Summary of findings for the main comparison. Vitamin E (capsules 2000 IU/day in two divided doses) compared to placebo for people with Alzheimer's disease.
| Vitamin E (capsules 2000 IU/day in 2 divided doses) compared to placebo for people with Alzheimer's disease | ||||||
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Patient or population: people with Alzheimer's disease Settings: multicentre, US Intervention: vitamin E (capsules 2000 IU/day in 2 divided doses) Comparison: placebo | ||||||
| Outcomes | Illustrative comparative risks* (95% CI) | Relative effect (95% CI) | No of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Assumed risk | Corresponding risk | |||||
| Placebo | Vitamin E (capsules 2000 IU/day in 2 divided doses) | |||||
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Cognitive function
LS mean change from baseline using the ADAS‐Cog Scale from: 0 to 70 Follow‐up: 6 to 48 months |
The LS mean change from baseline in cognitive function in placebo group was 7.78 | The LS mean change from baseline in cognitive function in the intervention group was 1.81 lower (3.75 lower to 0.13 higher) | ‐ | 272 (1 study) | ⊕⊕⊕⊝ Moderate1 | Higher scores represent worse cognitive function. A 4‐point difference in ADAS‐cog has been considered the MCID. |
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Adverse events Number of participants reporting ≥ 1 serious adverse event Follow‐up: 6 to 48 months |
625 per 1000 | 538 per 1000 (444 to 656) | RR 0.86 (0.71 to 1.05) | 304 (1 study) | ⊕⊕⊕⊝ Moderate1 | ‐ |
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Deaths Number of deaths Follow‐up: 6 to 48 months |
204 per 1000 | 171 per 1000 (106 to 273) | RR 0.84 (0.52 to 1.34) | 304 (1 study) | ⊕⊕⊕⊝ Moderate1 | ‐ |
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Activities of daily living
LS mean change from baseline using the ADCS‐ADL Scale from: 0 to 78 Follow‐up: 6 to 48 months |
The LS mean change from baseline in activities of daily living in the placebo group was ‐16.96 | The LS mean change from baseline in activities of daily living in the intervention group was 3.15 higher (0.07 to 6.23 higher) | ‐ | 280 (1 study) | ⊕⊕⊕⊝ Moderate1 | Higher scores represent better activities of daily living. |
| *The basis for the assumed risk (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (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). ADAS‐Cog: Alzheimer Disease Assessment Scale ‐ Cognitive Subscale; ADCS‐ADL: Alzheimer's Disease Cooperative Study/Activities of Daily Living Inventory;CI: confidence interval; LS: least square; MCID: minimum clinically important difference; RR: risk ratio. | ||||||
| GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate. | ||||||
1Quality downgraded one level due to imprecision. Evidence from a single study of modest size. This is supported by dichotomous data not reaching the optimal information size criterion (assuming α of 0.05, and β of 0.2) (Guyatt 2011).