A collaborative effort between the University of Córdoba and IMIBIC uses, for the first time, changes in sweat metabolism to diagnose the severity of sleep apnea
In GREEK, stillness (ἠπνοια) denotes “absence of breath”. Therefore, obstructive sleep apnea is a disease defined by interruptions in breathing, which recur while the person suffering from it is asleep. Feeling short of breath, fatigue and sleepiness are symptoms suffered by patients. This disease is also associated with the incidence of cardiovascular disorders, so to deal with these related problems, an adequate diagnosis of the severity of the disease is necessary.
Changes in the metabolism of people with sleep apnea are the key to determining the severity of the disease. These changes are usually analyzed in blood or urine. However, in search of a less invasive and more accessible alternative, a team from the Department of Analytical Chemistry of the University of Córdoba and the Institute of Biomedical Research Maimonides in Córdoba (IMIBIC), formed by researchers Laura Castillo, Mónica Calderón, Feliciano Priego. and Bernabé Jurado, verified, for the first time, the ability of sweat samples to ascertain the severity of sleep apnea.
“By analyzing the metabolism of sweat and its changes, especially at night, we were able to see what stage of the disease the patients were in,” explains Laura Castillo, lead author of the study. For her, the advantages of using sweat over other samples are clear: “it is a non-invasive and clean sample since, unlike the case with blood, we do not need to remove proteins and it is much easier to analyze and detect metabolites. “
In this study, sweat samples before and after sleep were analyzed from a series of people with sleep apnea at different stages, as well as from a control group without the disease.
In these samples, using the technique of gas chromatography, combined with high-resolution mass spectrometry, 78 metabolites were identified and their changes, mainly related to energy production and oxidative stress, were studied. “We were able to see how the sweat metabolism itself shows these changes during sleep, causing the person’s energy production to deteriorate and their oxidative stress to increase,” says Castillo. Thus, with a personalized monitoring using the sweat secreted during the sleep of a person with the disease, its development can be monitored and its possible effects such as cardiovascular problems monitored. This metabolic profile also made it possible, in the trial, to distinguish between those who had the disease and those who did not and belonged to the control group.
An index to learn more about the disease
In addition to establishing sweat as a good sentinel when it comes to determining the stage of the disease, this work also reveals the importance of considering the oxygen desaturation index when diagnosing it.
The diagnosis of sleep apnea is currently based on the Apnea-Hypopnea Index (AHI), which measures sleep apnea based on the number of breathless episodes a person experiences per hour (for example, the disease is severe when they have 30 or more episodes per hour time). According to the team, this index “does not provide all the information about the patient’s disease or condition at a given time,” as it measures how many events there are, but not their severity.
Therefore, in their study they also verify the importance of using the oxygen desaturation index, which indicates how severe the episodes are by counting the number of events in which oxygen saturation has decreased by more than 3%. After verifying the linear relationship between this index and the AHI, its validity was confirmed, since, in addition to the data provided by the AHI, it also measures the severity, taking into account the loss of oxygen saturation.