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The EDF and XML annotation files from the nuMoM2b sleep substudy were imported in Matlab for analysis of baseline SpO2 (oxygen saturation). First step involved identification of the initial sleep onset (stage=2). Sixty seconds of wake data preceding the initial sleep onset was identified as the baseline segment for calculation of average SpO2. If 60s of wake data was not present, 30s was used as the baseline segment. Average value of SpO2 signal was calculated at this baseline segment. If there was no usable SpO2 signal or baseline wake data before sleep onset, then baseline SpO2 is missing. A few subjects had less than 90% SpO2 at baseline either due to signal distortion/artifacts or baseline desaturation events and were marked as missing.

Sleep duration is the interval between sleep onset time and lights on/out-bed time while asleep (i.e. total sleep time, TST), while in-bed period is the interval between lights off/in-bed time and lights on/out-bed time (i.e. time in bed, TIB). [(Total Sleep Time (TST)) / (time from sleep onset to morning waking)] * 100 (data can be inaccurate if scorer has not set sleep onset rule properly in compumedics software)

Sleep onset time is the start time of main sleep. This variable measures the within subject variability of sleep onset time.

Sleep onset time is the start time of main sleep. This variable measures the within subject variability of sleep onset time.

Sleep onset time is the start time of main sleep. This variable measures the within subject variability of sleep onset time.

Sleep onset time is the start time of main sleep. This variable measures the within subject variability of sleep onset time.

Sleep onset time is the start time of main sleep. This variable measures the within subject variability of sleep onset time.

Control when :rls_sleep_onset: = 1, 2, or 3 and :rls_disturbed_sleep: = 1 or 2; Probable when :rls_sleep_onset: = 4 or 5 and :rls_disturbed_sleep: = 3; Definite when :rls_sleep_onset: = 4 or 5 and :rls_disturbed_sleep: = 4 or 5; Possible when any other combination

The Apnea Propensity Index (API) is a novel measure of breathing variability based on the abdominal effort channel and optimized around the first sleep onset.

The Apnea Propensity Index (API) is a novel measure of breathing variability based on the abdominal effort channel and optimized around the first sleep onset.

Total sleep period = total estimated sleep duration + wake after sleep onset

Sleep maintenance efficiency is the ratio between sleep duration (i.e. total sleep time, tst) and sleep period in main sleep. Sleep duration is the interval between sleep onset time and sleep offset time while asleep, while sleep period is the interval between sleep onset time and sleep offset time. This variable is similar to variable sawa34; however, sawa34 is derived from Actiware variable sawa24 before data optimization.

Sleep maintenance efficiency is the ratio between sleep duration (i.e. total sleep time, tst) and sleep period in main sleep. Sleep duration is the interval between sleep onset time and sleep offset time while asleep, while sleep period is the interval between sleep onset time and sleep offset time. This variable is similar to variable sawa34; however, sawa34 is derived from Actiware variable sawa24 before data optimization.

Time to first epoch of REM sleep

Harmonized by the NSRR team. Source: :waso:

Sleep Heart Health Study Visit 2 (SHHS2)- Lights are considered to have been calibrated appropriately if, at any time during the study, there is a clear transition (on recorded lights) from lights on to lights off. Otherwise, lights are considered not appropriate (including a light channel showing: no change throughout the study, reversed calibration and/or constant fluctuation from on to off throughout the study.) On studies with clear, but multiple, light transitions "lights off" will be marked at the first "off" transition that is maintained for at least 30 minutes. Light calibration will be considered reliable, but sleep latency will be unreliable. This method will be employed for all studies with the only exception being when onset of sleep occurs prior to the light change, in which "lights off" will be set at the onset of sleep.

Total amount of time spent awake after going to sleep

Harmonized by the NSRR team. Source: :wasoqcpsg:

Total amount of time spent awake after going to sleep [(time in bed) - (sleep latency) - (Total Sleep Time (TST))]

Sleep duration (i.e., total sleep time, TST) is the interval between sleep onset and sleep offset time while asleep. Sleep period is the interval between sleep onset and sleep offset time.