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Fish oil linked to lower Alzheimer’s risk


3 Star

Fish oil linked to lower Alzheimer’s risk

Our Review Summary

This story reported on the findings from a recent research study that found lower rates of dementia in individuals who had higher levels of docosahexaenoic acid (DHA) in their blood.  They were also able to show individuals who consumed 2 or more servings of fish per week were found to have higher levels of DHA.

The reporting about this study is a good example of where the relative risk reduction sounds impressive but the absolute risk reduction is small.  Yet the story provided only the relative risk numbers, not the absolute.  (Read more about absolute vs. relative risk.)

Although it's good that the story pointed out the harms that are associated with fish oil consumption and the lack of FDA approval of fish oil as a means to prevent dementia, it neglected to mention that there currently are no evidence-based means to reduce the incidence of dementia.  The story also ought to have included information about other reasons the authors might have found the results they did (chance, confouding dietary or behavioral patterns, etc). Because it is possible that these and not the fish consumption per se are associated with reduced dementia, it is information that a reader should be aware of. 

The headline of the story – "Fish Oil Linked to Lower Alzheimer's Risk" – is somewhat misleading because the results of the story demonstrated that fish oil was associated with lower risk of all-cause dementia; when an attempt was made to parse out the effect of fish oil on Alzheimer's disease specifically, its effect was not statistically significant.  It should be noted that this story was not the only one to fail to appreciate this distinction. The editorial accompanying this research in the Archives of Neurology was entitled "Docosahexaenoic Acid and Alzheimer Disease" and nowhere in the editorial was the distinction made between Alzheimer's and all-cause dementia. 



Does the story adequately discuss the costs of the intervention?

Not Satisfactory

This story did not include any cost estimates for fish or docosaheaenoic acid (DHA) containing supplements.  It also did not include an estimate for the amount of supplements that would be needed to result in the plasma levels of DHA seen to be associated with lower dementia risk.

Does the story adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

Early in the story, it mentioned that the research involved 899 people and that 99 people developed dementia during the course of the study.  This works out to a total incidence of dementia of 11%, something that was not explicitly stated in the story.  The piece then went on to discuss that  that two or more servings of fish a week reduced the risk of dementia by 39%.  This is a relative risk reduction.  Before readers can put that in context, they would really need to have the absolute risk of developing dementia.   (Read more about absolute vs. relative risk.)

While it is true that the original source piece for this story did not contain this information, the story could have raised the question.

Does the story adequately explain/quantify the harms of the intervention?


The story mentioned potential harms from fish oil consumption and included speculation on potential harms from fish consumption.

Does the story seem to grasp the quality of the evidence?

Not Satisfactory

This story reported on the observations reported in one recently published paper which found that there appeared to be a lower risk of developing demnetia for individuals with the highest level of plasma levels of docosaheaenoic acid (DHA).  It mentioned that the study reported on has been published in the Archives of Neurology, that the data were part of the Framingham Heart Study and that the individuals were followed for an average of 9 years.

It would have been useful to more clearly describe for readers the design of the prospective study giving rise to the results reported on. A blood sample was taken from people who did not have dementia, a diet history was collected from about half of the people, then they were follwed for an average of 9 years to determine the incidence of dementia that was observed.   There did not appear to be a dose response in terms of the protective effect of DHA, but rather a reduced risk for developing dementia was seen only in those with the highest DHA levels. Plasma DHA levels were seen to correlate with the number of servings of fish or the amount of DHA consumed.

The story also could have described other potential confounders that may have contributed to the results.  There are other behaviors that are associated with reduced dementia that may be more common in those who eat more fish (social activities, better dietary variety, or others).

Does the story commit disease-mongering?


This story did not appear to disease monger. 

Does the story use independent sources and identify conflicts of interest?


This story was based on information from an original research study and included quotes from the study senior author as well as material from an editorial about the research study.

Does the story compare the new approach with existing alternatives?

Not Satisfactory

This story did not mention the lack of evidence-based measures to prevent Alzheimer disease.  A brief statement about lack of strong evidence would help guide readers in this regard.

Does the story establish the availability of the treatment/test/product/procedure?


This story mentioned that omega-3 fatty acid docosaheaenoic acid (DHA) was found in fatty fish, as well as supplements in the form of fish oil or DHA.  It was good to point out that neither DHA or fish oild supplements have FDA approval for prevention of dementia.

The story curiously mentioned that it was also found in some meats. However, the only tissues in which DHA is found in significant quantities are the brain, retina, and testes – which are not frequently consumed by people.  Thus the story ought not to have included 'some meats' as a source of DHA.

Does the story establish the true novelty of the approach?


The story reported that the results of the current study were consistent with earlier data.

Does the story appear to rely solely or largely on a news release?


Does not appear to rely on a press release.

Total Score: 6 of 10 Satisfactory


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