Asthma control and cold weather-related respiratory symptoms

In the northern hemisphere people are exposed recurrently to cold air and asthmatics experience more respiratory symptoms. We hypothesized that subjects with poor asthma control are more prone to experience cold weather-related respiratory symptoms than those with good asthma control.

A population-based cross-sectional study of 1995 adult asthmatics (response rate 40.4%) living in the Northern Finland was conducted using a questionnaire where cold weather-related respiratory symptoms as well as questions related to asthma control were inquired. The Asthma Control Test (ACT) was defined based on five questions (disadvantage and occurrence of asthma symptoms, waking up because of asthma symptoms, use of rescue medication and self-assessment of asthma control during the past 4 weeks), and was divided into quartiles.

Cold weather-related respiratory symptoms were more frequent among asthmatics with poorly controlled asthma (ACT Q1 vs. ACT Q4); adjusted prevalence ratio (PR) for shortness of breath (men 1.47, 95% confidence interval 1.22-1.77; women 1.18, 1.07-1.30), cough (men 1.10, 0.91-1.34; women 1.18, 1.08-1.30), wheezing (men 1.91, 1.31-2.78; women 1.48, 1.17-1.87), phlegm production (men 1.51, 1.06-2.14; women 1.62, 1.27-2.08) and chest pain (men 4.47, 1.89-10.56; women 2.60, 1.64-4.12). The relations between asthma control and symptom occurrence seemed stronger among smokers than never smokers and subjects with body mass index (BMI) below and above 25-30.

Our study provides new evidence that subjects whose asthma is poorly controlled are more prone to experience cold weather-related respiratory symptoms and even a slight worsening of asthma control increases symptom prevalences.