Tobacco and Public Health - TCSC Indonesia

582
CHRONIC OBSTRUCTIVE PULMONARY DISEASE
This excess decline in lung function is greater among those who smoke more cigarettes
per day and worsens with increasing duration of smoking (Burrows et al. 1977;
USDHHS 1984).
The relationship between smoking and lung function as measured by FEV 1 at
various ages is presented in Fig. 33.1. When more than 70 per cent of lung function is
lost, it is common for smokers to have symptoms from their ventilatory limitation,
most notably shortness of breath on exertion. Once 90 per cent of lung function has
been lost ventilatory limitation can compromise survival and death from ventilatory
failure becomes an increasingly likely and unavoidable outcome. Among normal individuals
who do not smoke, and who do not have substantive exposure to environmental
tobacco smoke, lung function increases as a child grows and the FEV 1 reaches a
peak between ages 20 and 25 years. Thereafter, it slowly declines. This experience is
presented as a thick solid line in Fig. 33.1. Children who are exposed to environmental
tobacco smoke have a lower rate of lung growth. That effect of environmental tobacco
smoke exposure is portrayed by the dotted line prior to age 20 in the figure. This lower
100
80
60
40
20
0
Disability
Death
Smokers
with COPD
All
smokers
Nonsmoker
Quit at
age 40
Quit with onset
of disability
0 10 20 30 40 50 60 70 80 90
Modified from Speizer and Tager 1979
AGE
Fig. 33.1 FEV1 as a per cent of the value at age 25 for smokers, nonsmokers, and those who
quit. The values presented are the FEV1 as a percentage of the value for an individual at age
25 years. The heavy solid line represents those who have never smoked, the dashed line represents
the entire population of smokers including those exposed to environmental tobacco
smoke as children, the thin solid line represents those smokers who are going to develop
COPD, thin solid lines also represent those who quit at age 40 years and when symptoms
develop. See text for description.