MedPage Today has outlined a published clinical case that suggests an association between changes in weather and acute severe asthma exacerbations. Low temperatures or a sudden drop can trigger asthma exacerbations by provoking aggravated airway spasms by airway cooling or irritation. The case authors cite several studies that have identified exposure to cold air as one of the causes of airway contractions and asthma attacks and are a trigger of childhood asthma. Notably, research performed in Shanghai identified cold air as the most important trigger of asthma exacerbation, exceeding the effects of respiratory infection, dust, and exercise. Severe asthma is defined as asthma that remains uncontrolled despite adherence to maximal optimized therapy, or that worsens when high-dose treatment is tapered. This relatively small proportion of asthma patients -- representing 3%-10% of adults with asthma worldwide -- is more prone to recur­rent and potentially life-threatening exacerbations, thus accounting for a large burden of morbidity and mortality, and more than 60% of the total medical cost of asthma care. Get the full story at medpagetoday.com.