The interaction between comorbidities and sleep stages influences oxygen re-saturation characteristics

Sleep stages exhibit differing patterns of cardiac, respiratory and nervous system activation. Rapid eye movement (REM) sleep is associated with deeper oxygen desaturation events in obstructive sleep apnea. However, no studies have looked to the effect of sleep staging on re-saturation characteristics. Polysomnographic data from the Sleep Heart Health Study were utilised to derive oxygen saturation parameters from events having both desaturation and re-saturation parts. Sleep stages were described as non-REM (NREM) 1 or 2 (combined), 3 and REM. Sleep stage effects on desaturation and re-saturation characteristics were investigated in a healthy subgroup (n = 759) and participants with hypertension (n = 2534), lung disease (n = 715), heart failure (n = 199) and myocardial infarction (n = 713). A total of 3793 participants (48.3% female) were included for analysis (171,976 saturation events; median 20 per participant). Events during REM had the longest duration, deepest nadirs and greatest area for desaturations and re-saturations. Sleep stage effected re-saturation parameters more than desaturation parameters, with a relative difference from NREM 1/2 to REM in duration of 16.7% and 29.8%, in rate of 0.2% and 4.5% and in area of 36.1% and 48.0% for desaturation and re-saturation, respectively, among healthy participants. Similarly, the effect of comorbidities was greater upon re-saturations than desaturations, as participants with heart failure recorded a relative difference to healthy participants of 10.3% and 24.4% for desaturation and re-saturation duration, respectively, 12.8% and 15.0% for rate and 6.4% and 16.4% for area. Sleep stages and comorbidities have significant effects upon nocturnal oxygen re-saturation parameters. Cardiorespiratory comorbidities elicit greater degradations in oxygen re-saturations than they do desaturations.