Leroi 2019.

Study characteristics
Methods	RCT
Participants	N = 61 Parkinson's disease dementia (PDD); dementia with Lewy bodies (DLB) according to standard clinical diagnostic criteria Median age (whole sample) 75 (range 55‐90) Community
Interventions	Individual cognitive stimulation adapted for Parkinson's disease (delivered by informal carers) (CST‐PD) (N = 31) Treatment‐as‐usual controls (N = 30)
Outcomes	Cognition: ACE‐III; Dementia Cognitive Fluctuation Scale Quality of Life: EQ‐5D; Parkinson's Disease Questionnaire‐39 Quality of relationship: Relationship Satisfaction Scale Mood: Hospital Anxiety & Depression Scale; Lille Apathy Rating Scale; Brief Resilience Scale ADL: The Pill Questionnaire (specific ADL task) Interpersonal Reactivity Index Behaviour problems: NPI Caregiver outcomes: Hospital Anxiety & Depression Scales; EQ‐5D; Short Form‐12 Health Survey (SF‐12); Relationship Satisfaction Scale; Dyadic Relationship Scale; Zarit Burden Interview; Relatives Stress Scale; Family Caregiving Role Scale; Brief Resilience Scale
Notes	30 minutes, 2‐3 times a week for 12 weeks Study also included mild cognitive impairment in Parkinson's disease (PD‐MCI); study authors have provided data for PDD and DLB separately for this review.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"an independent arbiter, applied a single‐stratum, blocked randomization to CST‐PD or TAU at a 1:1 level by participant–dyad".
Allocation concealment (selection bias)	Low risk	Independent process: "A tamper proof process of single‐strata, blocked randomisation will be applied and communicated via telephone and confirmatory email by an independent arbiter" (trial protocol).
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Clearly blinded:"'Procedures were in place to conceal the allocation from the independent, blinded outcome raters".
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	In the additional data provided by the study authors for e.g. the main cognition outcome (ACE‐III), 10/28 were missing at post‐treatment (cf. 3/28 for the control group). Analyses were for complete case only, so unclear what effect this might have
Selective reporting (reporting bias)	Low risk	Results for all outcomes were reported.
Other bias ‐ training and supervision	Low risk	Care partners received training and support to deliver the intervention.
Other bias ‐ treatment manual	Low risk	Manual developed (from iCST manual, Yates 2014) for the study