Summary of findings for the main comparison. Omega‐3 PUFA supplements compared to placebo for people with mild to moderate Alzheimer's disease.
| Omega‐3 PUFA supplements compared to placebo for people with mild to moderate Alzheimer's disease | ||||||
| Patient or population: people with mild to moderate Alzheimer's disease Setting: any setting Intervention: omega‐3 PUFA supplements Comparison: placebo | ||||||
| Outcomes | Anticipated absolute effects* (95% CI) | Relative effect (95% CI) | No of participants (studies) | Quality of the evidence (GRADE) | Comments | |
| Risk with placebo for mild to moderate Alzheimer's disease | Risk with omega‐3 PUFAs for mild to moderate Alzheimer's disease | |||||
| Any adverse event (combined: diarrhoea, urinary tract infection, falls, dizziness, agitations) Assessed with: unclear Follow‐up: mean 18 months | Study population | RR 1.02 (0.95 to 1.10) | 402 (1 RCT) | ⊕⊕⊕⊝ Moderate 1 | ‐ | |
| 878 per 1000 | 896 per 1000 (834 to 966) | |||||
| Moderate | ||||||
| 878 per 1000 | 896 per 1000 (834 to 966) | |||||
| Serious adverse events "Defined as events that result in death, hospitalization, prolongation of hospitalization, or are life threatening (based on the judgment of the study physician)" (Quinn 2010) | Study population | RR 1.05 (0.78 to 1.41) | 402 (1 RCT) | ⊕⊕⊕⊕ High | ‐ | |
| 305 per 1000 | 320 per 1000 (238 to 430) | |||||
| QoL Assessed with: QoL‐AD scale rated by participant Scale from 13 to 52 (higher = better) Follow‐up: mean 18 months |
The mean QoL was 40.02 scale points | The mean difference in QoL in the intervention group was 0.39 scale points fewer (1.79 fewer to 1.01 more) | ‐ | 269 (1 RCT) | ⊕⊕⊕⊝ Moderate 2 | ‐ |
| QoL Assessed with: QoL‐AD scale rated by participant Scale from 13 to 52 (higher = better) Follow‐up: mean 6 months | The mean QoL was 39.86 scale points | The mean difference in QoL in the intervention group was 0.1 scale points fewer (1.28 fewer to 1.08 more) | ‐ | 332 (1 RCT) | ⊕⊕⊕⊕ High | ‐ |
| Mental health (depression) Assessed with: MADRS Scale from 0 to 30 (lower = better) Follow‐up: mean 6 months | The mean depression (MADRS) score was 1.6 scale points | The mean difference in depression (MADRS) score in the intervention group was 0.1 scale points fewer (0.74 fewer to 0.54 more) | ‐ | 178 (1 RCT) | ⊕⊕⊕⊕ HIGH | ‐ |
| Mental health Assessed with: NPI Follow‐up: mean 6 months |
The mean difference in mental health (NPI) score in the intervention group was 0.1 standard deviations more (0.07 fewer to 0.27 more) 7 | ‐ | 543 (2 RCTs) | ⊕⊕⊕⊕ High | ‐ | |
| Global cognitive function Assessed with: ADAS‐Cog (different versions) Follow‐up: mean 6 months | The mean difference in global cognitive function (ADAS‐Cog) in the intervention group was 0.02 standard deviations fewer (0.19 fewer to 0.15 more) 4 | ‐ | 566 (3 RCTs) | ⊕⊕⊕⊕ High | ‐ | |
| Global cognitive function assessed with: MMSE scale Scale from 0 to 30 (higher = better) Follow‐up: mean 6 months | The mean global cognitive function ranged from 20.4 to 22.4 scale points | The mean difference in global cognitive function (MMSE) in the intervention group was 0.18 scale points more (1.05 fewer to 1.41 more) | ‐ | 202 (2 RCTs) | ⊕⊕⊕⊕ High | ‐ |
| IADL Assessed with: OARS‐IADL Scale from 0 to 14 (lower = better) Follow‐up: mean 12 months | The mean change in score for IADL was 4.2 scale points | The mean difference in the change in score for IADL in the intervention group was 3.5 scale points lower (4.3 lower to 2.7 lower) | ‐ | 22 (1 RCT) | ⊕⊕⊕⊝ Moderate 3 | ‐ |
| ADL Assessed with: DAD and ADCS‐ADL Follow‐up: mean 6 months | The mean difference in ADL in the intervention group was 0.02 standard deviations fewer (0.19 fewer to 0.16 more)5 | ‐ | 544 (2 RCTs) | ⊕⊕⊕⊕ High | ‐ | |
| Overall dementia severity (cognition and function combined) Assessed with: CDR‐SOB Scale from 0 to 18 (lower = better) Follow‐up: mean 6 months | The mean overall dementia severity (CDR‐SOB score) ranged from 6.5 to 6.75 scale points | The mean difference in overall dementia severity (CDR‐SOB score) in the intervention group was 0 scale points (0.58 fewer to 0.57 more) | ‐ | 542 (2 RCTs) | ⊕⊕⊕⊕ High | ‐ |
| Memory ‐ not measured | See comment | See comment | Not estimable | ‐ | ‐ | Outcome was not measured |
| *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). ADAS‐Cog: Alzheimer's Disease Assessment Scale ‐ Cognitive subscale; ADCS‐ADL: Alzheimer's Disease Cooperative Study ‐ Activities of Daily Living; ADL: activities of daily living; CDR‐SOB: Clinical Dementia Rating ‐ Sum of Boxes; CI: confidence interval; DAD: Disability Assessment for Dementia; IADL: instrumental activities of daily living; NPI: Neuropsychiatric Inventory; MADRS: Montgomery‐Åsberg Depression Rating Scale; MMSE: Mini‐Mental State Examination; OARS‐IADL: Older Americans Resources and Services ‐ Instrumental Activities of Daily Living; OR: odds ratio; PUFA: polyunsaturated fatty acid; QoL: quality of life; QoL‐AD: Quality of Life Alzheimer's Disease; RCT: randomised controlled trial; RR: risk ratio; SMD: standardised mean difference. | ||||||
| GRADE Working Group grades of evidence High quality: We are very confident that the true effect lies close to that of the estimate of the effect Moderate quality: 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 quality: Our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect Very low quality: 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 one level due to serious risk of bias: combined outcome (i.e. diarrhoea, falls, agitation) that includes outcomes of unclear measurement methods (i.e. dizziness).
2 Downgraded one level due to serious risk of bias: follow‐up differed between groups: 63.0% (omega‐3 PUFAs) and 72.6% (placebo).
3 Downgraded one level due to serious imprecision: wide CI; only 22 participants overall.
4 SMD presented in place of absolute values in the intervention and comparison groups as studies used the different scale versions.
5 SMD presented in place of absolute values in the interventions and comparison groups as studies used different scales to measure the same construct.