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The study by Shaheen et al 1 rightly pointed out that some patients with asthma deliberately avoid aspirin and are more likely to use paracetamol, hence a “consumer selection bias”. However, they failed to mention the “professional's selection bias”. Any standard textbooks or prescribing references state that aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) could potentially worsen asthma.2 Health professionals will therefore certainly choose paracetamol for patients with asthma to avoid potential adverse reactions to NSAIDs and litigation problems.3
It is unlikely that this bias could be resolved by a pharmacoepidemiological study. Recent reports in the general press and television about the study could convey the wrong impression to patients with asthma which could direct them to self-select aspirin or ibuprofen. Fatal or near fatal cases associated with aspirin and NSAIDs have been reported.4 ,5 Finally, I agree with Shaheenet al that further studies are required.
We were interested to read of the association between paracetamol use and asthma in adults reported by Shaheenet al.1-1 We recognise that the link is not causal and that further randomised trials are needed to clarify this link.
In their paper they comment that they have controlled for potentially confounding factors. We were concerned that one of their definitions for “asthmatic” was the positive answer to the question “Have you been woken by an attack of shortness of breath over the last 12 months?”. The association they have shown was with people who use paracetamol weekly or daily. We do not believe that there has been an attempt to control for confounding factors, particularly anxiety leading to headaches and symptoms of breathlessness and hyperventilation. We would encourage researchers taking this matter further to consider this in their study designs.
References
- 1-1.↵
Shaheen et al have stated that there …