Units of measurement for data under MVPA_E5S_T100_ENMO

[tessac...@gmail.com]

Hi,

I am using the GGIR package to decode the raw GENEActive data. 

As I am new to this program and accelerometer, I would like to ask if I am right in understanding that the unit of the data under the columns MVPA_E5S_T100_ENMO and MVPA_E5S_B1M80%_T100_ENMO are in minutes please? I understand that the MVPA threshold unit is in mg though. But am I right to understand that the data under this column in the csv file eg. 

                 MVPA_E5S_T100_ENMO  

mon 120

tue 95

wed 95

thur 15

fri 75

sat 100

are suppose to mean the mins of MVPA spent under the conditions of epoch 5s, with a mvpa threshold of 100 please?

Thank you!!

[Vincent van Hees]

Your interpretation is correct. The improvement of the documentation for the variables that are produced by g.part5 (mode = 5) is on my to do list.

For the moment, please find some clarifications on the abbreviations I used in the variable names:

dur = duration, acc = average acceleration, Nblock = number of blocks

D10 = bout lengths with 10 minutes and longer

T120 = threshold of 120 mg and higher

_pla = plain average across available days

_wei = weighted average across available days where weekend days always weighted 2/5 relative to the contribution of week days

If there is no D like in LIG50_120 then it refers to unbouted time spent between those thresholds

dur_LIGB_D10T50_120 are the time spent in bouts of light activity of at least 10 minutes

WW in filename refers to analyses based on the timewindow from waking to waking up, while MM in filename refers to analyses done on windows between midnight and midnight

SIB=sustained inactivity bouts, are the periods of time during which the arm does not rotate at all for at least 5 or 10 minutes (I do not know what criteria you used). This could be daytime sleep or the monitor not being worn for a very short period of time.

INB are bouts of time during which acceleration is below an acceleration threshold for at least X% of the time.

If you have two bout duration thresholds like 1 and 10 minutes you will get D1T100 and D10T100. In this case D1T100 effectively means bouts between 1 and 9.99 minutes, while D10T100 refers to bouts of at least 10 minutes. 

TMOD and TVIG are total moderate and total vigorous PA with all bouted and unbouted time contributing. Just MOD and VIG are only the unbouted time spent in those categories.

nightwak = night waking time

SIB= sustained inactivity bouts, can be part of inactivity bouts (INB variables), SIB are the sustained inactivity bouts that are not part of the inactivity bouts. This is why I have a TSIB and a SIB variable, explanation of these are:

TSIB = total of all sustained inactivity bouts (regardless of whether they contributed or not to inactivity bouts (INB).

TOIN = Total other inactivity

TIN = Total inactivity = TOIN + SIB = Total other inactivty + Sustained inactivity

So, basically there are the following levels from least active to most active:

- Sleep or SIB

- Other inactivity

- Light

- Moderate

- Vigorous

Additionally they a grouped in:

- MVPA bouts (Moderate or Vigorous)

- Light bouts (just light)

- Inactivity bouts (Other inactivity or SIB)

- And the non-bouted time spent in each of the five categories

And also as the total of each category: TSIB, TOIN, TLIG, TMOD, TVIG

dur_day_min_pla, dur_night_min_pla, and dur_nightandday_min_pla: duration of a day and night time

The bout criteria for inactivity is 0.9, why is this different to the criteria for light and MVPA which is 0.8? Ssomewhat arbitrary decision, but the idea was that if you allow for bouts of 30 minutes it would not make sense if you allow for breaks of 20% of the time(6 minutes !) this is why I used a more stringent criteria for the highest category

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[dominika]

Dear Vincent,

Could you clarify that TLIG, TMOD, TVIG, TIN, TOIN and TSIB refer to the waking time period?

1.      In the Vignette under Special note to p5 output, it is specified that “The duration of all dur_ variables that have _total_ in their name should add up to the length of the full day.”

What is your definition of a “full day”? Do you mean the entire midnight to midnight (or wake-up time to wake-up time) period or waking time only?

The description seems to suggest the former (i.e., that those totals are calculated over the entire MM or WW period) while looking at my data the sum of the time spent in variables prefixed with a total (TVIG etc.) adds up to ‘dur_wakinghours_min_wei’ not to ‘dur_fulldaywindow_min_wei’

I computed the sum of totals as

dur_TOINday_min_wei + dur_TLIGday_min_wei + dur_TMODday_min_wei + dur_TVIGday_min_wei + dur_TSIBday_min_wei

Thank you in advance,

Dominika

[Vincent van Hees]

I think you are right, these add up to waking hours.

Note that T variables do not exist anymore since GGIR version 2.0, they have been replaced by variable names with "_total_" in them. Variable TSIB was omitted in version 2.0. I will add this as an action point for updating the documentation.

Thanks,

Vincent

Dr. Vincent van Hees

Independent consultant

https://accelting.com/

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