RELATIONSHIP OF PLASMA EPINEPHRINE AND CIRCULATING EOSINOPHILS TO NOCTURNAL ASTHMA

The mechanisms of nighttime airway obstruction are not fully establish ed, but include circadian fluctuations in epinephrine and cortisol. To evaluate the relationship of circadian patterns in epinephrine and co rtisol to nighttime airflow obstruction, 10 young adult asthma patient s (ages 19 to 25 yr) were admitted to a hospital clinical research uni t for a 3-day study during which plasma concentrations of epinephrine, cortisol, and histamine were determined along with white blood cell a nd eosinophil counts every 6 h (1600, 2200, 0400, and 1000 h). Six of the 10 patients experienced at least one episode of nocturnal asthma ( defined by more than a 15% decrease in antemeridian (A.M.) to postmeri dian (P.M.) FEV(1) values). Plasma epinephrine levels (pg/ml) showed a circadian pattern, and the concentration at 2200 h was significantly (p = 0.039) different for the nocturnal and non-nocturnal asthma group s. Circulating eosinophil numbers were greater in subjects who had mor e frequent episodes of nocturnal asthma, and correlated with the frequ ency of nocturnal asthma (r = 0.732, p = 0.02, Spearman rank correlati on) and average percent decrease in FEV(1) (r = 0.667, p = 0.035). Pla sma cortisol concentrations also showed circadian patterns, but no dir ect association with nocturnal asthma; plasma histamine concentrations showed no circadian patterns and no association with nocturnal asthma . Our findings indicate that changes in plasma epinephrine precede the development of nocturnal airway obstruction and contribute to the lik elihood of nighttime airflow obstruction.