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Using the sum of events from the XML divided by the total sleep time (SLPPRDP) is the correct way to calculate an AHI. Some issues have crept into the SHHS scoring annotation data over time due to the data's age and bugs when converting with newer versions of the Compumedics software. This can make the XML data difficult to understand at times.
The Known Issues on the Polysomnography Introduction describe some of the problems you might encounter when working with the XMLs. The main issues I can see for your purposes are the oxygen desaturation linking/missingness (as you noted) and the respiratory events scored in wake (which would not count toward the AHI). To identify events scored in wake versus sleep you would need to also merge and align the staging annotations that are listed near the end of the XML files.
I hope this helps!
Thanks for checking out some of the SHHS data.
What do you mean by "the number of all [events in XML file] can not correspond to variable like ahi_a0h3a"?
Generally (in the vast majority of cases), the counts used in the AHI numerator (# of events / total sleep time) should match the count of events in the XML files. SHHS is our oldest data and we have seen some cases of scoring data that may have been corrupted over time. We hope to better document these cases over time.
Another thing to look out for in the SHHS data are respiratory events scored in wake epochs, which would not have counted toward the AHI variable in the dataset.
Fantastic! Thanks again for using the resource and for letting us know about the publication.
It looks like EDFbrowser can export EDF files to ASCII (.txt). http://www.teuniz.net/edfbrowser/
I came across this discussion, which mentioned EDFbrowser: https://www.researchgate.net/post/Is_it_possible_to_convert_EEG_dataset_into_csv_file_and_then_analyse_using_R_tool_or_weka
I tried this out myself in EDFbrowser and it seemed to work pretty well. The EDF is converted into 4 text files - annotations (EDF+ I assume), data (signal values), header, and signals (from EDF header).
I shared your post with other members of the team, which stirred up some interest. I will email you about next steps. Thanks for sharing and good luck with ongoing development!
I asked around and was informed that submitting the article to PMC is not required in this case. As long as you included the NSRR citations (from DAUA and dataset documentation page) then I think you'll be fine.
Please give us a heads-up when the article is out!
A couple years after SHHS Visit 1 there was an Interim Follow-up Call, which has this variable: treatedsleepapnea (based upon "Yes" responses to sleepapnea)
That said, use of CPAP was an exclusion criteria for participants recruited to undergo polysomnography at Visit 2. From the SHHS2 Manual of Procedures:
Congrats!
I'm not sure about the open access question - let me bring it up with other members of the team and get back to you.
Not a stupid question - I agree this information was difficult to find. The CT.gov link provides a fuller description of the three treatment arms.
For the treatmentarm variable, the meanings are as follows:
I will add some clarification to the HeartBEAT documentation. Thanks for bringing this to our attention and let us know if you have further questions!
If RESTAN4 = "1: Yes", this indicates more than 30 minutes of the sleep period had either lost or unscorable EEG data. RESTAN2 and RESTAN3 indicate when the recording either started or ended in sleep.