Studies have shown that the clock protein REV-ERBα controls airway hyperresponsiveness at different times of day, and that knocking down the Rev-erbα gene abolishes the time-of-day effect.6 7 The results from our study are consistent with the recently published RADicA study, which in a relatively small sample of patients with suspected asthma found that patients self-reported their worst symptoms in the morning and night, and that patients were more likely to demonstrate bronchodilator responsiveness in the morning compared with the afternoon.8 Here, NR1D1 is linked to asthma.