DO IT 2010.
| Methods | Diet and Omega 3 Intervention Trial on Atherosclerosis (DO IT) Randomisation: RCT, parallel, 2 × 2 factorial, (n‐3 DHA + EPA vs n‐6 LA also dietary advice intervention), 36 months Summary risk of bias: moderate or high |
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| Participants | Elderly men with longstanding dyslipidaemia or hypertension (a subset of Oslo Diet heart study) N: intervention 282 (140 n‐3 capsules + 142 n‐3 capsules and dietary advice), control 281 (142 placebo capsules + 139 placebo capsules and dietary advice) Level of risk for CVD: moderate Men: intervention 100%, control 100% Mean age in years (SD): intervention 70.4 (2.9), control 69.7 (3.0) years Age range: 64‐76 years Smokers: intervention 35%, control 33% Hypertension: intervention 29%, control 27% Medications taken by at least 50% of those in the control group: none Medications taken by 20%‐49% of those in the control group: statins and acetylsalicylic acid Medications taken by some, but less than 20% of the control group: β‐blockers, ACE inhibitors and nitrates Location: Norway Ethnicity: not reported |
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| Interventions | Type: supplement/ capsule (also dietary advice as the factorial intervention) Comparison: EPA + DHA vs omega‐6 Intervention: 2 × 2 capsules/d incl 2.4 g/d of omega‐3 PUFA (Pikasol, 0.84 g/d EPA plus 0.48 g/d DHA plus 8.4 mg/d tocopherols). Dose: 1.32 g/d EPA + DHA Control: 2 × 2 capsules/d inc 4 g/d corn oil (2.24 g/d linoleic, 1.28 g/d oleic acid, 16 mg/d tocopherols) Compliance: pharmacy records suggested that > 90% of supplements were taken, and plasma EPA and DHA were raised in intervention compared to control participants. Duration of intervention: 36 months |
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| Outcomes | Main study outcome: atherosclerosis progression. Dropouts: intervention 14 died, 20 others discontinued, control 24 died, 18 others discontinued Available outcomes: mortality, cardiovascular deaths, CHD events, CV events, MI, stroke, diabetes, glucose, lipids, cancer diagnosis, cancer deaths, sudden death, BMI (waist circumference reported as median, IQR) Response to contact: yes (data provided) |
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| Notes | The other 2 × 2 intervention was dietary counselling to increase both omega‐3 and omega‐6 fats as well as fruit and vegetables. Study funding: Norwegian Cardiovascular Council, Norwegian retail company RIMI, vegetable oil and margarine supplied by the Norwegian food company Mills DA and placebo capsules by LUBE |
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| Risk of bias | ||
| Bias | Authors' judgement | Support for judgement |
| Random sequence generation (selection bias) | Low risk | Permuted block randomisation, no clear mechanism provided |
| Allocation concealment (selection bias) | Unclear risk | No details provided |
| Blinding of participants and personnel (performance bias) All outcomes | Unclear risk | Capsules of fish oil or placebo taken, but unclear whether blinded and if so, how well or successfully |
| Blinding of outcome assessment (detection bias) All outcomes | Low risk | "Mortality data were supplied from the Norwegian Cause of Death Registry, and all clinical events were confirmed by hospital records and verified by an independent cardiologist" |
| Incomplete outcome data (attrition bias) All outcomes | Low risk | No attrition as deaths and events collected from centralised register |
| Selective reporting (reporting bias) | Unclear risk | Trials registry entry submitted after the outcomes papers were published. |
| Attention | Low risk | No suggestion of attention bias between verum and placebo supplement arms |
| Compliance | Low risk | Pharmacy records suggested that > 90% of supplements were taken, and plasma EPA and DHA were raised in intervention compared to control participants |
| Other bias | Low risk | None noted |