We used both of the approaches mentioned above to estimate how much reductions in tobacco smoking have contributed to the decrease in mortality rates
from cancer in the United States. We also used a third, related method to consider the impact of smoking reduction on the number of deaths
from cancer. In all analyses, we used lung cancer as a proxy to represent the total impact of cigarette smoking on all cancer mortality. We recognise that active smoking causes many other cancers besides lung cancer, including cancers of the oral cavity, nasal cavity and paranasal sinuses, nasopharynx, oro‐ and hypopharynx, larynx, oesophagus (squamous and adenocarcinoma), pancreas, stomach, liver, kidney, renal pelvis, ureter, urinary bladder, uterine cervix, and acute myeloid leukaemia.2
However, lung cancer deaths comprise the majority (80%) of all smoking‐attributable cancer deaths in the United States,3
and cigarette smoking accounts for a larger fraction of lung cancer deaths in men (88%) and women (72%) than any other smoking‐attributable cancer except laryngeal cancer.3
The trend in mortality from laryngeal cancer is similar to that from lung cancer, but it accounts for only about 1% as many deaths.1,4
Because of the high attributable fraction for lung cancer, the temporal trends in lung cancer mortality are much less influenced by changes in other risk factors or by the consequences of early detection and/or treatment than are other smoking‐attributable cancers.
Our first approach considered only the observed change in death rates from all cancers combined and from lung cancer from 1991 to 2003. As shown in table 1, the overall cancer death rate decreased by 16.1% in men and by 8.4% in women from 1991 to 2003. During the same period, the lung cancer death rate decreased by 20% in men but increased—rather than decreased—by 9.6% in women. Based on the absolute change in the death rates, it can be seen that the decrease in the lung cancer death rate in men accounted for 40% of the decrease in the overall cancer death rate in men. In contrast, none of the decrease in the all cancer death rate in women was accounted for by lung cancer. In fact, the trend in lung cancer was in the opposite direction of the trend in overall cancer death rates in women. The decrease in overall cancer mortality in women would have been larger than it was, had there not been a small increase in lung cancer mortality.
Table 1Overall and lung cancer deaths rates in 1991 and 2003
As mentioned above, the first approach ignores the levelling off of cancer death rates that occurred in men since the mid‐1970s, and in women since 1990. Figure 1 depicts the observed trends in the age‐standardised lung cancer death rate as solid lines for men (red) and women (blue) from 1930 through 2003. As shown, the observed lung cancer death rate (per 100
000) in men increased steeply from 1950–1975, then increased more gradually through 1990, before beginning to decrease. Among women the lung cancer death rate increased most steeply from 1975 to 1990 and then levelled off, but did not decrease through 2003.5
Figure 1Observed and project lung cancer death rates, United States, 1930–2003. The observed death rates, indicated by solid lines, are based on US Mortality Public Use Data Tapes, 1960–2003, and US Mortality Volumes 1930–1959, (more ...)
Our second method was to project what might have happened to cancer mortality rates had there been no reductions in smoking since the 1950s. We assumed that the lung cancer death rate would have continued to rise through 2003 as steeply as it had in the period 1950–1975 for men and 1975–1990 for women. The dotted lines in fig 1 and the predicted values in table 1 indicate what would have happened to lung cancer death rates under this scenario. The predicted lung cancer death rate is higher than the observed rate in both 1991 and 2003 in men and women. Furthermore, the predicted lung cancer death rates would have increased from 1991 to 2003 in both sexes, and the increase would have been sufficiently large to cancel out nearly all of the decrease in overall cancer mortality from 1991 to 2003 (table 1). This scenario, although hypothetical, provides an alternative, and perhaps more realistic view of what the actual benefits of past reductions in smoking have been with respect to cancer mortality.
It may be argued that a straight line projection overestimates the actual increase in lung cancer death rates that would actually have occurred had there been no tobacco control interventions to prevent further increases. This may or may not be true. Certainly the lung cancer death rate in men would have continued to increase beyond its peak of 90.6 per 100 000 in 1990, as was the case in the United Kingdom6
where smoking prevalence was allowed to increase for longer before the introduction of control measures. In these countries the lung cancer death rate in men (standardised to the US 2000 age distribution) peaked at 114.5 in 1977 in England6
and at 120.5 in Hungary in 1995.7
Smoking prevalence in the United Kingdom peaked at 71% and 67% among men aged 25–34 and 35–59 years, respectively in 1948–52.6
In contrast, the prevalence of current cigarette smoking among adult men in the United States decreased after reaching 52.5% in 1966.8