Timing, Sleep, and Respiration in Health and Disease - Progress in Molecular Biology and Translational Science - page 208

5.2. Asthma
Several factors discussed above are relevant to asthma. First of all, the normal
variation in airway tone and airway caliber that occurs in most people is par-
ticularly troublesome, even life threatening, in asthmatics since they have a
narrowed airway to begin with. Second, the circadian variation in sensitivity
to respiratory stimuli can be bothersome. In one study of six asthmatics with
known nocturnal worsening and four healthy controls, there was a night-
time increase in lower airway resistance as evidenced by a reduction in
FEV 1 , in asthmatics compared to controls. This change occurs irrespective
of sleep state, but is enhanced during nighttime sleep. Despite the changes in
airway resistance, subjects maintained minute ventilation largely by increas-
ing RR, suggesting that the compensatory ventilator response to the
increased resistance is not lost during sleep. 194 In addition to the variations
in airway resistance and irritant sensitivity, there can be circadian influence
on asthma in a number of ways including circadian variations in circulating
catecholamines, circulating eosinophils and neutrophils, mast cell mediator
response, adrenergic tone, cortisol level, cholinergic function. 114

5.3. Epilepsy
Seizures can be associated with profound respiratory dysfunction, including
apnea, with associated hypoxemia and hypercapnia. 195-199 This can contrib-
ute to SUDEP. SUDEP is the leading cause of death in patients with epi-
lepsy. 200 There is still a great deal to be learned about the risk factors and
pathophysiology of SUDEP; however, it is thought to ensue from a primar-
ily respiratory, cardiac, autonomic, or electrocerebral etiology. 201-203
SUDEP tends to occur at night and it has been proposed that there may
a circadian- and/or sleep-state dependence to SUDEP. 204,205 One could
postulate that death could ensue if a seizure occurred in a susceptible indi-
vidual at a time in the circadian cycle or sleep cycle in which the respiratory
rhythm was already unstable or when the ð P CO 2 Þ was already elevated.

5.4. Sudden infant death syndrome
SIDS is defined as the sudden death of an infant under a year of age that
remains unexplained after autopsy, death scene investigation, and review
of the clinical history. 206 In the triple risk model of SIDS, a susceptible baby
experiences an environmental challenge during a critical developmental
time period. The preponderance of data suggests that susceptible babies
are ones that have abnormalities of their brainstem serotonergic