The function test of the lung function used to help diagnose asthma works best in the morning, and becomes less reliable throughout the day, according to Cambridge researchers.
Using real world data of 1,600 patients, available through a database created to accelerate research and innovation, the team also found that their reliability differs significantly in winter compared to autumn.
Asthma is a common pulmonary condition that can cause wheezing and difficulty breathing, occasionally severe. About 6.5% of people over six years in the United Kingdom are affected by the condition. Treatments include the use of inhalers or nebulizers to transport medications to the lungs.
Most asthma attacks occur at night or later in the morning. Although this may be due in part to the coolest night air and exposure to mites and dust allergens, it also suggests that circadian rhythms, our ‘body watches’, probably play a role.
Researchers at Victor Phillip Dahdaleh Heart and Lung Research Institute, a collaboration between the University of Cambridge and the Royal Papworth Hospital NHS Foundation Trust (RPH), wanted to explore if these circadian rhythms can also have an impact on our ability to diagnose asthma, using clinical tests routine.
In general, people with asthma suspicion will be offered a spirometry test, which implies breathing deeply and then breathing and quickly during as long as possible in a tube to evaluate the lung function. Then the salbutamol drug will be administered through an inhaler or nebulizer, and shortly after resume the spirometry test.
Salbutamol works by opening the respiratory tract, so a positive result of the test, that is, a difference in the readings between the initial and monitoring spirometry tests, means that the respiratory tract must have been narrower or closer to begin with, which suggests that the patient could have asthma.
Cambridge University Hospitals NHS Foundation Trust (CUH) has recently established the research and innovation database of electronic patient records (ERIN) so that researchers can access patients data in a safe environment to help in their research and accelerate improvements in patient care.
Using this resource, the Cambridge team analyzed data of 1,600 patients referring to Cuh between 2016 and 2023, adjusted by factors such as age, sex, body mass index (BMI), the history of smoking and the severity of the initial deterioration in the pulmonary function.
In the findings published today in ChestThe researchers found that from 8.30 am, with every hour that happened during the working day, the possibilities of a positive response to the test, in other words, the patient’s lungs responded to the treatment, which suggests that they could have asthma, decreased by 8%.
Dr. Ben Knox-Brown, a respiratory physiologist for the main investigation in RPH, said: “Given what we know about how the risk of asthma attack changes between night and day, we expected to find a difference in the way people responded to the test of the lung function, but still, we were surprised by the size of the effect.
“This has potentially important implications. Testing in the morning would give a more reliable representation of a patient’s response to the medication than to do it in the afternoon, which is important when confirming a diagnosis such as asthma.”
The researchers also discovered that individuals had 33% less likely to have a positive result if they were tested during autumn compared to those tested during winter.
Dr. Akhilesh Jha, clinical scientist at the Medical Research Council at the University of Cambridge and Honorary Consultant in Respiratory Medicine in CuH, said there may be a combination of factors behind this difference.
“Our bodies have natural rhythms: our body registered,” Jha said. “Throughout the day, levels of different hormones in our bodies rise and fall and our immune systems work differently, for example. Any of these factors could affect the way people respond to the test of the pulmonary function.
“The idea that the time of day, or the season of the year, affects our health and how we respond to treatments is something we are seeing increasing evidence. We know, for example, that people respond differently to vaccines, depending on whether they are managed in the morning or afternoon. The results of our study support this idea and can take into account when they interpret the results of these common tests.”