Regina Chand, a medical writer
from Edmonton, flew to Seattle two weeks ago to cover
the 2004 CHEST meeting. She could put up with the subpar
airline service and food, but the long trip also played
havoc with her sleep. Despite feeling sluggish from the
jet lag, she was glad that she didn't miss any of the
presentations she signed up for. To her surprise she learnt
that circadian rhythms might do more than dictate sleep
patterns — they could also affect how she controls
her asthma.
New research reported at the CHEST
2004 meeting in late October claimed that circadian
rhythms have a profound effect on lung function. This
finding could have major implications for the management
of asthma and chronic obstructive pulmonary disease.
Researchers found that the late afternoon, when many
of us are at our groggiest, is precisely when the lungs
are operating at peak efficiency.
"We often associate the end of
the work day with being tired and less motivated for
physical exertion; however, lung function seems to be
at its best during this time. As a result, exercising
or engaging in other physical activities in the late
afternoon may help us to achieve optimal performance,"
said Dr Boris Medarov of the Long Island Jewish Medical
Center.
The study is based on lung function
tests of 4,835 patients over five years, conducted at
different periods of the working day. Measurements included
forced expiratory volume, full vital capacity and total
lung capacity. When the results were analysed by time
of day, a clear pattern emerged.
Airway obstruction tended to worsen
throughout the morning, reaching a peak at about noon.
After that, said Dr Medarov, breathing began to improve,
and was at its easiest between 4pm and 5pm.
Knowing the effects of circadian
rhythms on lung function could help patients better
manage their breathing problems, he told the conference.
"Many patients with asthma and chronic obstructive pulmonary
disease administer bronchodilators around the clock,
when they actually may need less treatments and a different
regimen that includes administering the medication at
midday when their lung function is at its lowest. It
also may be better to extubate patients in the late
afternoon when their lung function is at its best."
He added that circadian rhythms
governing lung function might potentially be influenced
by biofeedback or relaxation techniques, offering a
new approach to disease management.
Dr Paul Kvale, President of the
American College of Chest Physicians, endorsed the study's
findings. "Circadian rhythms can greatly influence how
patients with respiratory conditions respond to certain
therapies. By knowing how the respiratory system naturally
responds at different times during the day, healthcare
providers can adapt treatments and procedures to better
fit patients' individual needs."
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