prevalence of COPD

Estimating and comparing the prevalence of COPD in different
countries is complicated by differences in its precise definition
and in the level of underdiagnosis. For example, in the United
Kingdom mild COPD is defined as the ratio of forced
expiratory volume in 1 second (FEV1) to the forced vital
capacity (FVC) being < 0.7 and the FEV1 being 50-80% of the
expected value. Other guidelines suggest slightly different
spirometric values (see third article in this series).
A national UK study reported an abnormally low FEV1 in
10% of men and 11% of women aged 16-65 years. Similarly, a
study in Manchester found non-reversible airflow obstruction in
11% of adults aged > 45, of whom 65% had not had COPD
diagnosed. In the United States the reported prevalence of
airflow obstruction with an FEV1 < 80% of the expected value is
6.8%, with 1.5% of the population having an FEV1 < 50% of
expected and 0.5% having more severe obstruction (FEV1 < 35%
of expected). As in the UK, about 60% of those with airflow
obstruction had not had COPD diagnosed. As much as 40-50%
of the actual prevalence of COPD, based on measurements of
ventilatory function,may be undiagnosed;many people present
relatively late with moderate or severe airflow obstruction.
In England and Wales some 900 000 people have COPD
diagnosed—so, after allowing for underdiagnosis, the true
number with COPD is likely to be about 1.5 million. The mean
age at diagnosis in the UK is roughly 67 years, and prevalence
increases with age. COPD is more common in men than
women and is associated with socioeconomic deprivation. The
prevalence of diagnosed COPD in women is increasing (from
0.8% in 1990 to 1.4% in 1997), whereas in men it seems to have
reached a plateau since the middle 1990s. Similar trends have
been reported in the US. These trends in prevalence probably
reflect sex differences in cigarette smoking since the 1970s.