Relative risk of tobacco smoking
Among all cancer sites reviewed in this study, the total RR for ever smoking was respectively 1.861 and 2.380 in men and women (Table 1). Top three RR among ever smokers’ men was lung cancer (3.061, 2.956-3.170), upper aerodigestive cancer (1.798, 1.698-1.904), kidney and other urinary cancer (1.333, 1.210-1.468) respectively. And among ever smokers’ women were lung cancer (3.870, 3.703-4.045), upper aerodigestive cancer (1.708, 1.536-1.899) and bladder cancer (1.679, 1.416-1.991). The RRs for ever smokers ranged from 1.078 to 3.870 for cancer mortality, except for a few cases where the RR was estimated to be less than one with insignificant p-values (Table 1).
Table 1 Mortality Rate Ratio at Age ≥35 Years, Selected Cancer Causes, Ever Smokers Versus Never Smokers, Tianjin, China, 2010–2019
Smoking-attributable cancer deaths by age and cancer type
Tobacco smoking was responsible for 23,709 (28.87%) cancer deaths among adult men and 8,648 (17.37%) cancer deaths among adult women among 2010 to 2019 in Tianjin, China (Table 2). As expected, lung cancer comprised the greatest proportion of all smoking-related cancer deaths both in men and women. In men, nearly 50% of lung cancer deaths, 27.55% of upper aerodigestive cancer deaths, 10.11% of liver, 8.08% of stomach, 8.36% of pancreas, 13.56% of kidney and 12.35% of bladder cancer deaths were attributable to tobacco smoking. In women, however, ever-smoking-attributable lung cancer deaths were 31.56% of the total lung cancer deaths. 10.59% of upper aerodigestive cancer deaths, 10.11% of liver, 8.08% of stomach, 10.56% of bladder cancer deaths were attributable to tobacco smoking. In women, the ever-smoking attributable death in 2010, 2014 and 2019 was respectively 20.62%, 16.72% and 16.30%, taking on a decreasing change. But could not found a same trend in men, the ever-smoking attributable death was 27.31%, 30.59% and 29.22% in the above three years (Table 2).
Table 2 Number of smoking-attributable cancer deaths and attributable fraction by site, Tianjin, China, 2010–2019
The smoking rate of men in the study remained stable for 10 years (average: 62.39%), while women showed a downward trend (from 35.33% to 27.58%).
The annual number of smoking-attributable cancer deaths among women has remained relatively constant at around 800 each year since the 2010s (Figure 1), despite the population growth and ageing during this time. The number of smoking-attributable cancer deaths in 55-74 year old women decreased by 31.81% and in ≥75 year old increase by 20.77%, between 2010 and 2019 (Table 3). The annual number of smoking-attributable cancer deaths among men has gradual growth from 1822 to 2684 (increase by 47.3%) between 2010 and 2019 (Figure 1 and Table 3). The number of smoking-attributable cancer deaths in 35-54, 55-74, ≥75 years old men increased by 27.40%, 82.31% and 11.56% respectively between 2010 and 2019 (Table 3). The greatest increase in the annual number of smoking attributable cancer deaths was in men 55-74 years of age with a more the one fold increase between 2010 (n=978) and 2019 (n=1786).
Figure 1 Smoking-attributable cancer deaths by age group, males and females, Tianjin, China, 2010-2019
Table 3 Number of smoking-attributable cancer deaths and attributable fraction by age, 2010, 2014, 2019
Sensitivity analysis for the estimation of PAF of tobacco smoking
Sensitivity analysis showed that the PAF estimates were more sensitive to the variation in RR in women than in men when the upper and lower limits of the 95% CI of RR was used, due to the larger uncertainty in the estimation of RRs for women, particularly for stomach and pancreas (Figure 2).
Figure 2 Sensitivity analysis of the PAF for ever-smoking using the lower and upper limits of 95% confidence interval for relative risks