Intermittent hypoxemia and sleep fragmentation: associations with daytime alertness in obese sleep apnea patients living at moderate altitude.
Although obstructive sleep apnea (OSA) has long been associated with daytime sleepiness, far less is known about its association with the ability to remain awake. The aim of this study was to examine the relative importance of inter-correlated measures of OSA severity (eg, various indices of oxygen saturation and sleep fragmentation) in the ability to stay alert as measured objectively by the Maintenance of Wakefulness Test (MWT), defined by a mean sleep latency of ≥12 min.



Seventy-eight obese women and men of similar age and body mass index living at altitude (Mexico City) underwent standard polysomnography, MWT, and completed validated sleep-related questionnaires.



Men had more severe sleep apnea than women (p = 0.002) and were also less alert on MWT (p = 0.022). Logistic regression models indicated that measures of desaturation consistently predicted MWT-defined alertness, whereas varied measures of sleep fragmentation did not. Nearly a third of the variance (r(2) = 0.304) in MWT-defined alertness was accounted for by the number of desaturations per hour of sleep (p = 0.003), which is considerably higher than other studies have reported in different populations.



The ability to remain awake in obese patients is best accounted for by hypoxemia rather than sleep fragmentation. Whether the size of this effect reflects differences in the population under study (eg, extent of obesity, racial background, residence at moderate altitude) and/or is a function of the measurement of alertness with the MWT remains uncertain.
Clinica de Trastornos del Dormir, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNCSZ), Mexico; División de Investigación y Estudios de Posgrado, UNAM, Mexico. Electronic address: valflor@unam.mx.
Matilde
M
Valencia-Flores
Section of Pulmonary and Critical Care, Sleep Disorders Center, University of Chicago, IL, USA.
Babak
B
Mokhlesi
Clinica de Trastornos del Dormir, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNCSZ), Mexico.
Victoria
V
Santiago-Ayala
Clinica de Trastornos del Dormir, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNCSZ), Mexico.
Montserrat
M
Reséndiz-García
Clinica de Trastornos del Dormir, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNCSZ), Mexico.
Alejandra
A
Castaño-Meneses
University of Manitoba Sleep Disorders Centre, Winnipeg, Manitoba, Canada.
María Sonia
MS
Meza-Vargas
Clinica de Trastornos del Dormir, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNCSZ), Mexico.
Alejandro
A
Mendoza
Departamento de Cardiología, INCMNSZ, Mexico.
Arturo
A
Orea-Tejeda
Departamento de Neurología y Psiquiatría, INCMNSZ, Mexico.
Guillermo
G
García-Ramos
Departamento de Endocrinología, INCMNSZ, Mexico.
Carlos
C
Aguilar-Salinas
Sleep Program, School of Medicine, Emory University, Atlanta, GA, USA.
Donald L
DL
Bliwise
D000328:Adult; D000531:Altitude; D005260:Female; D006801:Humans; D000860:Hypoxia / Q000150:complications*; D008297:Male; D008800:Mexico; D009765:Obesity; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000150:complications*; D012894:Sleep Stages / Q000502:physiology; D011795:Surveys and Questionnaires; D014851:Wakefulness / Q000502:physiology*
Alertness; Intermittent hypoxemia; MWT; Obesity; Sleepiness; Wakefulness