Nocturnal waking and morning dip of peak expiratory flow in clinically stable asthma patients during treatment. Occurrence and patient characteristics.

The occurrence of nocturnal waking due to asthma and morning dip of the peak expiratory flow (PEF), and the associated patient characteristics were investigated in 103 clinically stable asthmatic patients from a pulmonary outpatient clinic. Analysis of a 1 week diary showed a mean week morning PEF dip (i.e. morning/daytime highest PEF) of 12%. A mean dip of > or = 20% was found in 20% of the patients. Three groups were distinguished: 10% were 'nocturnal-waking patients' (waking up > or = 2 nights a week with a PEF dip of > or = 20%); 19% 'morning-dipping patients' (patients with > or = 3 dips a week of > or = 20% but with waking up on < 2 nights a week) leaving 71% 'remaining patients'. 28% of all patients showed morning PEF dips. In a questionnaire, waking every night was reported by 9%, at least once a week by 42% and once a month by 72%. In 'nocturnal-waking patients' FEV1 and morning and evening PEFs were lower than in 'remaining patients'; complaints during the night and on rising were more severe. The morning PEF dip was the same in 'nocturnal-waking patients' and 'morning-dipping patients'. The occurrence of waking was the same in 'morning-dipping patients' and in the 'remaining patients'. There were no differences in other clinical parameters among the three groups. We conclude that a subset of clinically stable asthma patients presents morning dips and nocturnal waking. They do not differ substantially from the remaining patients in other clinical characteristics.