Matilde Valencia-Flores1, Babak Mokhlesi2, Victoria Santiago-Ayala3, Montserrat Reséndiz-García3, Alejandra Castaño-Meneses3, María Sonia Meza-Vargas4, Alejandro Mendoza3, Arturo Orea-Tejeda5, Guillermo García-Ramos6, Carlos Aguilar-Salinas7, Donald L Bliwise8. 1. 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. 2. Section of Pulmonary and Critical Care, Sleep Disorders Center, University of Chicago, IL, USA. 3. Clinica de Trastornos del Dormir, Departamento de Neurología y Psiquiatría, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán (INCMNCSZ), Mexico. 4. University of Manitoba Sleep Disorders Centre, Winnipeg, Manitoba, Canada. 5. Departamento de Cardiología, INCMNSZ, Mexico. 6. Departamento de Neurología y Psiquiatría, INCMNSZ, Mexico. 7. Departamento de Endocrinología, INCMNSZ, Mexico. 8. Sleep Program, School of Medicine, Emory University, Atlanta, GA, USA.
Abstract
BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSION: 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.
BACKGROUND: 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. METHODS: Seventy-eight obesewomen and men of similar age and body mass index living at altitude (Mexico City) underwent standard polysomnography, MWT, and completed validated sleep-related questionnaires. RESULTS: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. CONCLUSION: The ability to remain awake in obesepatients 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.