Participants measured their lung function tid: morning (5:00 am-11:59 am), afternoon (12:00 pm-7:59 pm), and evening/night (8:00 pm-4:59 am), for about 21 days. Peak expiratory flow (PEF) and FEV1 were measured using an electronic pocket spirometer (Asthma Monitor AM2; Jaeger/Toennies; Hoechberg, Germany) according to standards of the European Respiratory Society.12 After the self-assessment, the participants’ PEF value was displayed on the screen. The device included an electronic diary, which presented a number of questions to participants before any lung function measurements could be made. Once these ratings were completed, the participants were not able to access them for further review. The questions (rated on a scale from 1-4) included (1) current shortness of breath, with four answer alternatives: none, mild, moderate, severe; and (2) physical activity level in the past 30 min, with four answer alternatives: none (eg, lying, sitting still, standing still), mild (eg, normal walking, light manual work at the desk such as writing, typing), moderate (eg, fast walking, climbing a few flights of stairs, lifting or carrying heavier items), or heavy (eg, running [eg, for bus, train], fast uphill walking, climbing several flights of stairs, lifting or carrying several heavier items, dancing, physical exercise, or sports). Additionally, we analyzed participants’ social activity in the past 30 min, with four alternatives: alone, mostly alone, mostly with others, and always with others (for each alternative, participants were given detailed examples at the beginning of the diary period). Participants also pressed a marker each time they used their bronchodilator. This was used as a covariate in the analysis by assigning it a code of 0 to 6, reflecting how recently the bronchodilator was used (0 = > 6 h earlier, 6 = last hour). The number of days that participants completed ranged between 19 and 45. There were no significant group or time-of-day differences in the number of recorded self-assessments.