Dear all,
I would like to have an apnea-hypopnea index that resembles as good as possible the AASM 2012 rules in order to compare results on the SHHS dataset with other data that was scored according to these rules.
The AASM rules take into account all (central and obstructive) apneas, together with hypopneas that have either a desaturation > 3% OR an arousal.
At first I thought that the index ahi_a0h3a was a good fit. But this index only counts apneas with an arousal. Furthermore, the hypopnea counts only take hypopneas into account that have an arousal AND desaturation, while in the description of the index OR is mentioned.
Do you happen to now if another index is available that better fits the AASM criteria? Or should I create my own index, in that case is there a hypopnea count available which includes hypopneas with either an arousal or desaturation?
Thanks for your help, Margot.
Margot,
Thanks for checking out the resource and for carefully looking through the SHHS variables. We are in the midst of cleaning up many of these variables - the indices themselves (like ahi_a0h3a) and the component variables (from the variable calculation). The calculations and labels are not quite right.
First and foremost, I think ahi_a0h3a is the variable you want, though the calculation should be changed to this:
ahi_a0h3a = 60 * (hremba3 + hroa3 + hnrba3 + hnroa3 + carbp + carop + canbp + canop + oarbp + oarop + oanbp + oanop ) / slpprdp;
We will make that fix in an upcoming dataset release, but you could calculate the variable yourself in the meantime. To address your points directly:
- Yes, the index should count all apneas, not only those with an arousal.
- The hypopnea variables are mislabeled; these counts are including events with a >=3% desaturation OR arousal (e.g. hremba3 is larger than hrembp3)
Hope this helps! Let us know if you have additional questions.
Mike