Factor · Smoking
Smoking and longevity
Smoking is the most firmly established behavioural influence on how long people live. Long-running cohort studies of smokers and never-smokers show large differences in survival, and they also show that stopping reduces the excess risk, more so the earlier a person stops.
— What the evidence shows
The British Doctors Study followed male doctors for 50 years and found that lifelong smokers died substantially earlier on average than never-smokers, and that stopping at earlier ages recovered much of the difference.
A large United States cohort analysis reached consistent conclusions: continuing smokers lost roughly a decade of life expectancy compared with never-smokers, and quitting before middle age avoided most of that excess risk.
These estimates describe population averages under the conditions and periods studied. They are not guarantees for any individual.
— What changes after stopping?
The distinctive feature of this evidence is that the same cohorts were followed long enough to observe what happened to people who stopped, not only to people who continued.
Cohorts followed for decades
Smokers and never-smokers tracked over 50 years and across countries.
Survival compared
Lifelong smokers died substantially earlier on average than never-smokers.
Stopping observed
Excess risk falls after stopping, and falls further the longer a person has stopped.
Timing matters
Quitting before middle age avoided most of the excess risk in these cohorts.
These are population averages from particular cohorts and periods, not personal predictions, and the exact number of years differs between studies. Nothing here can be converted into years added by one person quitting.
What kind of evidence this is
- Long-running observational cohort studies
- Dose–response observed
- Association with mortality reproduced across countries and decades
- Understood biological mechanisms
The association is large, dose-related, reproduced across countries and decades, and supported by understood biological mechanisms in cancer, cardiovascular and respiratory disease.
These descriptors summarise the study designs and findings in the sources listed on this page. SnapLongevity does not grade, score or rank the evidence.
— What we know
- The association is very large, dose-related, biologically well understood, and reproduced across countries and decades.
- Risk falls after stopping, and falls further the longer a person has stopped.
- The mechanisms — cancer, cardiovascular and respiratory disease — are established, not merely statistical.
In plain English
- Dose–response
- Risk rises as exposure rises, and falls as exposure falls.Why it matters: A clear dose–response pattern is one of the strongest signals that an association is not just a coincidence.
— What remains uncertain
- Published life expectancy differences come from specific cohorts in specific periods, so the exact number of years differs between studies and populations.
- The long-term health effects of newer nicotine products are not yet established with comparable evidence.
Sources
Continue exploring
- What affects longevityAll six factors, and the kinds of evidence behind each one.
- How life expectancy is calculatedWhy published year differences describe populations, not people.
- Can humans actually extend lifespan?Removing a risk is not the same as adding years to a life.
- Cardiorespiratory fitnessAnother factor where the association is unusually steep.
This page is informational and is not medical advice. Personal medical decisions belong with a qualified healthcare professional.