Evidence map›Paper›PMID 36669663›Full record

Trial reportThe Science of the total environment2023

Principal stratification analysis to determine health benefit of indoor air pollution reduction in a randomized environmental intervention in COPD: Results from the CLEAN AIR study.

Han Woo, Kirsten Koehler, Nirupama Putcha, Wendy Lorizio, Meredith McCormack, Roger Peng, Nadia N Hansel

Registry-linked trialOpen access · hybridAbstract readRandomized Controlled Trial
PubMed Full text at PMC Publisher
In one paragraph

Trial report in The Science of the total environment, 2023. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to trial NCT02236858 (Clinical Trial of Air Cleaners to Improve Indoor Air Quality and COPD Health), which is not on this map. Cited by 8 papers.

0numbers the graph read from it
0cells of the map it votes in
8citing papers in PubMed
2.5field-weighted citation impact, top 12% of its field
1 · What the graph read from it

What it found

Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.

The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.

2 · The registry

The trial behind it

Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.

NCT02236858 nacompletednot on this map

Clinical Trial of Air Cleaners to Improve Indoor Air Quality and COPD Health

TypeinterventionalSponsorJohns Hopkins UniversityRan2014 to 2021Enrolled142ConditionsChronic Obstructive Pulmonary Disease (COPD)ArmsHEPA Air Cleaner, Sham HEPA Air Cleaner
3 · Its place in the literature

Who cites it

8 citing papers in PubMed, 16 citations in OpenAlex.

  1. Trial
  2. Review
  3. Health Benefits of Air Purification: A Systematic Review.Environment & health (Washington, D.C.) · 2026
    Review
  4. Article
  5. Article
  6. Article
  7. Article
  8. Article
4 · The record

Corrections and comments

PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.

5 · Who and what money

Authors and funding

7 authors at 2 institutions in 1 country.

Han WooDepartment of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA. Electronic address: hwoo4@jhu.edu.
Kirsten KoehlerDepartment of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
Nirupama PutchaDepartment of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Wendy LorizioDepartment of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
Meredith McCormackDepartment of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
Roger PengDepartment of Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
Nadia N HanselDepartment of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Department of Environmental Health and Engineering, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA.
Johns Hopkins University · USJohns Hopkins Medicine · US

Funding

Clinical trial of air cleaners to improve indoor air quality and COPD healthR01ES022607 · NIEHS · JOHNS HOPKINS UNIVERSITY · PI HANSEL, NADIA N · 2013 to 2017
$3.4M
NIEHS NIH HHS R01 ES022607
6 · The paper itself

Abstract

backgroundIndoor air quality represents a modifiable exposure to Chronic Obstructive Pulmonary Disease (COPD) health. In a randomized controlled trial (CLEAN AIR study), air cleaner assignment had causal effect in improving COPD outcomes. It is unclear, however, what is the treatment effect among those for whom intervention reduced air pollution and whether it was reduction in fine particulate matter (PM

objectiveUsing principal stratification method, we assess indoor pollutants as the intermediate variable, and determine the causal effect of reducing indoor air pollution on COPD health.

methodIn randomized controlled trial, former smokers with COPD received either active or placebo HEPA air cleaners and were followed for 6 months. Saint George's Respiratory Questionnaire (SGRQ) was the primary outcome and secondary measures included SGRQ subscales, COPD assessment test (CAT), dyspnea (mMRC), and breathlessness, cough, and sputum scale (BCSS). Indoor PM

resultsAmong those showing at least 40 % PM

conclusionAir cleaners caused clinically significant improvement in respiratory health for individuals with COPD through reduction in indoor PM

trial registrationClinicalTrials.gov: NCT02236858.

Indexed as

Air PollutantsAir PollutionAir Pollution, IndoorPulmonary Disease, Chronic ObstructiveHumansNitrogen DioxideParticulate MatterAir PollutantsNitrogen DioxideParticulate MatterAir cleanersCOPDEnvironmentParticulate matterPrincipal stratificationRandomized controlled trial

Identifiers

PMID36669663
PMCPMC9975085
OpenAlexW4317214469

What OpenQuestion holds

Textmetadata
LicenceTDM
Read underepoch 390

Registered trials

Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.