Raynaud's disease is a classic, if relatively benign, example. Occurring largely in young healthy women with no organic arterial lesions, the condition is believed to represent an exaggeration of the normal vasomotor response to cold or emotion. Its occurrence in patients with migraines and variant angina has suggested a common predisposing cause for vasospasm. In Raynaud's phenomenon, arterial narrowing occurs secondary to scleroderma, lupus or other systemic diseases, and patients are more likely to suffer long-term sequelae, including chronic skin and nail changes and muscle atrophy. In some patients, Raynaud's phenomenon may be due to chronic cold agglutinin disease, characterized by clotting and hemolysis in tissues exposed to cold and chronic hemolytic anemia exacerbated by low temperatures.
Most asthmatic patients know the hazards of breathing cold air, particularly during exercise.
Post-exertional obstruction increases at higher levels of exertion and when the inspired air is cold and dry. Winter activities like ice hockey, skating and cross-country skiing are thus more likely to induce asthma attacks than activities of similar intensity performed in warm environments. Although smooth-muscle contraction and mucus accumulation may be involved, many experts have hypothesized a role for the bronchial vasculature. Most excess thrombotic deaths appear to be due to brief outdoor exposure rather than to prolonged exposure in inadequately heated homes. Thus, although seasonal patterns in respiratory infections and in behavioural and humoral factors may play a role, what occurs acutely on exposure to the cold appears important.