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Table 2 Summary of tDCS protocol of 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)

Type of intervention

Electrode size (cm2)

Intensity (mA)

Duration (minutes)

Number of session

Current density (mA/cm2) / Total charge density (mAh/cm2)

Anode

Cathode

Follow up duration (weeks)

Adverse effects

Andrade et al. (2022) [26]

Anodal + CS

25

2

30 (10 min for each area)

24 (3 sessions/ week, 2 months)

0.08 / 0.96

F5, CP5, F4 and F3, P4, P5

Contralateral supraorbital area

No

NR

Sham + CS

André et al. (2016) [19]

Anodal

35

2

20

4 consecutive day

0.06 / 0.08

Left-DLPFC (F3)

Right supraorbital area

2

No serious adverse events reported

Sham

Boggio (a) et al. (2009) [36]

Anodal

35

2

30

1

0.06 / 0.03

Left-DLPFC (F3)

Right supraorbital area

No

No serious adverse events reported

Sham

Boggio (b) et al. (2009) [36]

Anodal

35

2

30

1

0.06 / 0.03

Left temporal cortex (T7)

Right supraorbital area

No

No serious adverse events reported

Sham

Gonzalez et al. (2021) [32]

Anodal + CT

15

1.5

30

9 (3 sessions/ week, 3 weeks)

0.1 / 0.45

Left-DLPFC (F3)

Contralateral brachioradialis muscle

6

NR

Sham + CT

Gu et al. (2022) [22]

Anodal

35

2

20

5 consecutive days

0.06 / 0.10

Left temporal area (T3)

Right deltoid

4

No serious adverse events reported

Sham

Im et al. (2019) [24]

Bilateral

28.26

2

30

Every day for 6 months

0.07 / 6.37

Left-DLPFC (F3)

Right-DLPFC (F4)

No

NR

Sham

Khedr et al. (2019) [31]

Bilateral-anodal

35

2

40 (20 min for each side)

10 (5 sessions/week, 2 weeks)

0.06 / 0.38

T3-P3 and T4-P4

Left deltoid

No

No serious adverse events reported

Sham

Khedr (a) et al. (2014) [20]

Anodal

24

2

25

10 consecutive days

0.08 / 0.35

Left-DLPFC (F3)

Right supraorbital area

4 and 8

No serious adverse events reported

Sham

Khedr (b) et al. (2014) [20]

Cathodal

24

2

25

10 consecutive days

0.08 / 0.35

Right supraorbital area

Left-DLPFC (F3)

4 and 8

No serious adverse events reported

Sham

Liao et al. (2021) [35]

Anodal + Tai Chi

35

2

20

36 (3 sessions/week, 12 weeks)

0.06 / 0.69

Left-DLPFC (F3)

Right supraorbital area

No

No serious adverse events reported

Sham + Tai Chi

Liu (a) et al. (2020) [37]

Bilateral-anodal

35

2

20

1

0.06 / 0.02

Left DLPFC (F3) and right DLPFC (F4)

Inion (Iz)

No

No a serious dverse events reported

Sham

Liu (b) et al. (2020) [37]

Bilateral-anodal

35

2

20

1

0.06 / 0.02

Left temporal cortex (T3) and right temporal cortex (T4)

Inion (Iz)

No

No serious adverse events reported

Sham

Lu et al. (2019) [30]

Anodal + WMT

35

2

20

12 (3 sessions/week, 4 weeks)

0.06 / 0.23

Left lateral temporal cortex (LTC)

Contralateral upper limb

4 and 8

3 cases had transient skin sensation of tingling and burning induced by tDCS without producing any sustainabel effects

Sham + WMT

Anodal + CCT

Manor et al. (2018) [33]

Anodal

35

2

20

10 (5 sessions/week, 2 weeks)

0.06 / 0.19

Left-DLPFC (F3)

Right supraorbital area (Fp2)

No

No serious adverse events reported

Sham

Martin et al. (2019) [29]

Anodal + CT

35

2

30

15 (3 sessions/week, 5 weeks)

0.06 / 0.43

Left-DLPFC (F3)

F8

12

No serious adverse events reported

Sham + CT

Rasmussen et al. (2021) [28]

Anodal

12 mm in diameter (HD-tDCS)

2

20

6 (3 sessions/day, 2 days)

1.80 / 3.33

Left-DLPFC (F3)

Surrounded anodal electrode

No

No serious adverse events reported

Sham

Rodella et al. (2022) [21]

Anodal + CT

16

2

30

12 (3 sessions/week, 4 weeks)

0.125 / 0.75

Left-DLPFC (F3)

Right deltoid

24

NR

Sham + CT

Smirni (a) et al. (2021) [34]

Cathodal + Phonemic fluency task

35

1

20

1

0.03 / 0.01

Contralateral shoulder

Left-DLPFC (F3)

No

NR

Sham + Phonemic fluency task

Smirni (b) et al. (2021) [34]

Cathodal + Phonemic fluency task

35

1

20

1

0.03 / 0.01

Contralateral shoulder

Right-DLPFC (F4)

No

NR

Sham + Phonemic fluency task

Stonsaovapak et al. (2020) [23]

Anodal

25

2

20

12 (3 sessions/week, 4 weeks)

0.08 / 0.32

Right-DLPFC (F4)

Left supraorbital area

4

The most common side effect is a tingling sensation

Sham

Suemoto et al. (2014) [25]

Anodal

35

2

20

6 (3 sessions/week, 2 weeks)

0.06 / 0.11

Left-DLPFC (F3)

Right orbit

1

The minor side effects; tingling, scalp burning, skin redness, somnolence, headache, and scalp pain were more common in the anodal compared to sham group

Sham

Xu (a) et al. (2023) [27]

Anodal + Tai Chi

0.9

2

20

36 (3 sessions/week, 12 weeks)

2.22 / 26.67

Right-DLPFC (F4)

Supraorbital (Fp1)

No

NR

Sham + Tai Chi

Xu (b) et al. (2023) [27]

Anodal + walking

0.9

2

20

36 (3 sessions/week, 12 weeks)

2.22 / 26.67

Right-DLPFC (F4)

Supraorbital (Fp1)

No

NR

Sham + walking

  1. The current density and total charge density were computed by using the following calculations [38];
  2. Current density (mA/cm2) = Current (mA) \(\div\) electrode size (cm2)
  3. Charge (mAh) = Current (mA) \(\times\) tDCS duration (minutes) \(\div\) 60
  4. Charge Density (mAh/cm2) = Charge (mAh) \(\div\) electrode size (cm2)
  5. Total Charge Density (mAh/cm2) = Charge Density (mAh/cm2) \(\times\) tDCS sessions
  6. CCT Control cognitive training, CS Cognitive stimulation, CT Cognitive training, DLPFC Dorsolateral prefrontal cortex, NR not reported, WMT Working memory training
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Alzheimer's Research & Therapy

ISSN: 1758-9193