Tobacco smoking and all-cause mortality in a large Australian cohort study: findings from a mature epidemic with current low smoking prevalence.
Level 3 - non-randomized controlled study
Prospective cohort study linking survey and registry data
PubMed 25857449 · doi:10.1186/s12916-015-0281-z
What was done
A prospective cohort analysis evaluated 204,953 adults aged 45 years and older from the Australian 45 and Up Study (recruited 2006–2009) linked to hospitalization and mortality records through mid-2012. Participants with a baseline history of cardiovascular disease, stroke, thrombosis, or cancer (other than skin cancer) were excluded. Hazard ratios (reported as relative risks, RRs) for all-cause mortality among current and past smokers compared with never-smokers were adjusted for age, sex, education, income, geographic region, alcohol intake, and body mass index.
What was found
Over 874,120 person-years (mean follow-up: 4.26 years), 5,593 deaths occurred. At baseline, 7.7% were current smokers and 34.1% were past smokers. Compared to never-smokers, the adjusted all-cause mortality RR was 2.96 (95% CI: 2.69–3.25) in current smokers, with similar estimates in men (RR 2.82, 95% CI: 2.49–3.19) and women (RR 3.08, 95% CI: 2.63–3.60). Mortality risks rose with smoking intensity, ranging from an approximate 2-fold increase for ≤14 cigarettes/day to a 4-fold increase for ≥25 cigarettes/day. Risk among past smokers declined with time since cessation, showing no statistically significant excess mortality compared to never-smokers among those who quit before age 45. Current smokers were estimated to die approximately 10 years earlier than non-smokers.
Why it matters
This study provides large-scale, contemporary evidence showing that up to two-thirds of deaths among current smokers in Australia are directly attributable to smoking, while confirming the profound protective effect of early cessation.
Limits
Smoking status was based on baseline self-report and not updated over time. Follow-up was relatively short (mean 4.26 years). Findings are limited to adults aged 45 and older free of major baseline cardiovascular diseases and non-skin cancers, and residual confounding cannot be completely ruled out.
Cited by
- supports Lifelong smokers have a 7 in 10 chance of dying from a smoking-related illness.