Influence of the device used for obstructive sleep apnea diagnosis on body position: a comparison between polysomnography and portable monitor.

PURPOSE: Different devices have been used for the diagnosis of obstructive sleep apnea (OSA), which differ in the number of sensors used. The numerous sensors used in more complex sleep studies such as in-lab polysomnography may influence body position during sleep. We hypothesized that patients submitted to in-lab polysomnography (PSG) would spend more time in the supine position than patients submitted to an ambulatory Portable Monitor (PM) sleep study. METHODS: Body position during PSG and PM studies was compared among two distinct groups of patients matched for age, body-mass index (BMI), apnea-hypopnea index (AHI), and gender. Predictors of time spent in the supine position were determined using a multiple linear regression model. RESULTS: Of 478 participants who underwent either PSG or PM studies, mean age: 61[43-66] years; males: 43.9%; BMI: 28.4[26.1-31.1]kg/m2; AHI 14[7-27] events/hour). Participants who underwent PSG studies spent more time in the supine position (41[16-68]% than participants who underwent PM studies (34[16-51]%), P = 0.014. Participants with OSA spent more time in the supine position than participants without OSA, both among the PSG and PM groups P < 0.05). Gender, BMI, OSA severity, and sleep study type were independent predictors of time spent in the supine position. CONCLUSION: In-lab PSG may increase time spent in the supine position and overestimate OSA severity compared to a PM sleep study. OSA diagnosis is also associated with increased time spent in the supine position. The potential influence on the sleeping position should be taken into account when choosing among the different sleep study types for OSA diagnosis.

Muscle and visceral fat infiltration: A potential mechanism to explain the worsening of obstructive sleep apnea with age.

STUDY OBJECTIVES: Aging is a major risk factor for obstructive sleep apnoea (OSA) and is associated with increased upper airway collapsibility, but the mechanisms are largely unknown. We hypothesized that the increase in OSA severity and upper airway collapsibility with age are partially mediated by upper airway, visceral and muscle fat infiltration. METHODS: Male subjects underwent full polysomnography, upper airway collapsibility determination (Pcrit) after sleep induction with midazolam, upper airway and abdominal computed tomography. Tongue and abdominal muscle fat infiltration were assessed by the determination of muscle attenuation with computed tomography. RESULTS: Eighty-four males with a wide range of age (47 ± 13 years, range 22-69 years) and apnea-hypopnea index (AHI) (30 [14-60] events/h, range 1-90 events/h), were studied. Younger and older males were grouped according to the mean age. Despite similar body mass-index (BMI), older subjects had higher AHI, higher Pcrit, larger neck and waist circumference, higher visceral and upper airway fat volumes (P < 0.01) as compared to younger subjects. Age was associated with OSA severity, Pcrit, neck and waist circumference, upper airway fat volume and visceral fat (P < 0.05), but not with BMI. Older subjects had lower tongue and abdominal muscle attenuation as compared to younger subjects (P < 0.001). Age was inversely associated with tongue and abdominal muscle attenuation, indicating muscle fat infiltration. CONCLUSIONS: The associations between age, upper airway fat volume, visceral and muscle fat infiltration may help to explain the worsening of OSA and increased upper airway collapsibility with aging.