Inflammation in nocturnal asthma?

Abstract

At present there is some indirect evidence for increased nocturnal inflammation in patients suffering from nocturnal asthma: 1. Circulating eosinophil numbers and activation, as reflected by increased levels of ECP and EDN and low-density eosinophils, are increased at night. 2. Circulating histamine levels are increased at night. 3. Hyperresponsiveness to AMP at night is increased compared with hyperresponsiveness to methacholine. However, most results of various studies point to nocturnal asthma's being an expression of more severe asthma: 1. Both AMP and propranolol responsiveness, indirect measures of airway hyperresponsiveness, are lower both at 4:00 A.M. and 4:00 P.M. in asthmatics with nocturnal asthma than those without nocturnal asthma. 2. Patients with nocturnal asthma have higher circulating numbers of eosinophils at both 4:00 A.M. and 4:00 P.M. than those without nocturnal asthma, and eosinophil survival is not different at these times. 3. Patients with nocturnal asthma have higher PGD2 levels in BAL both at 4:00 A.M. and 4:00 P.M. than those without nocturnal asthma, but show no significant difference between levels at these two times. 4. Two studies have shown no difference in BAL eosinophil numbers and activation parameters at night in nocturnal asthma. 5. Histamine levels in BAL fluid are comparable day and night in patients with and without nocturnal asthma. 6. Inflammatory mediators in BAL are higher in asthmatic patients than in normal subjects, but are not different between patients with and without nocturnal asthma. Thus, patients with nocturnal asthmatic symptoms show an overall increased burden of mediators released from mast cells and other inflammatory cells. In conclusion, we feel that the term "nocturnal asthma" is misleading, in that it does not describe a unique entity in certain patients with asthma. We prefer, in view of the previous arguments, to consider nocturnal asthma a mere expression of more severe asthma. Thus we suggest the term "nocturnal asthma" be changed to "asthma with nocturnal symptoms."