They found that the chances of a positive response — where the patient's lungs responded to treatment, suggesting they might have asthma — decreased by eight percent with every passing hour from 8.30 am.
Published Mar 29, 2025 | 7:00 AM ⚊ Updated Mar 29, 2025 | 7:00 AM
A person using an inhaler. (iStock)
Synopsis: A new study published in Thorax BMJ suggested that the accuracy of a typical asthma test depends on the time of day and even the season. It said the most accurate results can be obtained if tested in the morning.
If you’re about to get tested for asthma, consider booking a morning appointment for the most reliable results. A new study published in Thorax BMJ suggested that the accuracy of a typical asthma test depends on the time of day and even the season.
Doctors often diagnose asthma, a common lug condition that can cause wheezing and shortness of breath, using a lung function test called spirometry that measures how well your airways respond to medication.
In this test, the patient is asked to inhale and exhale deeply and quickly for as long as possible into a tube to assess lung function.
This new research, conducted by researchers at the Victor Phillip Dahdaleh Heart and Lung Research Institute in collaboration with the University of Cambridge and Royal Papworth Hospital NHS Foundation Trust, emphasises the importance of considering both the time of day and the season when performing diagnostic tests for asthma.
“For every additional hour later in the workday that the test is conducted the likelihood of getting a positive response (indicating asthma) decreases by eight percent,” the study authors said.
The researchers wanted to explore whether circadian rhythms have an impact on our ability to diagnose asthma using routinely performed clinical testing.
The study analysed data from patients over seven years, from 2016 to 2023, and included patients aged 18 or older, at the time of testing, who had acceptable and reproducible pre- and post-bronchodilator spirometry.
They found that the chances of a positive response — where the patient’s lungs responded to treatment, suggesting they might have asthma — decreased by eight percent with every passing hour from 8.30 am.
The study also found that asthma test results varied with the seasons, with winter tests being more dependable than those done in autumn.
“Morning tests are more reliable due to biological rhythms affecting lung function, and winter months show higher bronchodilator responsiveness compared to other seasons,” the authors stated.
Dr Ben Knox-Brown, Lead Research Respiratory Physiologist at RPH said in the study, “Given that we know about how the risk of an asthma attack changes between day and night, we expected to find a difference in how people responded to the lung function test. However, we were surprised by the size of the effect.
“This has potential implications. Doing the test in the morning would give a more reliable representation of a patient’s response to the medication than doing it in the afternoon, which is important when confirming a diagnosis such as asthma,”
Interestingly, this supports previous research, such as the RADicA study, which found that asthma symptoms worsen in the morning and night, making morning tests more likely to confirm asthma.
A possible explanation lies in the REV-ERBa clock protein, which regulates airway responsiveness at different times of the day. Previous studies have shown that removing this protein eliminates time-based differences in lung function, further proving that asthma symptoms follow a circadian rhythm.
“Taken together, these findings suggest that performing diagnostic testing when patients are most symptomatic, that is in the morning, may improve diagnostic testing results,” said the authors.
Also, when compared to other seasons, the bronchodilator responsiveness was higher in winter. Past studies have shown that asthma symptoms increase during the pollen season (summer) in younger patients with allergic asthma. However, in older patients — who have a higher risk of asthma-related hospitalisations and mortality — symptoms peak in winter.
This suggests that different age groups may have seasonal variations in asthma severity, which doctors should consider when diagnosing and treating patients, the said.
“We saw a slight increase in the proportion with bronchodilator responsiveness in the summer compared with the spring and autumn, but still to a lesser extent than seen in the winter,” the authors of the study said.
Asthma is a long-term condition that affects millions of people in India. Getting the right diagnosis is the first step to managing it properly. This study highlights how small changes — like timing your test right — can make a big difference in ensuring you get the right treatment.
Speaking to South First, Dr Ravindra Mehta, Founder Director of VAAYU Chest and Sleep Center and Head of Apollo Bangalore Integrated Pulmonology Services, said, “This study reinforces what we already know — that asthma is a variable condition, and lung function fluctuates throughout the day and across seasons.”
“What’s useful here is that the researchers have pinned down exactly when these variations occur, which can help refine diagnosis and management strategies. It highlights the importance of early detection, a message we’ve always emphasised in asthma care,” he said.
“More importantly, it serves as a reminder that patients need to understand their own rhythm — some may feel better at certain times and worse at others. Being aware of this can help them time their activities and even their inhaler use more effectively.”
(Edited by Muhammed Fazil.)
