Global Initiative for Chronic Obstructive Lung Disease - GOLD

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compared to women 3-6 . Gender-related differences in
exposure to risk factors, mostly cigarette smoking,
probably explain this pattern. In developing countries,
some studies report a slightly higher prevalence of COPD
in women than men. This likely reflects exposure to
indoor air pollution from cooking and heating fuels
(greater among women) as well as exposure to tobacco
smoke (greater among men) 7-15 . Recent large populationbased
studies in the US show a different pattern emerging,
with the prevalence of COPD almost equal in men and
women 16,17 . This likely reflects the changing pattern of
exposure to the most important risk factor, tobacco
smoke.
Estimates based on self-report of respiratory symptoms.
COPD prevalence data based on self-report of respiratory
symptoms (chronic cough, sputum production, wheezing,
and shortness of breath) include people at risk for COPD
(Stage 0) as well as those with airflow limitation, and thus
yield maximum prevalence estimates. These studies
reveal sizable variations in the prevalence of respiratory
symptoms depending on smoking status, age,
occupational and environmental exposures, country or
region, and, to a lesser extent, gender and race. The
data also reveal appreciable variations over time, reflecting
important temporal changes in populations' exposure to
risk factors such as smoking, outdoor air pollution, and
occupational exposures.
The third National Health and Nutrition Examination
Survey (NHANES 3) 16 , a large national survey conducted
in the US between 1988 and 1994, included self-report
questions about respiratory symptoms. The prevalence
of respiratory symptoms varied markedly by smoking
status (current>ex>never). Among white males, chronic
cough was reported by 24% of smokers, 4.7% of exsmokers,
and 4.0% of never smokers. The prevalence
of chronic cough among white women was 20.6% in
smokers, 6.5% in ex-smokers, and 5.0% in never smokers.
There was a smaller gradient in the prevalence of chronic
cough by race (white>black). The prevalence of sputum
production was similar to that of chronic cough in these
groups.
Estimates based on the presence of airflow limitation.
People may have respiratory symptoms such as cough
and sputum production for many years before developing
airflow limitation. Thus, COPD prevalence data based on
the presence of airflow limitation provide a more accurate
estimate of the burden of COPD that is, or probably soon
will be, clinically significant. However, the use of different
cut points to define airflow limitation makes comparing
the results of different studies difficult.
In the NHANES 3 study 16 , airflow limitation was defined
as an FEV 1 /FVC < 70%. The prevalence of airflow
limitation was lower than the prevalence of respiratory
symptoms found in the same study, but both sets of data
reinforce the view that smoking is the most important
determinant of COPD prevalence in developed countries.
Among white males, airflow limitation was present in
14.2% of current smokers, 6.9% of ex-smokers, and 3.3%
of never smokers. Among white females, the prevalence
of airflow limitation was 13.6% in smokers, 6.8% in exsmokers,
and 3.1% in never smokers. Airflow limitation
was more common among white smokers than among
black smokers.
Estimates based on physician diagnosis of COPD.
COPD prevalence data based on physician diagnosis
provide information about the prevalence of clinically
significant COPD that is of sufficient severity to prompt a
visit to a physician. Few population-based prevalence
surveys have been published to provide this information,
and available data are often confusing because asthma
and COPD diagnoses are not separated, all age groups
are considered together, or chronic bronchitis and
emphysema are considered separately.
In the UK the General Practice Research Database 18 ,
which is based on 525 practices serving 3.4 million
patients (6.4% of the total population of England and
Wales), provides population-based data on physiciandiagnosed
COPD (Figure 2-1). In 1997, the prevalence
of COPD was 1.7% among men and 1.4% among
women. Between 1990 and 1997, the prevalence
increased by 25% in men and 69% in women. The
prevalence of COPD among men plateaued in the mid-
1990s, but continued to increase among women, reaching
Figure 2-1. Prevalence (%) of Physician-Diagnosed
COPD in the UK From 1990 to 1997 by Sex 18
2.0
1.5
1.0
0.5
0.0
1990
1991
1992
Men
1993
1994
1995
1996
Women
1997
Reprinted with permission from Soriano JR, Maier WC, Egger R, Visick G, Thakrar B, Sykes J,
et al. Thorax 2000; 55:789-94. Copyright 2000 BMJ Publishing Group.
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