CHARACTERISTICS AND PROGNOSTIC VALUE OF MORNING DIPPING OF PEAK EXPIRATORY FLOW-RATE IN STABLE ASTHMATIC SUBJECTS

Characteristics and prognostic relevance of morning dip of peak expiratory flow rate (PEFR) were evaluated in stable asthmatic subjects. Among 246 outpatients monitored 4 times daily for 2 wk, 38 (group A) showed a significant difference between morning reading of PEFR and each of the others; they were compared to 38 randomly selected patients (group B) not showing morning dip in PEFR. Less frequent seasonal course, extrinsic pathogenesis and sensitization to mites characterized group A; starting airflow limitation was more severe in those with morning dip, but no significant difference between mean PEFR measured throughout 2 wk was found. At 6-12 wk, morning dip was not found in 19 of 38 subjects in group A and appeared in 7 of 38 subjects in group B, with no clearcut relationship to treatment being evident. At 25-104 wk, no significant difference between therapeutic requirements and the forced expiratory volume in 1 s was detected; therefore, unlike the short-term, morning dip is not a risk factor for worse long-term prognosis.