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Release suggests seafood diet helps slow cognitive decline – but didn’t include study limitations

Stave off cognitive decline with seafood

Our Review Summary

fishThe news release is a recap of a recent journal article published in the journal Neurology, and reports that older adults who eat seafood at least once per week saw slower declines in two specific cognitive areas (semantic memory and perceptual speed) than older adults who eat less than one serving of seafood per week. The release provides a good measured overview of the study but does not quantify the benefits or address the limitations of the study.

 

Why This Matters

Most people plan on aging; it happens whether we like it or not. And many people have experiences with loved ones whose cognitive abilities — such as memory — have declined with age. In short, issues regarding cognitive decline associated with aging are relevant to almost everyone. Research that offers simple steps that could slow memory loss are, therefore, of widespread interest. For the same reason, it’s important to approach these simple solutions with caution. How much does it slow loss, for example? That’s not clear from the release, and yet it’s likely the most pertinent question for many readers.

Criteria

Does the news release adequately discuss the costs of the intervention?

Not Applicable

Cost isn’t discussed. And because it’s about a widely-consumed food that is a staple for many diets, we’ll rate it not applicable. However, it’s worth noting that seafood can be more expensive than many other types of food. What’s more, since the story discusses seafood primarily as a vehicle for omega-3 fatty acids, cost becomes even more of an issue. And when it comes to omega-3 fatty acids, not all seafood is created equal. Salmon, for example, has a lot more omega-3 fatty acids than a similar serving size of catfish — but it’s also a lot more expensive. There is also the issue of accessibility. People living in so-called “food deserts,” which are often found in socioeconomically challenged areas, may have difficulty even reaching stores or restaurants that sell seafood.

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

Not Satisfactory

Benefits are discussed using only vague language. For example: “age-related memory loss and thinking problems of participants in the study who reported eating seafood less than once a week declined more rapidly compared to those who ate at least one seafood meal per week.” How much more rapidly? Or: “People who ate more seafood had reduced rates of decline in the semantic memory, which is memory of verbal information. They also had slower rates of decline in a test of perceptual speed, or the ability to quickly compare letters, objects and patterns.” But how much less decline was there of semantic memory? And how much slower was the decline in regard to perceptual speed? The release doesn’t tell us.

It would have been helpful for the news release to present the raw numbers relating to cognitive decline in each group and to provide some context to help readers understand their significance (such as “performance on the semantic memory test dropped by X amount in this group and Y in the other group,” for example).

Does the news release adequately explain/quantify the harms of the intervention?

Not Applicable

The study population in this specific study was made up of older adults (mean age of 81.4 years old). There are few, if any, risks associated with eating one seafood meal per week for older adults. However, the release might have warned that both the FDA and the EPA, while encouraging pregnant and breastfeeding women to consume two to three servings of fish weekly, now recommend that they choose fish that is low in mercury (which include salmon, shrimp, pollock, tuna (light canned), tilapia, catfish, and cod).

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

The news release does a good job of explaining the size and design of the study. However, it doesn’t point out that the study is observational which means it doesn’t show there is a cause and effect between seafood consumption and cognitive decline. In some instances the release uses active verbs: “may protect,” “may slow” which imply causality that isn’t proven in observational studies.

The release would also have been stronger if it had addressed the study’s limitations. For example, data on the diet of study participants was collected via an annual questionnaire completed by study participants. This presents two challenges. First, it relies on the memory of the study participants, which introduces significant room for reporting errors. Second, the questionnaire categories are extremely broad (e.g., “fish sticks, fish cakes and fish sandwiches” and “fresh fish as a main dish”). These broad categories are problematic because eating a salmon filet and eating a serving of popcorn shrimp are given the same weight, even though they are nutritionally dissimilar. Also, while the release tells readers the number of study participants (951), it doesn’t offer readers any insight into whether that’s a big number or a small one. As the Neurology paper itself notes: “Another limitation of the study is the relatively small sample size to detect modest associations within subgroups.”

Does the news release commit disease-mongering?

Satisfactory

The opening paragraph talks about protecting against “thinking problems.” Readers could be excused if they translate “thinking problems” to mean senility or dementia. But the story quickly notes that “cognitive abilities naturally decline as part of the normal aging process” — and that’s what we wanted to see. This study was about slowing that normal decline, not addressing specific medical conditions such as Alzheimer’s disease.

Does the news release identify funding sources & disclose conflicts of interest?

Satisfactory

The story clearly and prominently lists the sources of funding for the work, and there are no apparent conflicts of interest.

Does the news release compare the new approach with existing alternatives?

Satisfactory

The story says that “researchers adjusted for other factors that could affect memory and thinking skills, such as education, physical activity, smoking and participating in mentally stimulating activities.” It doesn’t tell us which are potentially good (and which are bad), but it’s sufficient for a Satisfactory rating.

The release would have been stronger if it had addressed the question (probably on some on readers’ minds) about whether fatty acid supplements could possibly have the same effect that the researchers observed with seafood consumption. These supplements are widely used, not to mention costly, so this may have been worth including.

Does the news release establish the availability of the treatment/test/product/procedure?

Not Applicable

People have been eating fish for rather a long time, so we’ll rate this Not Applicable.

Does the news release establish the true novelty of the approach?

Satisfactory

The story states that: “While epidemiologic studies have shown the importance of seafood and omega-3 fatty acids in preventing dementia, few prior studies have examined their associations with specific types of cognitive ability.” That gets it a satisfactory rating. However, it’s worth noting that the story does not get to the novel aspect of the findings — the “associations with specific types of cognitive ability” — until the sixth paragraph. If that’s what’s new in the news, one wonders why it wasn’t addressed higher.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?

Satisfactory

This is a close one, but mainly because of the headline. Declines in semantic memory and perceptual speed weren’t prevented, or even postponed, they were simply slowed down. That said, we’ll give the release the benefit of the doubt. The body of the release used language that was measured and appropriate.

Total Score: 5 of 7 Satisfactory

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