Epigenetic Age among U.S. Adults with Chronic Respiratory Diseases: Results from NHANES 1999-2002

In this study, we examined the association of epigenetic aging clocks and respiratory traits in participants from the National Health and Nutrition Examination Surveys (NHANES) 1999-2000 and 2001-2002 survey cycles. In NHANES, the respiratory phenotypes are defined based on self-reported data from standardized questionnaires regarding respiratory health (and other medical conditions) administered by trained personnel specializing in respiratory health. Questionnaires were administered by trained household interviewers in in-person interviews. We examined all the questions detailed in the NHANES website and used the following ones to define the different phenotypes:

Wheezing

• Respiratory Health and Disease Questionnaire (RDQ) (RDQ.070): In the past 12 months {have you/has SP} had wheezing or whistling in {your/his/her} chest?

Wheezing attacks

The frequency of wheezing attacks in the past year was defined based on the following question and dichotomized for having <12 or ≥12 wheezing attacks:

• RDQ.080: [In the past 12 months], how many attacks of wheezing or whistling {have you/has SP} had?

Asthma ever

• Medical Conditions Questionnaire (MCQ) (MCQ010): Has a doctor or other health professional ever told {you/SP} that {you have/s/he/SP has} asthma?

Current asthma

• MCQ035: {Do you/Does SP} still have asthma?

Asthma exacerbations

Only for individuals with current asthma, asthma exacerbations were defined based on the self-reported declaration of asthma attacks or emergency care visits for asthma in the past year.

• MCQ040: During the past 12 months, {have you/has SP} had an episode of asthma or an asthma attack?
• MCQ050: [During the past 12 months], {have you/has SP} had to visit an emergency room or urgent care center because of asthma?

Emphysema

• MCQ170G: Has a doctor or other health professional ever told {you/SP} that {you/s/he} had emphysema?

Chronic bronchitis

• MCQ170K: Has a doctor or other health professional ever told {you/SP} that {you/s/he} had chronic bronchitis?

Chronic obstructive pulmonary disease (COPD)

Based on the response to the questions about emphysema (MCQ170G) and chronic bronchitis (MCQ170K)

Age of COPD onset

Based on the response to the following two questions about the age when emphysema or chronic bronchitis was diagnosed:

• MCQ180G: How old {were you/was SP} when {you were/s/he was} first told {you/s/he} had emphysema?
• MCQ180K: How old {were you/was SP} when {you were/s/he was} first told {you/s/he} had chronic bronchitis?

Here, we publicly published the summary statistics of all associations tested in this study and the R code.