Summary of findings for the main comparison. B vitamins compared to placebo for MCI.
B vitamins compared to placebo for MCI | |||||
Patient or population: MCI Setting: community Intervention: B vitamins (B6, B12, folic acid) Comparison: placebo | |||||
Outcomes | Anticipated absolute effects* (95% CI) | № of participants (studies) | Certainty of the evidence (GRADE) | Comments | |
Risk with placebo | Risk with B vitamins | ||||
Incidence of dementia ‐ not measured | ‐ | ‐ | ‐ | ‐ | |
Overall cognitive function assessed with: MMSE Scale from: 0 to 30 follow‐up: range 6 months to 24 months | MD with B vitamins was 0.44 MMSE points higher (0.23 lower to 1.12 higher) than with placebo * | 488 (3 RCTs) | ⊕⊝⊝⊝ VERY LOW 1 2 3 | Due to the very low‐quality of the evidence, we cannot be sure of any effect of B vitamins on overall cognitive function. * 2 studies reported final score; 1 study reported change from baseline. From the 2 studies (n=150) which reported final scores, the mean MMSE with placebo was 26.97 points. |
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Episodic memory assessed with: various word list recall instrumentsa follow‐up: range 6 months to 24 months | SMD with B vitamins was 0.09 higher (0.1 lower to 0.29 higher) than with placebo | 397 (3 RCTs) | ⊕⊕⊕⊝ MODERATE 3 | B vitamins probably resulted in little to no difference in episodic memory. | |
Executive function assessed with: various instrumentsb follow‐up: range 6 months to 24 months | SMD with B vitamins was 0.03 higher (0.23 lower to 0.29 higher) than with placebo | 392 (3 RCTs) | ⊕⊕⊕⊝ MODERATE 4 | B vitamins probably resulted in little to no difference in executive function. | |
Speed of processing assessed with: various instrumentsc follow‐up: range 6 months to 24 months | SMD with B vitamins was 0.04 higher (0.26 lower to 0.34 higher) than with placebo | 173 (2 RCTs) | ⊕⊕⊕⊝ MODERATE 4 | B vitamins probably resulted in little to no difference in speed of processing. | |
Quality of life assessed with: D‐QOL Scale from: 1 to 5 follow‐up: 12 months | The mean quality of life was 3.5 points | MD 0 points (0.1 lower to 0.1 higher) | 138 (1 RCT) | ⊕⊕⊕⊝ MODERATE 5 | B vitamins probably resulted in little to no difference in quality of life. |
Mortality ‐ not reported | Reported by only one study (2/133 died in vitamin B group, 0/133 died in placebo group). | ‐ | ‐ | ||
*The risk in the intervention group (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). MD: Mean difference; SMD: Standardised mean difference; CI: Confidence interval; RR: Risk ratio; OR: Odds ratio | |||||
GRADE Working Group grades of evidence High certainty: We are very confident that the true effect lies close to that of the estimate of the effect Moderate certainty: We are moderately confident in the effect estimate: The true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different Low certainty: Our confidence in the effect estimate is limited: The true effect may be substantially different from the estimate of the effect Very low certainty: We have very little confidence in the effect estimate: The true effect is likely to be substantially different from the estimate of effect |
1 Downgraded due to risk of bias. One study was at high risk of performance bias and at unclear risk of selection and detection bias.
2 Downgraded due to inconsistency. I2 = 87%.
3 Downgraded due to imprecision. 95% CI included little or no effect and small benefit of B vitamins.
4 Downgraded due to imprecision. 95% CI included small effects in either direction.
5 Downgraded due to imprecision. Result derived from one small study.
aEpisodic memory assessed with Hopkins Verbal Learning Test, word learning and the Auditory Verbal Learning Test.
bExecutive function assessed with CLOX, the Stroop test, and the Frontal Assessment Battery.
cSpeed of processing assessed with Trail‐making Test A, digit cancellation, and the Digit‐Symbol Substitution Test.
CLOX: Clock drawing executive test D‐QOL: Dementia quality of life questionnaire MCI: Mild cognitive impairment MMSE: Mini‐mental state examination