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Hypnograms

Commands to show and summarize elements of sleep macro architecture

These commands require staging information to be present in an annotation file.

Command Description
STAGE Output sleep stages per epoch
HYPNO Sleep macro-architecture summaries

STAGE

Export sleep stage information

This command simply writes sleep stage information (e.g. as encoded by an NSRR XML annotation file) to a database. Internally, it creates a single annotation class called SleepStage, with instances that correspond to wake, N1, N2, N3, REM, ? and L (Lights On). The HYPNO command does the same but additionally computes a large number of other statistics. Unlike HYPNO however, the STAGES command can be run after epochs have been masked out. In contrast, HYPNO requires the original, entire EDF, in order to produce meaningful summary statistics on sleep macro architecture.

Warning

Currently, Luna and this documentation uses a not-always-clearcut mixture of sleep stage terminology, e.g. using N2 and NREM2 interchangeably. Also, if stage NREM4 sleep is present, it is summarized explicitly.

Parameters
Parameter Example Description
wake wake=W Set the annotation class for wake epochs
N1 N1=NREM1 Set the annotaiton class for N1 epochs
N2 N2=NREM2 Set the annotaiton class for N2 epochs
N3 N3=NREM3 Set the annotaiton class for N3 epochs
REM REM=REM Set the annotaiton class for REM epochs
? ?=UNKNOWN Set the annotation class for unscored/unknown epochs
Output
Variable Description
CLOCK_TIME Clock time (hh:mm:ss)
MINS Elapsed time from start of EDF (minutes)
STAGE Sleep stage (text value)
STAGE_N Numeric encoding of sleep stage

Numeric stage encoding: The STAGE_N encoding is designed to help with quickly plotting a hypnogram: wake is 1, NREM1, NREM2 and NREM3 are -1, -2 and -3 respectively; REM is 0; unknown is 2. As such, something like the following R command can produce a hypnogram-like representation of the night:

plot( d$E , d$STAGE_N ) 
See also

The lstages() function in lunaR provides a quick way to run the STAGE command for a single EDF, returning just a vector of stage names.

HYPNO

Estimates multiple summary statistics based on the hypnogram

As STAGE does, this command expects manual sleep stages to be present as an annotation. HYPNO produces individual-level summary statistics (e.g. total sleep time, percent in each sleep stage, etc) and epoch-level output (e.g. cumulative elapsed sleep duration, etc). In addition, NREM sleep cycles are calculated based on a modified heuristic following Feinberg and Floyd.

Some definitions: If Lights off and Lights on times can be calculated from the annotations, they are used to calculate sleep efficiency (SLP_EFF), i.e. as total sleep time divided by the total recording time, where the latter is the duration between lights off and lights on. Any epoch with the stage annotation L means that lights are on, i.e. wake but not part of the recording. However, many NSRR annotation files do not have explicit information on when lights off/on events occurred. In this case, Luna assumes that lights off corresponds to the start of the EDF, and lights on corresponds to the end. This may not be appropriate, however, e.g. if the recording continued for a long time after the subject woke (as an example, see the first individual in the tutorial dataset). Luna therefore also provides a second estimate of sleep efficiency, as total sleep time divided by the time from first sleep epoch to final sleep epoch (SLP_EFF2). Overall, if lights on/off annotations are not clearly marked, SLP_EFF2 is likely to be the most robust metric of sleep efficiency. Sleep maintenance efficiency (SLP_MAIN_EFF) is similar to SLP_EFF but the denominator is total recording time minus sleep latency (i.e. from first sleep epoch to lights on/end of recording). Persistent sleep is defined as sleep that follows at least ten minutes of uninterrupted sleep.

Parameters
Parameter Example Description
file file=hypno.txt Optionally, read stage information from a file
wake wake=W Set the annotation class for wake epochs
N1 N1=NREM1 Set the annotaiton class for N1 epochs
N2 N2=NREM2 Set the annotaiton class for N2 epochs
N3 N3=NREM3 Set the annotaiton class for N3 epochs
REM REM=REM Set the annotaiton class for REM epochs
? ?=UNKNOWN Set the annotation class for unscored/unknown epochs
Output

Individual-level summary statistics (strata: none)

