A great deal. Quitting smoking lowers the risk of at least 12 types of cancer, including cancers of the lung, mouth and throat, oesophagus, bladder, stomach and liver [1]. Lung cancer risk starts to fall within the first few years [5], and overall cancer risk drops to half that of people who keep smoking after about 15 years [4]. Quitting before the age of 40 prevents more than 9 in 10 of the early deaths caused by continuing to smoke, and quitting at any age, even after a cancer diagnosis, helps people live longer [1, 2, 3, 6].
Key points
- It is never too late: quitting smoking helps at any age and can add up to 10 years of life [1, 3].
- The sooner, the better: quitting before the age of 40 prevents more than 9 in 10 of the early deaths caused by continuing to smoke [2, 3].
- Cancer risk falls gradually: lung cancer risk falls within the first few years, and overall cancer risk falls clearly after about 10 to 15 years [4, 5].
- Even after a cancer diagnosis: patients who stopped smoking lived longer [6].
- Help raises the chance of success: counselling and medicines such as varenicline or nicotine replacement make quitting more likely [7, 8, 9].
- Former heavy smokers may need a yearly lung CT scan [11].
How does cancer risk fall after quitting?
Smoking raises the risk of at least 12 types of cancer, and quitting lowers the risk of all of them: lung, larynx, mouth and throat, oesophagus, pancreas, bladder, stomach, bowel, liver, cervix, kidney and a type of blood cancer called acute myeloid leukaemia [1].
This drop does not happen overnight; it grows year by year:
- Lung cancer: in a long-running study in the United States, heavy smokers who quit had about two fifths less risk of lung cancer within 5 years of quitting than those who kept smoking [5].
- All cancers: in a study of about 3 million people in South Korea, overall cancer risk fell clearly about 10 years after quitting and, after 15 years, was half that of people who kept smoking. Quitting lowered the risk at every age [4].
- But the risk never falls quite to zero: even 25 years after quitting, former heavy smokers had more than 3 times the lung cancer risk of people who had never smoked [5]. That is why paying attention to symptoms and screening matters.
| Age at quitting | Extra years of life compared with continuing to smoke |
|---|---|
| 25 to 34 years | About 10 years [3] |
| 35 to 44 years | About 9 years [3] |
| 45 to 54 years | About 6 years [3] |
In a study of more than one million women in the UK, quitting before the age of 40 also prevented more than 9 in 10 of the early deaths caused by continuing to smoke [2]. Quitting at older ages helps too [1].
If I have cancer, does quitting smoking still help?
Yes, and it matters a lot. In a review of 36 studies of more than 17,000 cancer patients who smoked, those who quit after their diagnosis lived longer, and their cancer came back or progressed less often [6]. Most of these studies were in lung cancer and head and neck cancers, but the benefit of quitting was similar across different cancers [6].
Tell your care team that you smoke and ask them for help to quit; the best time to stop is now, before or during treatment.
Which methods really help people quit?
Getting help makes success much more likely, especially when counselling and medicines are used together [1, 7]:
- Counselling: face-to-face or telephone sessions with a stop-smoking adviser, and even text-message or online programmes, help people quit [1].
- Nicotine replacement: nicotine patches, gum or lozenges make quitting about one and a half times more likely [9]. Using a patch together with gum or lozenges works better than one type alone [1].
- Varenicline: a prescription tablet that more than doubles the chance of quitting. In studies it worked better than a single type of nicotine replacement [8]. Its most common side effect is nausea [12].
Choose the right method with your doctor, who will take your other conditions and medicines into account.
What about e-cigarettes (vapes) for quitting?
Opinions on e-cigarettes still differ. In the latest review of the studies, nicotine e-cigarettes helped people who wanted to stop smoking slightly more than nicotine replacement did; about 4 more people in every 100 quit smoking [10]. No serious short-term harm was seen in these studies, but the long-term effects are not yet known [10].
The US Preventive Services Task Force does not consider the evidence strong enough to recommend e-cigarettes and advises using proven, safe methods first [7]. If you are thinking about them, talk to your doctor before you start.
I used to smoke. Should I be tested for lung cancer?
If you are 50 to 80 years old, have smoked at least 20 "pack-years" (for example, a pack a day for 20 years) and still smoke or quit within the last 15 years, a yearly low-dose CT scan of the lungs is recommended [11]. This test finds lung cancer earlier and lowers the risk of dying from it [11]. Check whether screening is right for you: Should I be screened for lung cancer?
What should I do? One important step: set a quit date and get help
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Choose your quit date
Pick a date in the near future and tell your family and friends so they can support you.
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Give up hookah and opium too
Hookah is not a safe alternative to cigarettes, and opium also causes cancer; see Does hookah cause cancer? and Does opium cause cancer?
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If you slip, try again
If you slip or do not succeed the first time, do not give up; trying again is recommended [12]. Make a new plan with your doctor.
Frequently asked questions
How many years after quitting does lung cancer risk become the same as a non-smoker's?
I am 60 and have smoked for many years. Is it still worth quitting?
Is cutting down enough?
