A systematic review and meta-analysis of the impact of transcranial direct current stimulation on cognitive function in older adults with cognitive impairments: the influence of dosage parameters

Prathum, Thatchaya; Chantanachai, Thanwarat; Vimolratana, Oranich; Laksanaphuk, Chotica; Apiworajirawit, Irin; Aneksan, Benchaporn; Latthirun, Kanthika; Yang, Cheng-Ta; Klomjai, Wanalee

doi:10.1186/s13195-025-01677-y

Alzheimer's Research & Therapy

Table 1 The characteristics of the included studies

From: A systematic review and meta-analysis of the impact of transcranial direct current stimulation on cognitive function in older adults with cognitive impairments: the influence of dosage parameters

Study (year)	Sample size	Design	Diagnosis	Gender (F / M)	Age (y)	Education (y)	Duration of disease (y)	Cognitive domain	Cognitive measures
Andrade et al. (2022) [26]	NE: 18	Parallel	AD	8 / 10	75.4 ± 4.7	4.4 ± 2.7	1.2 ± 0.4	Global cognition	ADAS-Cog
Andrade et al. (2022) [26]	NC: 18	Parallel	AD	9 / 9	77.1 ± 5.2	5.6 ± 3.1	1.3 ± 0.4	Global cognition	ADAS-Cog
André et al. (2016) [19]	NE: 13	Parallel	VD	NR	80.3 ± 5.8	NR	NR	Global cognition, Working memory, Memory, Executive function	ADAS-Cog, 2-back test, PNT, Go-no go task
André et al. (2016) [19]	NC: 8	Parallel	VD	NR	75.8 ± 7.4	NR	NR		ADAS-Cog, 2-back test, PNT, Go-no go task
Boggio et al. (2009) [36]	NE: 10	Crossover	AD	6 / 4	79.1 ± 8.8	NR	NR	Working memory, Executive function, Memory	FDS, BDS, Stroop test, VRM
Boggio et al. (2009) [36]	NC: 10	Crossover	AD	6 / 4	79.1 ± 8.8	NR	NR	Working memory, Executive function, Memory	FDS, BDS, Stroop test, VRM
Gonzalez et al. (2021) [32]	NE: 21	Parallel	MCI	15 / 6	69.8 ± 5.3	9.7 ± 3.6	NR	Global cognition, Working memory, Everyday memory skill, Memory, Attention/processing speed, Executive function	MoCA, FDS, BDS, RBMT, Non-adaptive task, TMT-A, TMT-B
	NCa: 24			16 / 8	71.0 ± 6.2	9.7 ± 3.6
	NCb: 21			17 / 4	70.6 ± 5.4	11.9 ± 4.9
Gu et al. (2022) [22]	NE: 20	Parallel	MCI	7 / 13	63.2 ± 7.0	11.2 ± 3.0	NR	Global cognition, Overall memory, Memory	MoCA, MQ, WMS
Gu et al. (2022) [22]	NC: 20	Parallel	MCI	11 / 9	65.2 ± 6.2	9.9 ± 3.2	NR	Global cognition, Overall memory, Memory	MoCA, MQ, WMS
Im et al. (2019) [24]	NE: 11	Parallel	AD	10 / 1	71.9 ± 9.2	6.3 ± 3.8	NR	Global cognition, Working memory, Memory, Executive function, Language, Visuospatial processing	MMSE, FDS, BDS, RCFT, SVLT, COWAT, Go-no go Test, Stroop Test, BNT, Clock Drawing Test
Im et al. (2019) [24]	NC: 7	Parallel	AD	5 / 2	74.9 ± 5.0	5.4 ± 5.9	NR
Khedr et al. (2019) [31]	NE: 23	Parallel	AD	10 / 13	64.2 ± 3.6	4.0 ± 2.8	14.1 ± 5.8	Global cogntion, Visuospatial processing	MMSE, MoCA, Clock drawing test
Khedr et al. (2019) [31]	NC: 21	Parallel	AD	8 / 13	65.2 ± 4.5	3.5 ± 2.0	14.1 ± 4.7	Global cogntion, Visuospatial processing	MMSE, MoCA, Clock drawing test
Khedr et al. (2014) [20]	NEa: 11	Parallel	Dementia	5 / 6	68.5 ± 7.2	NR	3.0 ± 2.6	Global cognition	MMSE
	NEb:12			4 / 8	70.7 ± 5.4		2.9 ± 1.9
	NC: 11			6 / 5	67.3 ± 5.9		3.5 ± 1.7
Liao et al. (2021) [35]	NE: 10	Parallel	MCI	8 / 2	72.6 ± 4.1	8.5 ± 3.6	NR	Global cognition, Working memory, Executive function, Attention/precessing speed, Memory	MoCA, VWM, ToL, TMT-B, Stroop test, TMT-A, CVVLT
