Table 1.
Characteristics and outcomes of studies using cognitively impaired samples.
| Paper | Study Design | N | Age (years) | Condition | Quality Rating | Cognitive Measure | Vitamin C Measure | Outcome |
|---|---|---|---|---|---|---|---|---|
| Arlt, 2012 [37] | RCT | 23 | 60–80 | AD | 6 | MMSE, Word fluency, Immediate/delayed verbal recall, Trail-making task | CSF | 1000 mg/day of vit C and E (400 mg/day) increased CSF concentrations after 1 year, but decreased MMSE score and no effect on other measures |
| Galasko, 2012 [47] | RCT | 78 | 50–85 | AD | 4.5 | MMSE | CSF | Decline in MMSE score occurred in E/C/ALA group. (500 mg/day vit C, vit E, alpha lipoic acid) did not influence CSF biomarkers related to amyloid |
| Burns, 1989 [39] | RCT | 81 | ≥65 | Senile Dementia, Community dementia | 4.5 | MMSE | Blood tests | 200 mg Vit C, vits B1, B2, B3 No correlation between vit C intake and cognitive impairment |
| Bowman, 2009 [26] | Pros | 32 | 71 | AD | 5 | MMSE | CSF, plasma ascorbate | Neither Plasma nor CSF AA predictive of AD across 1 year |
| Zandi, 2004 [40] | Pros | 4740 (4540 healthy) | ≥65 | AD | 3.5 | 3MS, Dementia Questionnaire (DQ) | Supplement, Interview | vit E (>400 IU) and C (500 mg) supplements reduced the AD prevalence and incidence. Supplements alone had no protective affect across 2 years |
| Deijen, 2003 [41] | Pros | 90 | >65 | Psychiatry nursing home | 4.5 | Dutch geriatric nursing scale, Zorg Index geriatrie (ZIG) | Food record | Higher vitamin intakes were associated with a worse daily functioning across 6 months |
| Rinaldi, 2003 [42] | Cross | 141 | >70 | MCI, AD | 3 | Clinical dementia rating scale, MMSE, clock drawing test, Babcock story recall, auditory verbal learning test, Corsi block tapping test, Token test, category naming test, Oral word association test, visual search test, digit forward and backward test, Raven’s progressive colored matrices | Plasma ascorbate | Lower vit C concentrations in patients with AD and MCI. MCI sig lower then controls |
| Polidori, 2004 [43] | Cross | 141 | ≥65 | AD, VaD | 2 | MMSE | Plasma ascorbate | Plasma AA lower in AD and VD |
| Richardson, 2002 [44] | Cross | 37 | 65–97 | In-patient ward | 2 | MMSE | Plasma ascorbate | 75% with dementia had low concentrations of vitamin C |
| Lu, 2016 [45] | Cross | 2892 (768 MCI) | 58 | MCI | 2.5 | Montreal cognitive assessment | FFQ | Carotenoids, vit C, and vitamin B6 exhibited the highest protective factor loadings |
| Charlton, 2004 [46] | CC | 93 | ≥65 | Dementia | 4 | MMSE | Plasma Ascorbate/FFQ | Plasma AA lower in dementia, not explained by diet |
| Glaso, 2004 [47] | CC | 38 | 75–85 | AD | 4 | MMSE | Serum ascorbate/CSF | Both plasma vitamin C and CSF lower in AD. CSF: plasma AA ratio higher in AD |
| Riviere,1999 [48] | CC | 69 | >75 | Severe AD, Moderate AD, Hospitalised AD | 3.5 | MMSE | Plasma ascorbate, FFQ | Nutritional intake lower in Severe AD, plasma vit C lower in more severe AD, not explained by vit C intake |
| Masaki, 2000 [49] | CC | 3735 men | 71–93 | Dementia | 3 | Hasegawa scale, MMSE | Self-report supplementation | After controlling for factors such as age, education, stroke, there was an association with cognitive performance |
Key: MCI = Mild cognitive impairment, AD = Alzheimer’s, VaD = vascular dementia RCT = Randomized control trial, Pros = prospective, Cross = cross-sectional, CC = case-control, Vit = vitamin, FFQ = food frequency questionnaire, CSF = cerebrospinal fluid, MMSE = Mini mental state examination, 3MS = Modified Mini Mental State Examination, ALA = alpha lipoic acid.