This New York Times story looks at a new study showing a reduced risk of asthma in the children of mothers who took high doses of fish oil during the last trimester of pregnancy.
The story was strong–it did a lot of things well. We were especially pleased to see the Times use both absolute and relative risk numbers when conveying the measured benefit. We learn, for example, that fish oil reduced the risk of asthma 31 percent, the relative risk benefit. That is tempered by inclusion of the absolute risk reduction–16.9% of mothers who supplemented had children with asthma, compared to 23.7 of mothers taking a placebo. This helps readers keep expectations in check.
The main shortcoming is the story’s failure to disclose relevant conflicts of interest. One of the researchers has a financial interest in the genetic testing he advocates in the story — and readers should be aware of that interest as they consider his recommendations.
Other than avoidance of smoking by the mother, there is currently no known way to prevent asthma from developing in a child, and the World Health Organization defines its global health and economic impact as “severe.”
Given how common this disease is, news coverage on this study will be highly read, making it vital to distill the results accurately. This story did so, and provided important context to let parents know that researchers aren’t yet ready to recommend high-dose fish oil supplementation to pregnant women.
The story did not discuss cost. There are dozens of fish oil supplements on the market and their cost varies widely. The story could have given some sense of the financial impact that this regimen would have.
This was a strong point of the story, giving us both absolute and relative risk figures up front in the second paragraph:
Among children whose mothers took fish-oil capsules, 16.9 percent had asthma by age 3, compared with 23.7 percent whose mothers were given placebos. The difference, nearly 7 percentage points, translates to a risk reduction of about 31 percent.
Too often, even when stories do provide absolute risk figures, they highlight relative risks high up in the story and bury the absolute risk information far down in the text where it’s less likely to be read.
The story explains that no adverse events were associated with the intervention. However, the harms assessed by the researchers were things like maternal or infant death, emergency caesarean delivery, and preterm birth. They didn’t assess (and the story didn’t mention) less serious harms like fishy taste, nausea, belching, and heartburn that are commonly associated with fish oil capsules and which might make this regimen burdensome for pregnant women.
Moreover, it would have been useful if the story had also noted that the reason researchers want to replicate the results in a larger group of women is to make sure these very high doses of fish oil are indeed safe.
The story gives us details of the study–how many women were enrolled, that there was a placebo group, and that the children were followed for seven years. An independent source also explains that the study was “well designed and carefully performed.”
The story does not disease monger–childhood asthma is a common and often exasperating condition that many parents grapple with.
The story clearly explains who funded the study, and includes an independent source. But it doesn’t note the extensive conflicts of interest reported by the lead author who’s quoted in the piece:
Dr. Bisgaard reports receiving consulting fees from Chiesi Pharmaceuticals and Boehringer Ingelheim, and Drs. Bisgaard and Bønnelykke report being named on a pending patent related to the prevention of childhood asthma through FADS genotyping and the assessment of blood levels of eicosapentaenoic acid and docosahexaenoic acid in pregnant mothers.
The patent filing related to genetic testing is particularly relevant, given that the researcher advocates genetic testing and testing of fish oil levels in pregnant women to determine who might benefit most from supplementation.
Aside from avoidance of maternal smoking, there are no known ways to reduce the risk of developing asthma in childhood. The story explains this is why doctors are testing this method, and excited by the findings.
The story explains that the “capsules were an over-the-counter product called Incromega TG33/22, a fish extract made by the British chemical company Croda Health Care.”
And in regard to whether women should start taking the supplement to lower asthma risk in their babies, the story lets us know researchers “are not ready to recommend that pregnant women routinely take fish oil” due to the very high dose used in this study. Further research is needed first to establish safety and confirm benefit.
We learn that previous studies on this topic were inconclusive, and so the inference is that this is the first time more conclusive results were seen, especially regarding the benefit in women who had lower-than-normal levels of the fatty acids in their blood.
This story did not rely on the news release.