I am looking for understanding better the variables COPD and asthma in the SHHS.
1/ On COPD for say the first visit there is:
variable "copd15": Doctor of Medicine (MD) said participant had chronic obstructive pulmonary disease (COPD)?
variable "crbron15": Doctor of Medicine (MD) said participant had chronic bronchitis?
variable "emphys15": Doctor of Medicine (MD) said participant had emphysema?
It is my understanding that emphysema or chronic bronchitis are two types of COPD, yet the COPD variable has only n=62 positive test when emphysema has n=132 and chronic bronchitis has n=315. How is it possible?
There are two potentially interesting variables for asthma. My interest is to know if the patient has asthma at the time of the PSG whether SHHS1 or SHHS2. For that purpose I wonder which of these two variables might be the best proxy?
hi201e: e. Do you still have asthma?
asthma15: Doctor of Medicine (MD) said participant had asthma?
3/ On both COPD and asthma
How much time spam between the CPOD/asthma examination and the PSG recording? Is it in the order of days, months, years?
For "asthma15" is it the answer to a questionnaire filled just before SHHS2?
4/ Diagnosis modality
How were COPD and asthma diagnosed? Is it documented somewhere?
What does it mean "Doctor of Medicine (MD) said participant had chronic obstructive pulmonary disease (COPD)?"? Does it relates to a specific test made for diagnosing COPD by the doctor who then reports COPD for the patient?
Thanks Mike, I will try my luck,
Hi Mike (my apology for the mistake),
Thanks for the precision. Do you know who is the contact person(s) from the original studies that I can ask for recovering this information? It would be very valuable to have for our current work this is a variable we can add to SHHS.
A further question on this topic. The "afib" label is meant to represent persistent AF or atrial AFL as per the Minnesota (MN) code 8-3-1 or 8-3-2.
I believe these were extracted from the EMR system and are part of the patient history. My question is, do we know if these patients were treated (and if yes how) for AF/AFL? In other words, I am looking to understand how much these variables are representative of the AF/AFL status at SHHS1.
We will dig more into this given your input. Hopefully, that will be enough
Regarding the AF labels provided in the SHHS variables. There seems to be three options available as part of the SHHS:
1/ AFIB: atrial fibrillation or flutter
Visit 1 and visit 2
Minnesota (MN) code 8-3-1 or 8-3-2. Data derived from standard resting 12-lead electrocardiogram (ECG) with the participant supine. Records were interpreted and Minnesota (MN) codes were provided by clinical cardiologist
2/ AFIB Prevalent
At the first visit
Variable created as part of the analysis for Tung et al. 2017 (PMID: 28668820). Prevalent AF was defined by any of the following: a positive response to the question 'Has a doctor ever told you that you have or had atrial fibrillation'; AF identified on resting 12-lead ECG at the baseline SHHS exam; or if the parent study identified AF documented in the medical record before the SHHS baseline exam.
3/ AFIB incident
After SHHS visit 1
Variable created as part of the analysis for Tung et al. 2017 (PMID: 28668820). Incident AF was considered present if AF was identified on a 12-lead ECG obtained at the second SHHS exam or was adjudicated by the parent cohorts at any time between the baseline PSG and the final follow-up date for AF ascertainment of June 30, 2006.
For variable 2 and 3 the paper from Tung et al. is referenced. For the first variable there is no reference. In addition, there are important differences in the number of cases between the variables. For example in AFIB there are 80 individuals classified as AF during the second visit whereas in AFIBincident there are 332 cases of AF at visit 2.
Do you have some more information/comments/explanation on how to understand the difference between these variables and which one is the most accurate diagnosis of AF during visit 1 and during visit 2?
Thank you Mike. That's clear,
Thanks for the prompt feedback.
Ok so I understand from your response that the ahi_a0h3a follows the rules you defined here (https://sleepdata.org/datasets/shhs/pages/mop/6-627-mop-scoring-respiratory-events.md) but for a 3% desaturation threshold for the hypopneas (adjusted from the computer program to output this variable). Is that correct?
Did you elaborated this variable (ahi_a0h3a) as part of the original SHHS study or was it created at a later date by you/another research group?
Thanks again for your help,
I would like to know how the variable ahi_a0h3a was elaborated from the original scoring guidelines used in defining apneas and hypopneas in the SHHS. Do you have some pointer for me? Do you know of any publication that looked at re-scoring this dataset according to AHI2012 recommended rule and how far the AHI was from ahi_a0h3a?
Definition of ahi_a0h3a: https://sleepdata.org/datasets/shhs/variables/ahi_a0h3a
Definition of the rules used to score apneas and hypopneas: https://sleepdata.org/datasets/shhs/pages/mop/6-627-mop-scoring-respiratory-events.md
In particular the ahi_a0h3a hypopneas take a 3% SpO2 threshold for hypopneas whereas the original scoring guidelines use a 2% threshold.
Some clarification following our exchange.
As it happen the Pleth channel seems to correspond to the PPG signal provided by the oximeter.
My confusion came from the fact that plethysmography is usually called PPG if we are talking about plethysmography measured using an optical sensor and I was also wondering why not two channels of PPG/Pleth were provided (since the oximeter provides PPG at two wavelengths.) What seems to be is that Pleth == PPG but manufacturer usually do not provide the PPG at two the wavelengths to avoid inverse engineering of the calibration used to derive SpO2 from PPGs. So at this stage I understand that Pleth=PPG but it is unclear to me at what wavelength the optical signal is provided and whether this is raw or preprocessed signal. I am checking that with Natus to see if they have more details.