Key result
Early chronotypes reached their maximum peak expiratory flow rate three hours earlier than late chronotypes (P=0.003), while late chronotypes exhibited a stronger morning bronchodilator response to theobromine.
Why the study?
The influence of morningness-eveningness preference and dietary components on the circadian variation in peak expiratory flow was not fully understood.
Does theobromine affect the 24-h variation in peak expiratory flow rate differently in early versus late chronotypes in healthy young females?
Observational (n=97)
No
Does theobromine affect the 24-h variation in peak expiratory flow rate differently in early versus late chronotypes in healthy young females?
The timing of maximum peak expiratory flow differs by chronotype, and responsiveness to theobromine varies accordingly, suggesting chronotype should be considered for respiratory drug timing.
Answers are grounded in this paper and cite their sources.
Chronotype modulates PEF rhythm and theobromine response in healthy females; leaves open whether this informs drug timing in respiratory disease.
The influence of morningness-eveningness preference and dietary components on the circadian variation in peak expiratory flow (PEF), an established criterion for pulmonary function, is not fully understood. This study aimed to investigate (a) how the chronotype influences the 24-h variation in PEF and (b) whether the bronchodilator theobromine affects this variation differently in different chronotypes. Ninety-seven healthy non-smoking females (54 early chronotypes, ET; 43 late chronotypes, LT; 18–35 years) recorded their PEF over 24 hours at 4-h intervals (08:00/12:00/16:00/20:00/24:00/04:00/08:00 h). In a subgroup (26 ET, 18 LT), the effect of 48 mg theobromine (40 g dark chocolate) on PEF was compared on three consecutive 24-h days with no administration, morning administration and evening administration of theobromine. Repeated measures ANOVA tested for 24-h variation in PEF. Both chronotypes displayed significant 24-h variation in PEF (P < 0.0001) explaining 36% (ET) and 31% (LT) of variance of PEF. The time of maximum PEF was three hours earlier in ET than in LT (P = 0.003) and correlated negatively with chronotype scores (P = 0.001) and positively with bedtimes (awakening time: P < 0.001; sleep-onset time: P = 0.012). The chronotypes showed no differences in 24-h mean and amplitude % mean for PEF. Administration of theobromine strengthened the morning increase (P = 0.004) and weakened the evening decrease (P = 0.063) of PEF in LT, but had no effect in ET. The differences found between chronotypes in timing of maximum PEF and responsiveness to the bronchodilator theobromine might have clinical relevance. Therapy for respiratory diseases should consider the chronotype of patients for drug timing and dosage.
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Köhlmoos et al. (2025) conducted an observational in Healthy adults (n=97). Early chronotype vs. Late chronotype was evaluated on Time of maximum peak expiratory flow (PEF) (3 hours earlier, p=0.003). Early chronotypes reached their maximum peak expiratory flow rate three hours earlier than late chronotypes (P=0.003), while late chronotypes exhibited a stronger morning bronchodilator response to theobromine.
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