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Table 1 Summary of characteristics of RCTs included in the systematic review

From: The preventive efficacy of vitamin B supplements on the cognitive decline of elderly adults: a systematic review and meta-analysis

First Author (Year) Country Participants Baseline levels of serum Hcy a (µmol/L) Characteristics of Participants Intervention Treatment
Duration
N(IG/CG)
ITT
Mean Age a (years)
(IG/CG)
Male (n/%)
(IG/CG)
Fei Ma (2019) China [28] 120 MCI patients aged ≥ 65 years with no terminal illness or mental disorders, recruited from communities 20.6 ± 2.2 60/60 69.2 ± 2.5/
68.5 ± 3.9
21(35.0)/
22(36.7)
folic acid 800 µg and vitamin B12 25 µg/day 6 months
Kwok Timothy
(2019) China [29]
279 MCI outpatients aged ≥ 65 years 13.8 ± 3.2 138/141 76.9 ± 5.4/
78.0 ± 5.3
87(63.1)/
79(56.1)
folic acid 400 µg and vitamin B12 500 µg/day 24 months
Fei Ma (2017)
China [30]
180 MCI patients aged ≥ 65 years with no terminal illness or mental disorders, recruited from communities 12.9 ± 4.4 90/90 74.8 ± 2.8/
74.6 ± 3.2
39(43.3)/
38(42.2)
folic acid 400 µg/day 24 months
Kwok Timothy
(2017) China [34]
271 diabetic non-demented outpatients aged ≥ 70 years 16.8 ± 5.7 137/134 74.7 ± 4.0/
75.8 ± 4.2
82(59.9)/
76(56.7)
vitamin B12 1000 µg/day 27 months
Cheng D (2016)
China [35]
104 elderly volunteers aged ≥ 55 years, recruited from communities or nursing homes 20.0 ± 5.6 57/47 74.3 ± 9.6/
72.5 ± 7.0
27(47.4)/
23(48.9)
folic acid 800 µg, vitamin B6 10 mg and vitamin B12 25 µg/day 14 weeks
Dangour AD
(2015) United Kingdom [36]
201 healthy volunteers aged ≥ 75 years 16.1 ± 4.3 99/102 79.9 ± 3.5/
80.1 ± 3.7
46(46.5)/
23(48.9)
vitamin B12 1 mg/day 12 months
van der Zwaluw NL (2014) Netherlands [37] 856 elderly participants aged ≥ 65 years with no dementia 14.2 ± 2.5 425/431 72.6 ± 5.7/
72.6 ± 5.8
244(57.0)/
255(59.0)
folic acid 400 µg and vitamin B12 500 µg/day 24 months
Hankey GJ (2013) Australia [26] 2214 patients with stroke or transient ischemic attack, MMSE ≥ 24 14.3 ± 8.5 1110/1104 63.6 ± 11.8 b 1491(67.3) folic acid 2 mg, vitamin B6 25 mg and vitamin B12 500 µg/day 3.4 years
Walker JG (2012) Australia [38] 900 elderly adults aged 60 ~ 74 years, recruited from communities 9.7 ± 2.7 447/453 65.9 ± 4.3/
66.0 ± 4.2
181(40.5)/
177(39.1)
folic acid 400 µg and vitamin B12 100 µg/day 24 months
de Jager CA (2012) United Kingdom [39] 266 MCI patients aged ≥ 70 years 11.5 ± 4.5 133/133 76.8 ± 5.1/
76.7 ± 4.8
40(36.4)/
40(35.4)
folic acid 0.8 mg, vitamin B12 0.5 mg and vitamin B6 20 mg/day 24 months
Ford AH (2010) Australia [40] 299 community-dwelling elderly men aged ≥ 75 years with hypertension 13.6 ± 5.3 150/149 79.3 ± 2.8/
78.7 ± 2.7
150(100)/
149(100)
folic acid 2 mg, vitamin B12 0.4 mg and vitamin B6 25 mg/day 24 months
van Uffelen JG (2008) Netherlands [41] 179 MCI patients aged 70 ~ 80 years, recruited from communities NR 90/89 75.4 ± 2.8/
74.9 ± 3.0
44(56.4)/
41(55.4)
folic acid 5 mg, vitamin B12 0.4 mg and vitamin B6 50 mg/day 12 months
Durga J (2007) Netherlands [42] 819 men and post-menopausal women aged 50 ~ 70 years 12.9 ± 2.4 406/413 60 ± 5/
60 ± 6
294(72)/
292(70)
folic acid 0.8 mg/day 3 years
McMahon JA (2006) New Zealand [43] 276 healthy participants aged ≥ 65 years 16.6 ± 4.9 138/138 73.6 ± 5.8/
73.4 ± 5.7
80(63.0)/
61(48.4)
folic acid 1 mg, vitamin B12 0.5 mg and vitamin B6 10 mg/day 2 years
Eussen SJ (2006) Netherlands [44] 131 elderly people aged ≥ 70 years with mild vitamin B12 deficiency 15.2 ± 5.1 66/65 83 ± 6/
82 ± 5
49(74.2)/
51(78.5)
folic acid 0.4 mg, vitamin B12 1 mg/day 6 months
Stott DJ (2005) United Kingdom [45] 47 elderly people aged ≥ 65 years with ischemic vascular disease 16.7 ± 6.5 23/24 72.6 ± 6.4/
72.8 ± 5.4
12(52.2)/
14(58.3)
folic acid 2.5 mg, vitamin B12 0.5 mg and vitamin B6 25 mg/day 3 months
Lewerin C (2005) Sweden [46] 195 community-dwelling participants 17.2 ± 5.2 126/69 75.7 ± 4.7/
75.6 ± 4.0
48(38.1)/
30(43.5)
folic acid 0.8 mg, vitamin B12 0.5 mg and vitamin B6 3 mg/day 4 months
Hvas AM (2004) Denmark [47] 140 elderly people with plasma methylmalonic acid 0.40 ~ 2.00µmol/L 13.2 c 70/70 75/74 c 20(28.6)/
22(31.4)
vitamin B12 1 mg/week 1 month
Garcia A (2004)
Canada [48]
24 community-dwelling participants aged ≥ 65 years, with an increased plasma methylmalonic acid and MMSE ≥ 24 12.2 ± 4.0 12/12 76/76 c 5(22.7) b vitamin B12 1 mg/month 6 months
Janet Bryan (2002)
Australis [49]
40 healthy older women aged 65 ~ 92 years, who did not smoke, were not pregnant or lactating NR 19/21 74.1 ± 5.75 b 0(0)/
0(0)
folic acid
750 µg/day
5 weeks
Fioravanti M (1998) Italy [50] 30 elderly patients aged 70 ~ 90 years, with memory complaints, MMSE score 16 ~ 24 and serum folate < 3 ng/ml, recruited from homes or communities NR 16/14 80.3 ± 5.8/
80.2 ± 5.5
4(25)/
1(7.1)
folic acid 15 mg/day 2 months
  1. Abbreviations: IG intervention group, CG control group, ITT Intention-To-Treat, NR not reported
  2. a Mean ± SD; b the combination of intervention group and control group; c the SD is unavailable