Asthma is often aggravated during the night-time hours. Underlying reasons can be multifactorial, including environmental and behavioural triggers (air temperature, humidity, dust, sleeping position, etc.). However, acquired knowledge of circadian rhythm and its intrinsic role in biological control suggest there are probably mechanisms driving the night-time emergence of symptoms that remain to be identified.

Scheer et al. set out to determine how (if at all) the circadian system contributes to nocturnal asthma. Employing protocols to distinguish circadian effects from those identified as environmental or behavioural, they disrupted the circadian cycles in 17 asthmatic individuals. They found that night-time asthma is often unnoticed, with the symptomatic individual sleeping through periodic nocturnal asthma. They also observed bronchodilator use was four times higher during the night-time and in those individuals with the lowest pulmonary function. These subjects exhibited the largest variations in circadian effects on their asthma.

The most significant finding in this study was that the circadian system has a major role in nocturnal asthma, adding further weight to the case for chronotherapy as a key strategy in asthma management.

Read the full article in Proceedings of the National Academy of Sciences of the USA 118 e2018486118