Asthma Tests Found Most Accurate at Dawn with Seasonal Variations, Reveals Study - Video

Cambridge researchers have found out that a lung function test used to help diagnose asthma works better in the morning, becoming less reliable throughout the day.

Using real world data from 1,600 patients, available through a database created for speeding up research and innovation, the team also found that its reliability differs significantly in winter compared to autumn.

Asthma is a common lung condition that can cause wheezing and shortness of breath, occasionally severe. Around 6.5% of people over six years old in the UK are affected by the condition. Treatments include the use of inhalers or nebulisers to carry medication into the lungs.

The majority of asthma attacks occur at nighttime or early in the morning. Although this may in part be due to cooler nighttime air and exposure to dust mites and allergens, it also suggests that circadian rhythms – our ‘body clocks’ – likely play a role.

In findings published in Thorax, the researchers found that starting at 8.30 am, with every hour that passed during the working day, the chances of a positive response to the test – in other words, the patient’s lungs responding to treatment, suggesting that they could have asthma – decreased by 8%.

The researchers also discovered that individuals were 33% less likely to have a positive result if tested during autumn when compared to those tested during winter.

Dr Akhilesh Jha, a Medical Research Council Clinician Scientist at the University of Cambridge and Honorary Consultant in Respiratory Medicine at CUH, said that there may be a combination of factors behind this difference.

“Our bodies have natural rhythms – our body clocks,” Jha said. “Throughout the day, the levels of different hormones in our bodies go up and down and our immune systems perform differently, for example. Any of these factors might affect how people respond to the lung function test.

Ref: Knox-Brown, B et al. The effect of time of day and seasonal variation on bronchodilator responsiveness: The SPIRO-TIMETRY study. Thorax; 12 March 2025; DOI: 10.1136/thorax-2024-222773