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A recent study conducted by researchers at the University of Cambridge reveals that the reliability of a lung function test used to diagnose asthma is significantly higher in the morning compared to later in the day. This finding emerges from the analysis of data collected from 1,600 patients as part of a database designed to enhance research and innovation in healthcare.
Asthma, a prevalent respiratory condition characterized by wheezing and difficulty breathing, affects approximately 6.5% of individuals over the age of six in the UK. Standard treatments often involve inhalers or nebulisers that deliver medication directly into the lungs.
Notably, asthma attacks tend to occur more frequently during the night or early morning hours. This pattern may be influenced by cooler nighttime air and increased exposure to allergens such as dust mites. However, it also points to the potential impact of circadian rhythms—our body’s natural internal clock—on asthma management.
The Victor Phillip Dahdaleh Heart and Lung Research Institute, in collaboration with the Royal Papworth Hospital NHS Foundation Trust, sought to investigate whether these circadian rhythms also affect the diagnostic capabilities of routine lung function tests for asthma. Typically, patients suspected of having asthma undergo spirometry testing, which measures lung function. Following this, they receive a bronchodilator medication like salbutamol, which helps to relax and open the airways. A significant change in spirometry results after medication indicates a high likelihood of asthma.
The Cambridge University Hospitals NHS Foundation Trust established the Electronic Patient Record Research and Innovation (ERIN) database to facilitate secure access to patient data for research purposes. Utilizing this innovative resource, the research team evaluated patient data from those referred to the Trust between 2016 and 2023, carefully adjusting for variables such as age, sex, body mass index (BMI), smoking status, and initial lung function impairment severity.
In their research published in Thorax, the team found a marked decline in the probability of a positive response to the lung function test as the day progressed. Specifically, for every hour post 8:30 AM, the likelihood of a positive response decreased by 8%. Dr. Ben Knox-Brown, the Lead Research Respiratory Physiologist at Royal Papworth Hospital, expressed surprise at how pronounced this effect was, stating, “Given what we know about the risk of an asthma attack fluctuating from night to day, we anticipated some variation, but the magnitude of the impact was unexpected.”
Dr. Knox-Brown emphasized the clinical significance of this timing effect, noting that conducting the test in the morning could yield a more reliable assessment of a patient’s response to asthma medication, which is vital for accurate diagnosis.
The researchers also highlighted a seasonal aspect to their findings, discovering that individuals tested in autumn were 33% less likely to show a positive result compared to those tested in winter. Dr. Akhilesh Jha, a Medical Research Council Clinician Scientist, posits that this variance may arise from various physiological factors influenced by seasonal changes.
“Our bodies operate on natural rhythms,” Dr. Jha explained. “Hormone levels fluctuate throughout the day, and our immune responses vary as well. Any of these elements could influence how patients react to lung function tests.” He noted that there is growing evidence that the timing of medical interventions, including vaccinations, can affect health outcomes, further underscoring the importance of considering the time of day and season when interpreting results from routine tests like spirometry.
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