Twenty-four-hour rhythm in the bronchial hyperreactivity to house dust in asthmatics.

Four subjects, 2 males (17 and 35 yr of age) and 2 females (24 and 47 yr of age) suffering from allergic asthma were studied for 10 days in allergen-shielded rooms and without medication. Synchronization of subjects to activity was by light on at 7 A.M. and sleep by light off at midnight. A single bronchial challenge to the threshold concentration of house dust, predetermined for each subject, was presented every other day at designated clock hours such that during a 10-day study span tests were presented at the following times: 8 A.M., 3 P.M., 7 P.M., and 11 P.M. The effect upon bronchial patency determined by FEV 1.0 15 min after house dust inhalation resulted in greatest effect at 11 P.M., while that at 8 A.M. resulted in least effect. The differences were statistically significant (p less than 0.025). Peak expiratory flow (PEF), self-measured at 3-hr intervals throughout the 10-day span, revealed practically no persistence of effect for inhalation of the house dust preparations at 8 A.M.; on the other hand, considerable persistence of effect on airway patency occurred from tests carried out at 11 P.M. The differences between the 24-hr rhythm-adjusted means (mesors) in the PEF for the (24-hr) spans following house dust inhalation at 8 A.M. and 11 P.M. were statistically significant (p less than 0.025) as well.