Shift work takes place on a schedule outside the traditional 9 am – 5 pm day and can involve evening or night shifts, early morning shifts, and rotating shifts. Around 20 per cent of the UK workforce is now engaged in shift working.

An international team of scientists led by The University of Manchester and Manchester University NHS Foundation Trust has compared the effect of day working with shift working on asthma diagnosis, lung function and symptoms. The team found that shift workers, especially those working permanent night shifts, showed increased risks of asthma, especially moderate or severe asthma.

The study of 280,000 participants  gathered medical, lifestyle and employment information and asked workers if they were a morning or evening person. Natural early risers ('larks'), had a 55 per cent higher risk of moderate to severe asthma if they worked irregular shifts, including nights. Wheezing or airway whistling  - an indication of breathing difficulties - was 11 to 18 per cent higher for permanent night shift workers,

Lead author Dr Hannah Durrington said, "The results highlight the need to improve guidelines or develop laws for employers to protect shift workers."

The study is published in Thorax, journal of the British Thoracic Society.