Among respiratory symptoms, wheeze associates most strongly with impaired lung function in adults with asthma: a long-term prospective cohort study.

Background: Asthma is a common disease and a major public health concern. Respiratory symptoms are related to its prognosis, which in turn associates with lung function. Still this association on a long-term basis is not entirely understood.

Aim: To study the association of the type and number of respiratory symptoms with FEV and FEV decline in women and men with asthma.

Method: A population-based cohort of adults with asthma was examined at study entry between 1986 and 2001 and at follow-up between 2012 and 2014, and n=977 had valid measurements of FEV on both occasions. Data regarding respiratory symptoms at study entry (recurrent wheeze, dyspnoea, longstanding cough and productive cough) were analysed in relation to FEV and annual decline in FEV, both unadjusted and adjusted for other potentially associated factors by linear regression.

Results: For both sexes recurrent wheeze and dyspnoea were associated with lower FEV at study entry and follow-up, while productive cough was associated with lower FEV only at follow-up. No associations were found between the type of symptoms and annual decline in FEV. In adjusted analyses, the association between recurrent wheeze and lower FEV both at study entry and follow-up remained significant among women. Also, the association between a higher number of symptoms with lower FEV both at study entry and follow-up were present for both sexes and remained after adjustment.

Conclusions: Particularly recurrent wheeze and a higher number of respiratory symptoms may predict lower lung function also in the long run among women and men with asthma.