Smelling test may help to detect Parkinson’s at an early stage


Smelling tests offer a completely new way to detect Parkinson’s at an early stage so treatment can be commenced as soon as possible. This method utilises the fact that an impairment of the sense of smell can be an early sign of this neurological disease. Smelling tests conducted in public places have yielded impressive results, neurologists from Cologne, Germany, reported at the meeting of the European Neurological Society (Prague, Czech Republic, 9–12 June 2012).

Although Parkinson’s is incurable, today’s therapies enable the course of the disease to be favourably influenced and patients to have a high quality of life for many years. The disease must be detected early to counter the destruction of brain cells but there are still no sufficient strategies for early detection. The sense of smell provides valuable indications. The loss of this sense for no known cause (hyposmia) can be interpreted as one of the non-motor signs for Parkinson’s disease.

Ulrich Liebetrau, chief physician for Parkinson’s consultations at the Neurological Department of Kliniken der Stadt Köln, Germany, said at the 22nd Meeting of the European Neurological Society: “Smelling tests in doctors’ offices are suitable for detecting hyposmia but so too are tests conducted in public places such as pedestrian zones.” 

“Our objective was to reach as many people with hyposmia as we possibly could,” said Liebetrau. The method used was unusual. The researchers conducted a public smelling test on a Saturday with the support of Farina, the producer of the original Eau de Cologne. The venue was Gürzenich, a banqueting hall in Cologne’s pedestrian district well-known from the Cologne Carnival. The physician described the requirements the venue had to meet: “For people to accept the test we were offering, the location had to be central and familiar to everyone. Another important factor was having private places to withdraw. But tents would have detracted from the seriousness of the endeavour.” People were given vanilla, lemon, cloves and lavender to smell.


Of the 187 people who accepted the invitation to take a smelling test, 46 patients were identified as having hyposmia. All of them were offered a follow-up examination at a facility of the City of Cologne Clinics (Kliniken der Stadt Köln). Liebetrau commented: “The test was to be followed up by a professional examination done by neurologists and ENT specialists at a separate time and place. After all, hyposmia can be a sign of any number of diseases.” One possibility is that the loss of the sense of smell is a sign of Parkinson’s. This was the case for three individuals, who had no knowledge before the test that they had this disease.

Low-threshold tests make it possible to detect diseases in the first place that can otherwise become chronic if patients procrastinate. Researchers consider this to be a main advantage of these tests for patients. Early diagnosis is an advantage even if severe neurological disorders such as Parkinson’s are detected. “There is no cure for Parkinson’s but new drugs such as Rasagilin can have a demonstrably positive effect on the course of the disease, especially if treatment is started early. Further research is needed to determine whether that also applies to early stages of the disease.”

The authors of the study concluded that olfactory dysfunctions are not just an irritating malady but also offer an opportunity for early detection of Parkinson’s. They therefore recommend that hyposmia become better known as an early indicator of Parkinson’s. Liebetrau adviced: “Physicians should ask more frequently about olfactory dysfunctions and conduct simple tests, for instance with coffee or spices. If hyposmia is suspected, a confirmation test must be carried out.” He added that public smelling tests are especially suitable for raising awareness of hyposmia.