Time-of-day has no effect on exercise-induced bronchoconstriction in mild to moderate asthma

Title: Time-of-day has no effect on exercise-induced bronchoconstriction in mild to moderate asthma
Author(s): A Rowe N Fleming B Donne N Mahony
Institution: Human Performance Laboratory, Discipline of Anatomy, Watt's Building, Trinity College Dublin
Poster: Click to view poster
Category: COPD/Asthma
Abstract: Introduction:

Exercise-induced bronchoconstriction (EIB) is defined as a
transient, acute narrowing of the airway associated with
▪ Exercise is therapeutic for asthma, however up to 90% of
asthmatics experience exercise-induced
bronchoconstriction (EIB)
▪ Diurnal variation in symptoms is characteristic of asthma
but few studies have evaluated whether this occurs in EIB.
▪ Eucapnic Voluntary Hypernea (EVH) is a indirect
bronchoprovocation test where participants maximally
respire a dry gas to stimulate exercise.

▪ To establish the effect of diurnal variation in EIB in a cohort
of recreationally-active males with a diagnosis of mild to
moderate asthma.


Asthmatics (n=14) were male, recreationally active,
diagnosed with mild to moderate asthma by a physician
and used an inhaler with exercise.
▪ Controls (n=9) were recreationally-active volunteers who
had no history or symptoms of asthma.
▪ Participants were randomised to either complete an AM
(07:00 to 08:00) or PM (17:00 to 18:00) EVH challenge first,
followed by the alternate test 34 h to 7 days later.
▪ The EVH protocol comprised of six-minutes of
hyperventilation of a 5% CO2
gas at a minimum ventilation
rate of 21 × FEV1 min-1.
▪ A 2-way repeated measures ANOVA was performed to
assess for AM/PM differences in response to EVH.
▪ The primary outcome measure was FEV1 pre- and post-EVH.

No difference between baseline FEV1 in asthmatics (4.21
± 0.79 vs. 4.25 ± 0.65L) was observed between AM and
PM tests.
▪ Significant reductions from baseline FEV1 were noted in
both cohorts post-EVH(P<0.001) (Figure 1).
▪ 64% (n = 9) of asthmatics had at least one positive EVH
test (10 % drop in FEV1 post-EVH at one time point).
▪ No positive tests were noted in controls.
▪ The mean maximum drop in FEV1 for asthmatics was 15.1
± 15.4 vs. 15.0 ± 14.6% for AM and PM tests (Figure 2).
▪ No significant differences were observed in controls.
▪ A repeated-measure 2-way ANOVA showed no effect of
time-of day on FEV1 post-EVH in asthmatics.

▪ We demonstrated diurnal variation has no effect in a
cohort of males with mild-to-moderate asthma.
▪ This was the first study to use the gold-standard protocol
to test for diurnal variation.
▪ Our study adds to previous work showing no diurnal
variation (1) and contrasts with one study which reported
more EIB in the evening (2).
▪ Our cohort had milder asthma with no baseline variability
in FEV1 – results may have differed in a more severe
▪ Given the beneficial effects of exercise on asthma, we
recommend asthmatics exercise at the time-of-day they
are most likely to exercise