Table 1.

Data extraction table.

Researcher	Time	Country	Experimental group (PDD group)						Control group (PDND group)						Experimental group		Control group		PDD diagnostic criteria	Dementia evaluation method	Experimental method	Sample capacity (experimental group and control group ≥ 50)	Patient source	Average age	Literature quality
			2/2	2/3	2/4	3/3	3/4	4/4	2/2	2/3	2/4	3/3	3/4	4/4	ε4+	ε4−	ε4+	ε4−
Koller et al. [21]	1995	America	1	6	3	29	12	1	0	6	2	38	14	1	16	36	17	44	Calne criteria	DRS	Case-control study	Yes	Research center	PD67.4, PDD74.7	8
Harhangi et al. [22]	2000	Netherlands	1	8	1	7	9	0	0	14	2	51	13	1	10	16	16	65	Calne criteria	DSM	Cohort study	No	Community	PD75.8, PDD82.1	7
Wang et al. [30]	2001	China	0	1	0	6	4	0	0	1	0	35	4	0	4	7	4	36	Diagnostic criteria of National Symposium on Extrapyramidal Diseases in 1984	DSM	Case-control study	No	Hospital	PD66.13, PDD71.09	6
Zhou et al. [31]	2004	China	0	1	0	10	3	1	2	3	0	24	6	1	4	11	7	29	Diagnostic criteria of National Symposium on Extrapyramidal Diseases in 1984	DSM	Case-control study	No	Hospital	平均Averagely 67.4	6
Camicioli et al. [37]	2005	Canada													9	19	3	16	Pathology	DSM	Cohort study	No	Hospital	PD77.5, PDD78.1	7
Pankratz et al. [38]	2006	America													19	31	62	212	UK Brain Bank	MMSE	Case-control study	No	Community	Averagely 60.9	7
Troster et al. [39]	2006	America													9	11	11	31	Calne criteria	DRS	Case-control study	Yes	Research center	Averagely 68.6	7
Blazquez et al. [40]	2006	Spain													6	25	25	220	UK Brain Bank	MMSE	Case-control study	No	Hospital	Averagely 71.1	7
Ma [23]	2007	China	0	9	2	48	19	3	1	17	2	96	16	1	24	57	19	114	UK Brain Bank	DSM	Case-control study	No	Hospital	PD68.38, PDD69.72	8
Jasinska-Myga et al. [32]	2007	Poland	1	11	3	56	24	3	1	8	7	56	25	3	30	68	35	65	UK Brain Bank	DSM, MMSE	Case-control study	Yes	Hospital	PD61.7, PDD71.4	8
Tong [33]	2008	China	0	4	0	13	3	0	0	3	0	52	12	0	3	17	12	55	UK Brain Bank	DSM, MMSE	Case-control study	Yes	Hospital	PD70.35, PDD75.44	7
Ezquerra et al. [34]	2008	Spain	0	7	1	57	20	1	0	11	0	101	26	0	22	64	26	112	UK Brain Bank	PDD diagnostic criteria	Case-control study	No	Hospital	PD56, PDD58.3	7
Williams-Gray et al. [41]	2009	America													8	11	23	65	UK Brain Bank	DSM, MMSE	Cohort study	Yes	Community	Unknown	7
Irwin et al. [4]	2012	America													40	49	4	38	UK Brain Bank	DSM	Case-control study	No	Research center	PD80, PDD79	7
Wang [35]	2014	China	1	8	0	70	17	1	0	18	3	116	20	0	18	79	23	134	UK Brain Bank	PDD diagnostic criteria	Case-control study	No	Hospital	PD65.20, PDD67.95	8
Mengel et al. [36]	2016	Germany	0	12	3	34	22	1	5	56	9	222	81	2	26	46	92	283	UK Brain Bank	MDS-TFC	Case-control study	Yes	Research center	Averagely 66.7	6
Nicoletti et al. [42]	2016	Italy													13	12	12	12	UK Brain Bank	MMSE	Case-control study	Yes	Unknown	Averagely 64.7	8