Variable Description
TST Total sleep time
TPST Total persistent sleep time
TIB Time in bed
TWT Total wake time
WASO Wake after sleep onset
LIGHTS_OFF Lights off time (hours since midnight)
SLEEP_ONSET Sleep onset time (hours since midnight)
SLEEP_MIDPOINT Sleep midpoint time (hours since midnight)
LIGHTS_ON Lights on time (hours since midnight)
FINAL_WAKE Final wake time (hours since midnight)
SLP_EFF Sleep efficiency (see note above)
SLP_EFF2 Alternate sleep efficiency (see note above)
SLP_MAIN_EFF Sleep maintenance efficiency (see note above)
SLP_LAT Sleep latency (minutes from lights off)
PER_SLP_LAT Persistent sleep latency (mins from lights off)
REM_LAT REM latency (minutes from onset of sleep)
MINS_N1 Total duration of N1 sleep (mins)
MINS_N2 Total duration of N2 sleep (mins)
MINS_N3 Total duration of N3 sleep (mins)
MINS_N4 Total duration of N4 (NREM4) sleep (mins)
MINS_REM Total duration of REM sleep (mins)
PCT_N1 Proportion N1 of total sleep time
PCT_N2 Proportion N2 of total sleep time
PCT_N3 Proportion N3 of total sleep time
PCT_N4 Proportion N4 (NREM4) of total sleep time
PCT_REM Proportion REM of total sleep time
NREMC Number of sleep cycles
NREMC_MINS Mean duration of each sleep cycle

Epoch-level output (strata: E)

Variable Description
CLOCK_HOURS Start time of epoch (hours since midnight)
CLOCK_TIME Start time of epoch (hh:mm:ss)
MINS Start time of epoch (minutes since start of EDF)
STAGE Text description of sleep stage
STAGE_N Numeric encoding of sleep stage (see STAGE example, above)
PERSISTENT_SLEEP Flag to indicate persistent sleep (more than 10 minutes of sleep has elapsed)
WASO Flag to indicate wake after sleep onset
E_N1 Cumulative elapsed N1 sleep (minutes)
E_N2 Cumulative elapsed N2 sleep (minutes)
E_N3 Cumulative elapsed N3 sleep (minutes)
E_REM Cumulative elapsed REM (minutes)
E_SLEEP Cumulative elapsed sleep (minutes)
E_WAKE Cumulative elapsed wake (minutes)
E_WASO Cumulative elapsed WASO (minutes)
PCT_E_N1 Cumulative elapsed N1 as proportion of total N1 sleep
PCT_E_N2 Cumulative elapsed N2 as proportion of total N2 sleep
PCT_E_N3 Cumulative elapsed N3 as proportion of total N3 sleep
PCT_E_REM Cumulative elapsed REM as proportion of total REM sleep
PCT_E_SLEEP Cumulative elapsed sleep as proportion of total sleep
FLANKING_SIM The number minimum number of similarly-staged epochs going either forwards or backwards
N2_WGT Score to indicate ascending versus descending N2 sleep (see below)
NEAREST_WAKE Number of epochs (forward or backwards) since nearest wake epoch (see below)
NREM2REM Number of epochs from this N2 epoch to the N2/REM transition (see below)
NREM2REM_TOTAL Total number of contiguous N2 epochs until a REM transition (see below)
NREM2WAKE Number of epochs from this N2 epoch to the N2/Wake transition (see below)
NREM2WAKE_TOTAL Total number of contiguous N2 epochs until a Wake transition (see below)
CYCLE Cycle number, if this epoch is in a sleep cycle
CYCLE_POS_ABS Absolute position of this epoch in the current NREM cycle (mins)
CYCLE_POS_REL Relative position of this epoch in the current NREM cycle (0-1)
PERIOD Cycle period: NREMP or REMP, or missing if not in a cycle

Information on each NREM sleep cycle (strata: C)

Variable Description
NREMC_START First epoch number of this NREM cycle
NREMC_MINS Total duration of this cycle (mins)
NREMC_NREM_MINS Duration of NREM in this cycle (mins)
NREMC_REM_MINS Duration of REM in this cycle (mins)
NREMC_OTHER_MINS Minutes of wake and unscored epochs
Example

Here we run HYPNO on nsrr02 from the tutorial data:

luna s.lst nsrr02 -o out.db -s "HYPNO" 