No. In the study of one million British women, even those who smoked fewer than 10 cigarettes a day died at twice the rate of non-smokers [2]. Cutting down can be a step towards quitting; for people who cannot stop all at once, a doctor can offer a plan to cut down gradually with medicine [12]. The goal is to stop completely.
Is varenicline safe?
Most people tolerate it well. The most common side effect is nausea, which is usually mild; take the tablets after food with a full glass of water [12]. Strange dreams, constipation, wind and vomiting can also occur [12]. If you notice changes in mood, depression or thoughts of harming yourself, stop the medicine and contact your doctor [12].
Does quitting before surgery or chemotherapy help?
Yes. In cancer patients, quitting smoking after diagnosis was linked to longer survival and less cancer recurrence [6]. Talk to your care team about help to quit before treatment starts.
What if I smoke hookah instead of cigarettes?
Hookah is not a safe alternative. See the evidence in Does hookah cause cancer?
Details of the evidence and dosing (for physicians)
For physicians
Mortality and age at quitting. Million Women Study (1.2 million UK women, 12 years): mortality rate ratio 2.76 (2.71 to 2.81) for baseline smokers, 1.98 for fewer than 10 cigarettes a day and 21.4 for lung cancer death. Permanent cessation at 25 to 34 and 35 to 44 years: all-cause mortality RR 1.05 and 1.20, and lung cancer mortality 1.84 and 3.34; stopping before 40 avoids more than 90% and stopping before 30 more than 97% of the excess mortality caused by continued smoking [2]. US NHIS (202,248 people): mortality HR in current smokers 3.0 in women and 2.8 in men; quitting at 25 to 34, 35 to 44 and 45 to 54 years gained about 10, 9 and 6 years of life [3].
Time course of cancer risk. Korean cohort (2,974,820 people, 13.4 years): complete quitters vs continuing smokers, HR 0.83 for all cancers, 0.58 lung, 0.73 liver, 0.86 stomach and 0.80 colorectal; overall risk was slightly higher than in continuing smokers during the first 10 years and fell to 50% of theirs after 15 years or more; lung cancer HR 0.43 when quitting before 50 vs 0.61 after [4]. Framingham (heavy smokers with more than 21.3 pack-years): lung cancer HR vs never-smokers 12.12 at less than 5 years since quitting, 5.88 at 15 to 24 years and 3.85 at 25 years or more; 39.1% lower risk than continuing smokers within 5 years; 40.8% of lung cancers in former smokers occurred more than 15 years after quitting [5].
After diagnosis. Meta-analysis of 36 studies (more than 17,000 patients): cessation at diagnosis was associated with better overall survival (sHR 0.71; 0.65 to 0.78), progression-free survival (0.64) and disease-free/recurrence-free survival (0.59) [6].
Medicines (Cochrane). Varenicline vs placebo RR 2.32 (2.15 to 2.51; high certainty), vs bupropion 1.36 and vs single NRT 1.25; no clear difference vs dual NRT (1.02); cytisine vs placebo 1.30; serious adverse events with varenicline RR 1.23 (1.01 to 1.48), with no clear increase in neuropsychiatric serious adverse events (RR 0.89; low certainty) [8]. Any NRT vs control RR 1.55 (1.49 to 1.61) [9]. USPSTF 2021: behavioural interventions and FDA-approved pharmacotherapy for all non-pregnant adults (grade A) [7].
Varenicline dosing (FDA label). Start one week before the quit date (or quit between days 8 and 35 of treatment): 0.5 mg once daily on days 1 to 3, 0.5 mg twice daily on days 4 to 7, then 1 mg twice daily to complete 12 weeks; a further 12 weeks is recommended for successful quitters. Take after food with a full glass of water. CrCl below 30 mL/min: start at 0.5 mg once daily, maximum 0.5 mg twice daily; haemodialysis: maximum 0.5 mg once daily. Nausea 30% vs 10% on placebo. Monitor for neuropsychiatric symptoms [12].
E-cigarettes. Cochrane 2026 (80 trials, 29,861 participants): nicotine EC vs NRT RR 1.61 (1.23 to 2.12; high certainty), about 4 additional quitters per 100; similar serious adverse events; long-term safety unknown, and only regulated products were studied [10]. The USPSTF 2021 and the 2020 Surgeon General's report judged the evidence insufficient to recommend them [1, 7].
Screening. Annual LDCT for people aged 50 to 80 with ≥20 pack-years who currently smoke or quit within the past 15 years (USPSTF 2021, grade B) [11].
Scientific evidence
Scientific evidence
3 itemsScreening for Lung Cancer
Reduced Lung-Cancer Mortality with Low-Dose Computed Tomographic Screening
Reduced Lung-Cancer Mortality with Volume CT Screening in a Randomized Trial
Related cancer types
References
12 referencesShow all references, 1 with a study cardClose the reference list
Numbers in the text, such as [1], refer to these sources. Sources with a “Study card” button are summarised in the site’s evidence library.
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This page is based on reputable scientific sources and was last updated on 28 October 2026. The content of this website is for educational and informational purposes only and does not replace consultation, diagnosis or treatment by a specialist physician. Consult your treating physician about any treatment decision.
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