Painkiller link to childhood asthma unlikely to be causal, researchers say

A previously reported association between analgesic use in pregnancy and childhood asthma is likely to result from confounding factors, researchers have concluded (17 March 2019)^[1]
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The research, published in the European Respiratory Journal, used data from a Swedish health registry on 492,999 children born between July 2005 and December 2010. Data on maternal prescribed analgesic use were obtained from the national drug register.

After adjustment for confounding factors, the risk of childhood asthma/wheeze at four years of age was elevated by 39% for offspring whose mothers were prescribed opioids, 19% for antimigraine drugs and 47% for paracetamol.

The team said that, given that there was an increased risk for different analgesics with different modes of action, it was unlikely that the observed associations were causal. They suggested that the findings were more likely to be confounded by maternal factors linked to use of these drugs, such as chronic pain or anxiety.

“There have been previous calls for placebo-controlled trials to definitively test the paracetamol-asthma hypothesis,” the team wrote.

“We would argue, on the basis of our latest findings, that the case for a trial in pregnancy, which would present considerable practical and ethical challenges, is now less strong.”