Liao et al. (2021) [35]	NC: 10	Parallel	MCI	5 / 5	73.1 ± 4.6	12.1 ± 2.9	NR		MoCA, VWM, ToL, TMT-B, Stroop test, TMT-A, CVVLT
Liu et al. (2020) [37]	NE: 17	Crossover	AD or mixed AD/VD	7 / 10	77 ± 5	16 ± 3	NR	Global cognition, Working memory	ADAS-Cog, MoCA, 2-back test
Liu et al. (2020) [37]	NC: 17	Crossover	AD or mixed AD/VD	7 / 10	77 ± 5	16 ± 3	NR	Global cognition, Working memory	ADAS-Cog, MoCA, 2-back test
Lu et al. (2019) [30]	NEa: 69	Parallel	AD	42 / 21	74.2 ± 6.7	7.3 ± 4.8	NR	Global cognition, Working memory, Memory, Neuropsychiatric symptoms, Attention/processing speed, Executive function, Verbal fluency	ADAS-Cog, MMSE, N-back test, FDS, BDS, word list learning task-delayed recall, NPI, TMT-A, TMT-B, CVFT,
	NEb: 68			30 / 27	73.4 ± 6.1	7.5 ± 5.3
	NC: 64			36 / 17	74.5 ± 6.6	6.5 ± 4.3
Manor et al. (2018) [33]	NE: 9	Parallel	Executive dysfunction	5 / 4	82 ± 4	NR	NR	Global cognition, Executive function	MoCA, TMT
Manor et al. (2018) [33]	NC: 9	Parallel	Executive dysfunction	5 / 4	79 ± 4	NR	NR	Global cognition, Executive function	MoCA, TMT
Martin et al. (2019) [29]	NE: 33	Parallel	MCI	20 / 13	71.8 ± 6.4	14.5 ± 3.5	NR	Memory, Learning, Attention/processing speed, Cognitive failures	CVLT, CANTAB-PAL, CANTAB-RVIP, Symbol Digit Modalities Test, Choice Reaction Time, CFQ
Martin et al. (2019) [29]	NC: 35	Parallel	MCI	25 / 10	71.6 ± 6.4	14.9 ± 3.2	NR
Rasmussen et al. (2021) [28]	NE: 10	Parallel	AD	9 / 1	69.2 ± 5.9	NR	NR	Global cognition, Visuospatial processing, Attention/processing speed	MMSE, RBANS, Clock-drawing test, TMT-A
Rasmussen et al. (2021) [28]	NC: 9	Parallel	AD	5 / 4	76.3 ± 6.8	NR	NR		MMSE, RBANS, Clock-drawing test, TMT-A
Rodella et al. (2022) [21]	NE: 13	Parallel	MCI/AD	5 / 8	71.6 ± 5.7	11.1 ± 5.0	NR	Global cognition, Working memory, Memory, Executive function, Attention/processing speed, Visuospatial function	MMSE, Digit Span, Verbal span, Corsi’s block-tapping test span, Logical Memory Test, Rey's 15 words test, RCFT-delayed recall, Raven’s Matrices 1947, FAB, Attentive Matrices, TMT-A, TMT-B, RCFT-copy
Rodella et al. (2022) [21]	NC: 15	Parallel	MCI/AD	6 / 9	75.1 ± 4.8	9.7 ± 5.0	NR
Smirni et al. (2021) [34]	NE: 20	Parallel	AD	14 / 6	73.4 ± 5.7	12.8 ± 3.4	NR	Verbal fluency	Phonemic Fluency Tasks
Smirni et al. (2021) [34]	NC: 20	Parallel	AD	13 / 7	73.0 ± 5.6	12.7 ± 3.7	NR	Verbal fluency	Phonemic Fluency Tasks
Stonsaovapak et al. (2020) [23]	NE: 23	Parallel	MCI	21 / 2	68.4 ± 8.4	NR	NR	Attention/ processing speed, Working meory, Memory	CANTAB; RVIP, SWM, DMS, PRM
Stonsaovapak et al. (2020) [23]	NC: 22	Parallel	MCI	20 / 2	69.7 ± 7.6	NR	NR	Attention/ processing speed, Working meory, Memory	CANTAB; RVIP, SWM, DMS, PRM
Suemoto et al. (2014) [25]	NE: 20	Parallel	AD	15 / 5	79.4 ± 7.1	5.0 ± 4.2	NR	Global cognition, Learning, Attention/processing speed, Memory, Neuropsychiatric symptoms	ADAS-Cog, word-list learning task, Digit cancellation task, word recognition task, NPI
Suemoto et al. (2014) [25]	NC: 20	Parallel	AD	13 / 7	81.6 ± 8.0	4.5 ± 3.9	NR
Xu et al. (2023) [27]	NEa: 44	Parallel	MCI	32 / 12	59 [8.75]	9.5 [3.8]	NR	Global cognition, Overall memory, Memory, Executive function, Attention/processing speed	MoCA, MQ, AVLT, ROCF, Stroop test, TAP
	NEb: 44			23 / 21	63 [12.75]	9 [5]
	NCa: 49			30 / 19	61 [8.5]	9 [4]
	NCb: 43			26 / 17	58 [8]	9 [4]

