The 21st century hazards of smoking and benefits of stopping: a prospective study of one million women in the UK.
Level 3 - non-randomized controlled study
Prospective cohort study with national mortality record linkage.
PubMed 23107252 · doi:10.1016/S0140-6736(12)61720-6
What was done
A prospective cohort study recruited 1.3 million UK women between 1996 and 2001, resurveyed them postally at roughly 3 and 8 years, and tracked mortality through national records up to January 1, 2011 (mean follow-up 12 woman-years, SD 2). After excluding 0.1 million women with prior disease, 1,180,652 women (median baseline age 55 years) were analyzed. Cox regression models calculated adjusted relative risks for mortality comparing current and ex-smokers (categorized by cessation age) with never-smokers.
What was found
During follow-up, 6% (66,489/1,180,652) of women died. Baseline smokers had a mortality rate ratio (RR) of 2.76 (95% CI 2.71–2.81) versus never-smokers; those still smoking at the 3-year resurvey had an RR of 2.97 (95% CI 2.88–3.07). Smoking fewer than 10 cigarettes per day had an RR of 1.98 (95% CI 1.91–2.04). Of the 30 most common causes of death, 23 were significantly elevated in smokers (lung cancer RR 21.4, 95% CI 19.7–23.2). For ex-smokers who stopped permanently at ages 25–34 or 35–44, all-cause mortality RRs were 1.05 (95% CI 1.00–1.11) and 1.20 (95% CI 1.14–1.26), respectively, avoiding 97% and 90% of the excess mortality of continuing smokers. Projections indicated 53% of smokers versus 22% of never-smokers die before age 80, representing an 11-year difference in lifespan.
Why it matters
This study provides the first direct evidence on the full lifetime hazards of smoking and benefits of early cessation in women, demonstrating that prolonged smoking hazards are as severe as in men, but cessation before age 40 recovers almost all lost life expectancy.
Limits
Smoking status and age at cessation were determined via self-reported postal questionnaires, introducing potential misclassification and recall bias. The sample was restricted to UK women born around 1940, which may limit generalizability to other populations, men, or cohorts with different lifetime smoking patterns and healthcare environments.
Cited by
- supports Lifelong smokers have a 7 in 10 chance of dying from a smoking-related illness.