Summary of findings 2. Beta‐carotene versus placebo.
| Beta‐carotene versus placebo | ||||||
| Patient or population: general population Setting: community Intervention: beta‐carotene* Comparison: placebo | ||||||
| Outcomes | Anticipated absolute effects (95% CI) | Relative effect (95% CI) | № of participants (studies) | Certainty of the evidence (GRADE) | Comments | |
| Risk with placebo** | Risk with beta‐carotene | |||||
| Any AMD | 150 per 1000 | 150 per 1000 (132 to 171) | RR 1.00 (0.88 to 1.14) | 22,083 (2 RCTs) | ⊕⊕⊕⊕ HIGH | Average duration of treatment and follow‐up was 6 years in one study and 12 years in the other study |
| Late AMD (either neovascular AMD or geographic atrophy or both) | 5 per 1000 | 5 per 1000 (3 to 6) | RR 0.90 (0.65 to 1.24) | 22,083 (2 RCTs) | ⊕⊕⊕⊝ MODERATE 1 | Average duration of treatment and follow‐up was 6 years in one study and 12 years in the other study |
| Neovascular AMD | 3 per 1000 | 2 per 1000 (1 to 6) | RR 0.61 (0.17 to 2.15) | 941 (1 RCT) | ⊕⊝⊝⊝ VERY LOW 2 | Average duration of treatment and follow‐up was 6 years |
| Geographic atrophy | 2 per 1000 | 1 per 1000 (0 to 6) | RR 0.31 (0.03 to 2.93) | 941 (1 RCT) | ⊕⊝⊝⊝ VERY LOW 2 | Average duration of treatment and follow‐up was 6 years |
| Quality of life | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| Adverse effects | ‐ | ‐ | ‐ | ⊕⊕⊕⊕ HIGH | Beta‐carotene associated with increased risk of lung cancer in people who smoke. | |
| Resource use and costs | ‐ | ‐ | ‐ | ‐ | ‐ | Not reported |
| * Dose of beta‐carotene used was 20 mg/day in one study and 50 mg/alternate days in the other study. **The risk in the placebo group is the median risk in the control groups of the four included studies in Table 1. 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 | ||||||
| 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 one level for imprecision due to wide confidence intervals i.e. are below 0.8 or above 1.25.
2 Downgraded one level for indirectness (only one trial in male smokers) and downgraded two levels for imprecision as very few cases (10 neovascular AMD, 4 geographic atrophy)