Estimating population prevalence of potential airflow obstruction using different spirometric criteria: a pooled cross-sectional analysis of persons aged 40–95 years in England and Wales

Publication type

Journal Article

Published in

BMJ Open

Authors

Shaun Scholes, Alison Moody and Jennifer S. Mindell

Publication date

Summary

Objectives
Consistent estimation of the burden of chronic obstructive pulmonary
disease (COPD) has been hindered by differences in methods,
including different spirometric
cut-offs for impaired lung function. The impact of different definitions
on the prevalence
of potential airflow obstruction,
and its associations with key risk factors, is evaluated using
cross-sectional data from
two nationally representative
population surveys.

Design
Pooled cross-sectional analysis of Wave 2 of the UK Household
Longitudinal Survey and the Health Survey for England 2010,
including 7879 participants, aged
40–95 years, who lived in England and Wales, without diagnosed asthma
and with good-quality
spirometry data. Potential airflow
obstruction was defined using self-reported physician-diagnosed COPD; a
fixed threshold
(FT) forced expiratory volume in
1 s/forced vital capacity (FEV1/FVC) ratio <0.7 and an
age-specific, sex-specific, height-specific and ethnic-specific lower
limit of normal (LLN). Standardised
questions elicited self-reported
information on demography, smoking history, ethnicity, occupation,
respiratory symptoms and
cardiovascular disease.

Results
Consistent across definitions, participants classed with obstructed
airflow were more likely to be older, currently smoke,
have higher pack-years of smoking
and be engaged in routine occupations. The prevalence of airflow
obstruction was 2.8% (95%
CI 2.3% to 3.2%), 22.2% (21.2% to
23.2%) and 13.1% (12.2% to 13.9%) according to diagnosed COPD, FT and
LLN, respectively.
The gap in prevalence between FT and
LLN increased in older age groups. Sex differences in the risk of
obstruction, after
adjustment for key risk factors, was
sensitive to the choice of spirometric cut-off, being significantly
higher in men when
using FT, compared with no
significant difference using LLN.

Conclusions
Applying FT or LLN spirometric cut-offs gives a different picture of
the size and distribution of the disease burden. Longitudinal
studies examining differences in
unscheduled hospital admissions and risk of death between FT and LLN may
inform the choice
as to the best way to include
spirometry in assessments of airflow obstruction.

Volume

4

DOI

http://dx.doi.org/10.1136/bmjopen-2014-005685

ISSN

16

Subjects

Medicine and Health

Notes

Open Access article; This is an Open Access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/