The baseline, individual-level output for HYPNO contains summaries such as total sleep time (TST). Here we use Luna's behead utility to view the output in a more human-readable fashion:

destrat out.db +HYPNO  | behead
                       ID   nsrr02              
               FINAL_WAKE   5.22667             
                LIGHTS_ON   7.26                
               LIGHTS_OUT   21.3017             
                  MINS_N1   5.5                 
                  MINS_N2   199.5               
                  MINS_N3   92.5                
                  MINS_N4   0                   
                 MINS_REM   60                  
                    NREMC   5                   
               NREMC_MINS   77.1                
                   PCT_N1   0.0153846153846154  
                   PCT_N2   0.558041958041958   
                   PCT_N3   0.258741258741259   
                   PCT_N4   0                   
                  PCT_REM   0.167832167832168   
              PER_SLP_LAT   63                  
                  REM_LAT   43.5                
           SLEEP_MIDPOINT   1.64333             
              SLEEP_ONSET   22.06               
                  SLP_EFF   59.7826086956522    
                 SLP_EFF2   83.1395348837209    
                  SLP_LAT   45.5                
             SLP_MAIN_EFF   64.7058823529412    
                      TIB   597.5               
                     TPST   231                 
                      TST   357.5               
                      TWT   240                 
                     WASO   72.5                

As indicated above, this individual had five sleep cycles (NREMC). We can view details about each cycle by querying the C stratum of out.db:

destrat  out.db +HYPNO -r C
ID      C  NREMC_MINS NREMC_NREM_MINS NREMC_OTHER_MINS NREMC_REM_MINS NREMC_START
nsrr02  1  72.5       34              12.5             26             92
nsrr02  2  133        118.5           5                9.5            237
nsrr02  3  42         40              2                0              503
nsrr02  4  105.5      72              9                24.5           675
nsrr02  5  32.5       31              1.5              0              887

Finally, we can view epoch-level data (here just a few rows, for a subset of the available variables):

ID       E     CLOCK_TIME  E_SLEEP  STAGE
... skipped ...
nsrr02   89    22:02:06    0        wake
nsrr02   90    22:02:36    0        wake
nsrr02   91    22:03:06    0        wake
nsrr02   92    22:03:36    0        NREM2
nsrr02   93    22:04:06    0.5      NREM2
nsrr02   94    22:04:36    1        wake
nsrr02   95    22:05:06    1        wake
nsrr02   96    22:05:36    1        wake
nsrr02   97    22:06:06    1        wake
nsrr02   98    22:06:36    1        NREM2
nsrr02   99    22:07:06    1.5      NREM2
nsrr02   100   22:07:36    2        NREM2
nsrr02   101   22:08:06    2.5      NREM2
nsrr02   102   22:08:36    3        NREM2
nsrr02   103   22:09:06    3.5      wake
nsrr02   104   22:09:36    3.5      wake
nsrr02   105   22:10:06    3.5      wake
nsrr02   106   22:10:36    3.5      wake
... cont'd ...

Time encoding: Several variables use an hours since midnight 24-hour encoding, so that 20.5, for example, means 8:30pm, etc.

Stage nomenclature: We use the newer format of N1, N2, and N3 sleep for variable names, although if NREM4 sleep has been scored it will be reported as NREM (although, for "consistency" the variable name is N4 rather than NREM4).

Ascending and descending N2: Ascending N2 sleep is defined as N2 sleep that follows N3 and precedes N1, Wake or REM. In contrast, descending N2 sleep follows wake, N1 or REM sleep and precedes N3 sleep. The epoch-level N2_WGT variable (which is only defined for N2 sleep) is an index ranging from -1 to +1 to quantify this. Specifically, it is calculated by looking at the first k non-N2 epochs that come before and after that N2 epoch. (By default, k is 10.) N3 epochs are scored +1 if they are prior to this epoch, otherwise -1. Wake, N1 and REM epochs are scored -1 if they come before this epoch, otherwise +1. The final N2_WGT score is the average of these scores. Epochs that are, e.g., less than -0.5 might be called descending, whereas epochs that are greater than +0.5 might be called ascending.

Stage transition metrics: Luna currently has a set of somewhat idiosyncratic and incomplete stage transition metrics, that were implemented for the specific purpose of considering transitions out of N2 sleep into REM or wake. As they stand, they are unlikely to be of use for most users, but are noted here for completeness. In the future we will add more complete epoch-level metrics and individual summaries (i.e. a basic transition matrix). As it stands, for N2 epochs followed by REM, NREM2REM shows the number of N2 epochs until a REM epoch; NREM2REM_TOTAL shows the total number of contiguous N2 epochs up until that point. The N2/wake variables are defined similarly.

 STAGE   NREM2REM   NREM2REM_TOTAL
  ..............
  ... cont'd ...
  ..............
    REM         0                0
  NREM2         5                5
  NREM2         4                5
  NREM2         3                5
  NREM2         2                5
  NREM2         1                5
    REM         0                0
  ..............
  ... cont'd ...
  ..............