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Pooled review (meta-analysis)

Pooled review of 79 trials: no clear effect of fish oil on heart events

Abdelhamid and colleagues · The Cochrane database of systematic reviews · 2018

Original title: Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease.

Under review. A person has not yet checked this summary against the paper. It is written from the PubMed abstract. Until a person checks it, search engines are asked not to list this page.

What the study found

No difference

Little or no effect on all-cause death (RR 0.98, 95% CI 0.90 to 1.03), heart events (RR 0.99, 95% CI 0.94 to 1.04), stroke (RR 1.06) or arrhythmia (RR 0.97). The small drop in heart-disease events (RR 0.93) did not hold in sensitivity analyses.

The study at a glance

Type of study
Pooled review (meta-analysis)
Who or what was studied
79 studies, 112,059 people · adults at varying heart risk, in 79 trials lasting 12 to 72 months
What was tested
Fish-oil omega-3 (EPA and DHA) supplements or advice, versus placebo or usual intake
What it measured
The question itself: heart attacks, strokes and heart deaths
Who has a stake
No stake declared
All authors: none known. Funded by the UK Medical Research Council.
Journal
The Cochrane database of systematic reviews, 2018
Source
PubMed record 30019766. This page is based on the abstract only.

How much this study counts

  • ✓Pools the results of 79 studies with 112,059 people.
  • •A pooled review is only as strong as the studies it pools.
  • ✓Measured the question itself: heart attacks, strokes and heart deaths.
  • ✓No competing interests declared.
  • •Summarized from the PubMed abstract only. The full paper may hold details the abstract leaves out.

✓ Strength– Limit• Note

These points come from fixed rules about the type of study, its size and length, what it measured, and who has a stake. Every study on Digestery gets the same rules.

Where this study sits

This paper is not on the ladder. It is a pooled review (meta-analysis), and reviews and opinion pieces discuss studies that are already counted on the steps below.

↑ Stronger evidence

  1. Trials in people: heart attacks, strokes and heart deaths

    11

    7 benefit, 4 no difference

  2. Trials in people: other measures

    3

    1 benefit, 2 no difference

  3. Trials in people: lab tests or safety

    0

    None among the papers we read.

  4. Population studies

    0

    None among the papers we read.

  5. Blood levels and genes

    0

    None among the papers we read.

↓ Weaker evidence

  • Points to benefit
  • Mixed
  • No difference
  • No direction
  • Points to harm

How it fits with the other research

The short answer to “Does fish oil prevent heart disease?”

Little or no effect in most trials.

Confidence: moderate. Based on 21 on-topic papers.

Read the full answer
  • Part of the finding “Big reviews find little or no overall effect”.
  • Summed up in “What reviews found”: The 2018 version pooled 79 trials with 112,059 people. It found little or no effect on deaths or heart events, and said earlier signs of benefit came from trials with higher risk of bias.

Other reviews on this question

See all 21 studies on this question

How this page was made

Label

First read of the abstract
Claude Sonnet
Independent second read
Claude Haiku
Differences settled
The two reads agreed on every checked field. Claude Opus 5.5.
Headline
Claude Sonnet, from the checked study record. A script checked its numbers and wording.
Numbers
Checked against the abstract by a script
“How much this study counts”
Fixed rules, the same for every study
Source check by a person
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