Relationship of tobacco smoking to cause-specific mortality: contemporary estimates from Australia

Background: Tobacco industry activities and reduced smoking prevalence can foster under-appreciation of risks and under-investment in tobacco control. Reliable evidence on contemporary smoking impacts, including cause-specific mortality and attributable deaths, remains critical. Methods: Prospective study of 178,169 cancer- and cardiovascular-disease-free individuals aged ≥ 45 years joining the 45 and Up Study in 2005–2009, with linked questionnaire, hospitalisation, cancer registry and death data to November 2017. Cause-specific mortality hazard ratios (HR) by smoking status, intensity and recency were estimated, adjusted for potential confounding factors. Population attributable fractions were estimated. Results: There were 13,608 deaths during 9.3 years median follow-up (1.68 M person-years); at baseline, 7.9% of participants currently and 33.6% formerly smoked. Mortality was elevated with current versus never smoking for virtually all causes, including chronic lung disease (HR = 36.32, 95%CI = 26.18–50.40), lung cancer (17.85, 14.38–22.17) and oro-pharyngeal cancers (7.86, 4.11–15.02); lower respiratory infection, peripheral vascular disease, oesophageal cancer, liver cancer and cancer of unknown primary (risk 3–5 times as high); and coronary heart disease, cerebrovascular disease and cancers of urinary tract, pancreas, kidney, stomach and prostate (risk at least two-fold); former versus never-smoking demonstrated similar patterns with attenuated risks. Mortality increased with smoking intensity, remaining appreciable for 1–14 cigarettes/day (e.g. lung cancer HR = 13.00, 95%CI = 9.50–17.80). Excess smoking-related mortality was largely avoided with cessation aged < 45 years. In 2019, 24,285 deaths (one-in-every-six deaths, 15.3%), among Australians aged ≥ 45 years, were attributable to tobacco smoking. Conclusions: Smoking continues to cause a substantial proportion of deaths in low-prevalence settings, including Australia, highlighting the importance of accelerated tobacco control.