Prolonged cough research

The work started when we recognised that asthmatic subjects cough far more than healthy subjects do in response to inhaled mannitol, a sugar alcohol. Inhalation of mannitol powder increases the osmolarity of the airway lining fluid. Thereafter, the cough response to hyperosmolar airway challenges has been the principal focus of our group for over two decades. We have developed various novel methods, like hyperosmolar histamine challenge and hyperosmolar saline challenge with salbutamol pre-treatment. We have shown that the cough response to hyperosmolar saline correlates with the cough response to dry air hyperpnoea.

We have investigated the biochemical mechanisms of the response, the ability of the response to separate asthmatic and cough patients from healthy subjects, the ability of the response to predict the response to inhaled corticosteroids, the ability of the response to mirror the healing of cough, as well as the prognostic significance of the response. During all these years, we have co-worked with Dr. John Brannan’s group from Australia. Heikki Koskela worked with this group as a post-doc research fellow in 1997 – 1998.

In 2017, we performed a large cross-sectional study among all public service employees of two middle-sized towns in central Finland, Kuopio, and Jyväskylä. From the data of the 3695 responders, we have analysed the prevalence, risk factors, and consequences of prolonged cough. The consequences included, among others, doctor’s consultations and sick leave days due to cough, which have this far gained very limited attention. We have also revealed the association between certain triggers of cough and certain cough background disorders, like asthma. A novel finding was that family history of chronic cough is one of the risk factors for prolonged cough.

In 2018, we performed a follow-up survey in a subgroup of those participating in the 2017 survey to investigate the prognosis of the cough and the factors associated with it. We have also performed a cluster analysis in this population to define the cough phenotypes. Part of the subjects participating the 2017 survey have permitted us to utilise the information collected by Finnish health registries. By this means, we will further investigate the prognosis and the consequences of cough in the future.

Our group co-operates with Minna Purokivi’s group that investigates fibrosing lung diseases. They have prospectively recruited over 100 patients with fibrosing lung diseases and performed, among other samples, transbronchial cryobiopsies in each patient. Cough is one of the commonest symptoms in these patients. We will investigate the prevalence, mechanisms, and risk factors for cough in fibrosing lung diseases.

In 2020, we intend to start a new study in which we will recruit patients with recent-onset cough (3 – 8 weeks ago). This material would allow a unique opportunity to investigate why cough prolongs in certain subjects even for several years, causing substantial impairment in the health-related quality of life.