Summary of findings for the main comparison. Vitamin C supplementation versus placebo for primary prevention of cardiovascular disease.
| Vitamin C supplementation versus placebo for primary prevention of cardiovascular disease | ||||||
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Patient or population: middle‐aged US male physicians
Settings: Not clear
Intervention: Vitamin C supplementation Comparision: 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 C supplementation | |||||
| Major cardiovascular event Physicians Follow‐up: mean 8 years | 86 per 1000 | 85 per 1000 (77 to 94) | HR 0.99 (0.89 to 1.10) | 14,641 (1 study) | ⊕⊕⊝⊝ low1,2 | Inconsistency was difficult to evaluate given that one trial assessed the primary outcome. Grey literature search is unlikely to introduce publication bias. See Appendix 2 for major cardiovascular event checklist |
| Cardiovascular mortality Physicians Follow‐up: mean 8 years | 35 per 1000 | 35 per 1000 (29 to 42) | HR 1.02 (0.85 to 1.22) | 14,641 (1 study) | ⊕⊝⊝⊝ very low1,2,3 | Inconsistency was difficult to evaluate given that one trial assessed the primary outcome. Grey literature search is unlikely to introduce publication bias. See Appendix 2 for major cardiovascular event checklist |
| All‐cause mortality Physicians Follow‐up: mean 8 years | 110 per 1000 | 117 per 1000 (107 to 128) | HR 1.07 (0.97 to 1.18) | 14,641 (1 study) | ⊕⊝⊝⊝ very low1,2,3 | Inconsistency was difficult to evaluate given that one trial assessed the primary outcome. Grey literature search is unlikely to introduce publication bias. See Appendix 2 for major cardiovascular event checklist |
| Total myocardial infarction (fatal and non‐fatal) Physicians Follow‐up: mean 8 years | 34 per 1000 | 36 per 1000 (30 to 42) | HR 1.04 (0.87 to 1.24) | 14,641 (1 study) | ⊕⊕⊝⊝ low1,2 | Inconsistency was difficult to evaluate given that one trial assessed the primary outcome. Grey literature search is unlikely to introduce publication bias. See Appendix 2 for major cardiovascular event checklist |
| Total stroke (fatal and non‐fatal) Physicians Follow‐up: mean 8 years | 34 per 1000 | 30 per 1000 (25 to 36) | HR 0.89 (0.74 to 1.07) | 14,641 (1 study) | ⊕⊕⊝⊝ low1,2 | Inconsistency was difficult to evaluate given that one trial assessed the primary outcome. Grey literature search is unlikely to introduce publication bias. See Appendix 2 for major cardiovascular event checklist |
| Self‐reported CABG/PTCA Participant self‐reports Follow‐up: mean 8 years | 97 per 1000 | 93 per 1000 (84 to 103) | HR 0.96 (0.86 to 1.07) | 14,641 (1 study) | ⊕⊕⊝⊝ low1,2 | Inconsistency was difficult to evaluate given that one trial assessed the primary outcome. Self‐reported outcomes are unlikely to introduce bias in this trial. Grey literature search is unlikely to introduce publication bias. See Appendix 2 for major cardiovascular event checklist |
| Self‐reported angina Participant self‐reports Follow‐up: mean 8 years | 105 per 1000 | 98 per 1000 (89 to 108) | HR 0.93 (0.84 to 1.03) | 14,641 (1 study) | ⊕⊕⊝⊝ low1,2 | Inconsistency was difficult to evaluate given that one trial assessed the primary outcome. Self‐reported outcomes are unlikely to introduce bias in this trial. Grey literature search is unlikely to introduce publication bias. See Appendix 2 for major cardiovascular event checklist |
| *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). CI: Confidence interval; HR: Hazard ratio; CABG: coronary artery bypass grafting; PTCA: percutaneous transluminal coronary angioplasty | ||||||
| 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. | ||||||
1 Middle‐aged US male physicians and is therefore not highly applicable to the decision context (downgraded by one for indirectness). 2 Small number of included studies (n = 1) for these outcomes (downgraded by one for imprecision). 3 8 years follow‐up (timeframe) may not be sufficient to detect mortality (downgraded by one for indirectness).