Summary of findings 2. Vitamin E compared to placebo for MCI.
| Vitamin E compared to placebo for MCI | |||
| Patient or population: MCI Setting: community Intervention: vitamin E Comparison: placebo | |||
| Outcomes | Impact | № of participants (studies) | Certainty of the evidence (GRADE) |
| Incidence of dementia due to Alzheimer's disease follow‐up: 36 months | 76 cases in vitamin E group and 73 cases in placebo group (HR 1.02, 95% CI 0.74 to 1.41) | 516 (1 RCT) | ⊕⊕⊕⊝ MODERATE 1 |
| Overall cognitive functioning assessed with: MMSE and ADAS‐cog follow‐up: 36 months | Single study reported no significant difference between groups in changes from baseline of MMSE or ADAS‐cog. Sample sizes not reported. | (1 RCT) | ⊕⊕⊝⊝ LOW 2 3 |
| Episodic memory assessed with: z‐score incorporating various instrumentsa follow‐up: 36 months | Single study reported no significant difference between groups. Sample size not reported. | (1 RCT) | ⊕⊕⊝⊝ LOW 2 3 |
| Executive functioning assessed with: z‐score incorporating various instrumentsb follow‐up: 36 months | Single study reported no significant difference between groups. Sample size not reported. | (1 RCT) | ⊕⊕⊝⊝ LOW 2 3 |
| Quality of life ‐ not measured | ‐ | ‐ | |
| Mortality | No significant difference in deaths reported between vitamin E, donepezil, and placebo groups during double‐blind phase of trial. | (1 RCT) | ‐ |
| *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). 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 imprecision. 95% CI around hazard ratio included possible effect in both directions.
2 Downgraded due to imprecision. Single study. Sample size for this outcome not reported.
3 Downgraded due to risk of bias. High risk of bias due to incomplete outcome data and selective reporting.
aEpisodic memory assessed using standardised composite z‐score incorporating ADAS immediate and delayed word‐recall scores and the New York University immediate and delayed paragraph‐recall scores.
bExecutive function assessed using standardised composite z‐score incorporating the digits‐backward test, Symbol Digit Modalities Test, and number‐cancellation test.
ADAS‐cog: Alzheimer's Disease Assessment Scale ‐ cognitive MCI: Mild cognitive impairment MMSE: Mini‐mental state examination