Trends in lung cancer and smoking. 93/1
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Trends in mortality
Figure 1:Lung cancer in Great Britain
Lung cancer has emerged as a major cause of death this century
(figure 1). Some of the increase in the early part of the century
is due to improved diagnosis.
Figure 2:Male mortality from
lung cancer by age and year of death
In the 1940s and 50s lung cancer was the most rapidly increasing
cause of cancer mortality in men. This trend reversed in the 1960s
and 70s, and mortality rates are now declining in men in all age
groups. Nevertheless, lung cancer remains the commonest cause
of cancer mortality in men.
Figure 3:Female mortality
from lung cancer by age and year of death
Over the last 50 years, lung cancer mortality has risen 9-fold
in women. Mortality rates have recently begun to decline in younger
women, but rates continue to increase in older women. Lung cancer
remains the most rapid cause of cancer mortality in women.
Trends in smoking
This substantial increase in lung cancer is attributable to the
widespread uptake of cigarette smoking this century. Smoking was
uncommon at the beginning of the century, but at the end of the
Second World War, more than 80% of men and 40% of women smoked.
The proportion of men who smoke has declined steadily since the
late 1940s. In women, the prevalence of smoking declined in the
1950s, but rose again to a plateau of 40-45% in the 1960s and
70s. Smoking has declined in both sexes since then and 31% of
men and 29% of women currently smoke cigarettes. However, there
is considerable regional variation in smoking within the UK with
the highest levels found in Scotland and the North of England.
Current vs. past history of smoking
The risk of lung cancer depends most strongly on the duration
of smoking, but also on the amount smoked daily and the tar yield
of the cigarette smoked. Given that patterns of smoking have varied
from generation to generation and that smoking became common in
men some 25 years earlier than in women, a person's smoking history
and hence current risk of lung cancer is strongly influenced by
their age, sex and year of birth.
Figure 4:Male cumulative constant tar
cigarette consumption (CCTCC) by age and central year of birth
Figure 5:Female cumulative constant
tar cigarette consumption (CCTCC) by age and central year of birth
The changing patterns of lifetime tar exposure from cigarettes
in successive birth cohorts (i.e. those born in a particular 5-year
period) are shown in figures 4 and 5. The cumulative tar consumption
by a given age for each cohort appears vertically above the cohort's
year of birth. In males, peak lifetime tar consumption at any
given age occurs in those born between 1900 and 1920. In women,
the generation born in 1920s, which has yet to reach old age,
appears likely to have higher lifetime levels of tar consumption
than any previous or subsequent cohort.
Figure 6:Male mortality from
lung cancer by age and central year of birth
Figure 7:Female mortality
from lung cancer by age and central year of birth
These figures show the mortality rate from lung cancer each year
for successive birth cohorts (that is, those born in a particular
5-year period). In males the peak mortality at any given age occurs
in those around 1900. In females the peak mortality occurs in
those born in the 1920s suggesting that lung cancer mortality
may continue to rise in older women for some years.
Summary
-
Current trends in lung cancer reflect the smoking histories
of those alive today, and future trends will have been in
part already determined by past smoking patterns.
-
Lung cancer mortality rates are now declining in men and
younger women, but are likely to rise until at least the turn
of the century in older women.
Footnote
Data presented in figures 4 and 5 are from P.N.
Lee et al, Thorax 1990, 45:657-665, amended to account for
errors noted subsequent to publication and updates to 1990.
The cumulative constant tar cigarette consumption (CCTCC) estimates
are based on survey data relating to manufactured cigarette consumption
per adult, by age, from 1946 onwards, extrapolated back and adjusted
for recent reductions in tar yield.
Because aggregated data for 5-year periods have been used to
derive figures 4-7, each cohort relates to people born over a
10-year period. For example, those aged 55-59 in 1961-65 would
have been born between 1901 and 1910: the central year of birth
for this cohort is 1906.
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