Narcolepsy and odour: Preliminary report

Abstract

Introduction Narcolepsy is a primary sleep disorder characterized by excessive daytime sleepiness, sleep attacks, cataplexy, and sleep paralysis with hypnagogic hallucinations. The etiology of narcolepsy gives great importance to the role of the orexin/hypocretin system, both in animals and humans. The prevalence is 1/2000 in the general population and the diagnosis is based on clinical data and polysomnographic studies. Odours have been used as indicators of diseases dating back to traditional medicine. Dogs can be trained to detect any odorous substance even in the presence of other interfering odours. Numerous clinical studies based on scent detecting have been done with tumors and infections with a level of sensibility and specificity near 100%.This study has been carried out to test the clinical hypothesis of personal smell as a hint to the diagnosis of narcoleptic patients. Materials and methods Sweat samples from narcoleptic and controls were collected following the same protocol to avoid contamination, and tested independently by two trained dogs and their positive or negative detection compared to the gold standard diagnosis for narcolepsy. Neither trainer nor dog knew the source of the sample selected nor its placement in the search device. 12 narcoleptic patients, both sexes and various ages, diagnosed according to standard criteria, made up the patient group. The control group was made up of 22 healthy volunteer without sleep disorders, both sexes and various ages. The same samples were analyzed using Head Space-Solid Phase MicroExtraction and Gas Cromatography-Mass Spectrometry (HS-SPME–GCMS) and with proper statistical techniques to distinguish the aroma profile between the two groups. Results 11 narcoleptic were detected positive by the dogs while only three controls. HS-SPME—GCMS results showed that the disease can be discarded with a classification rate of 75%. HS-SPME–GCMS technique can be proposed as screening method in a first diagnosis approach. Conclusion It seems that narcoleptic patients have a distinct typical odour that trained dogs and analytical techniques can detect. The development of olfactory test for the diagnosis of narcolepsy opens a new research area. Acknowledgements This was not an industry supported study. The authors would like to thanks the Civil Guard for his contribution regarding the dog’s training and completion of the detection test for all the samples submitted. They have made this study possible.