; VFDT, Visual Form Discrimination Test.