Data are expressed as mean ± SD or median [IQR]. Independent studies in the same literature are distinguished by (a) and (b)
AD Alzheimer’s disease, ADAS-Cog Alzheimer's Disease Assessment Scale–Cognitive, AVLT Auditory-verbal learning test, BDS Backward digit span, CANTAB Cambridge Neuropsychological Test Automated Battery, CFQ Cognitive Failures Questionnaire, COWAT Control Oral Word Association Test, CVFT Category verbal fluency test, CVLT California Verbal Learning Task, CVVLT Chinese Version of the Verbal Learning Test, FAB Frontal Assessment Battery, FDS Forward digit span, MCI Mild Cognitive Impairment, MMSE Mini-Mental State Examination, MoCA Montreal Cognitive Assessment, MQ Memory quotient, NE number of experimental group, NC number of control group, NPI Neuropsychiatric Inventory, NR not reported, PAL Paired Associates Learning, PNT Picture Naming Task, RBANS Repeatable Battery for the Assessment of Neuropsychological status, RBMT Rivermead Behavioral Memory Test, RCFT Rey Complex Figure Test, ROCF Rey-Osterrieth Complex Figure, RVIP Rapid Visual Information Processing, SVLT Seoul Verbal Learning Task, SWM Spatial Working Memory, DMS Delayed Matching to Sample, PRM Pattern Recognition Memory, TAP Test of Attentional Performance, TMT Trial Making Test, ToL Tower of London task, VD Vascular Dementia, VRM Visual Recognition Memory task, VWM Visual working memory, WMS Wechsler Memory Scale-Revised of China, y number of year, F / M Female / Male

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