To the Editor Dr Litonjua and colleagues reported the results of a randomized clinical trial investigating the effect of prenatal supplementation with vitamin D on asthma and wheezing in young offspring.1 The study provides an example of the problems with so-called “statistical significance” and the interpretation of P values with reference to an arbitrary threshold. The authors estimated that high-dose vitamin D given in pregnancy was associated with a reduced risk of the coprimary outcome of recurrent wheeze (hazard ratio [HR], 0.8 [95% CI, 0.6-1.0]), with an associated P value of .051.
Bhaskaran K, Smeeth L, Evans S. Prenatal Vitamin D and Offspring Wheezing. JAMA. 2016;315(24):2730. doi:10.1001/jama.2016.4108