How many years until smoking's extra risk of dying fades
In this study it took 35 years or more for all of the extra risk of dying to fade, and most of it faded much sooner. People who had quit 35 years or more earlier, 42 years on average, died at about the same rate as people who never smoked. People who had quit 5 to 14 years earlier still had a 72% higher risk of dying than never-smokers. After 15 to 24 years it was 36% higher, and after 25 to 34 years 18% higher. For people who still smoked it was 180% higher (Thomson, 2022). This was in 551,388 US adults followed for about 11 years. Every number links to its source.
The short version
- The longer ago people had quit, the closer their risk of dying was to that of people who never smoked (Thomson, 2022).
- Counts are for equally large groups at the same current age. Take 14 deaths among people who still smoked. People who had quit 5 to 14 years earlier had between 8 and 9 deaths. After 15 to 24 years it was about 7 deaths, and after 25 to 34 years about 6. After 35 years or more it was about 5, about the same as among people who never smoked (Thomson, 2022).
- Age at quitting showed the same pattern. People who quit before 35 died at about the same rate as people who never smoked. Quitting at 35 to 44 came with a 21% higher risk of dying, at 45 to 54 with 47% higher and at 55 to 64 with 74% higher, against 180% higher for people who still smoked (Thomson, 2022).
- This study watched what people already did, and asked about smoking once. It can't show that quitting caused the lower risk, though the authors say smoking likely explains the gap (Thomson, 2022).
Years since quitting
Each row compares people who had quit that long before the study began with people who never smoked, allowing for age, sex, education, alcohol, and race and ethnicity (Thomson, 2022).
| Time since quitting | Risk of dying, against people who never smoked |
|---|---|
| Still smoking | 180% higher (likely range 173% to 188% higher) (Thomson, 2022) |
| 5 to 14 years (9 on average) | 72% higher (likely range 65% to 79% higher) (Thomson, 2022) |
| 15 to 24 years (19 on average) | 36% higher (likely range 31% to 41% higher) (Thomson, 2022) |
| 25 to 34 years (28 on average) | 18% higher (likely range 14% to 23% higher) (Thomson, 2022) |
| 35 years or more (42 on average) | 4% higher (likely range 0% to 8% higher), about the same (Thomson, 2022) |
The paper doesn't give years since quitting separately for people who quit late. People joined the study at 84 or younger. So everyone who had quit 35 years or more earlier had quit before about 50. People who had quit within 5 years of dying were counted as still smoking. The authors did that because illness can make people quit and also makes dying more likely, which would make quitting look less helpful than it is (Thomson, 2022). The paper gives no separate figure for people who had quit less than 5 years earlier.
The percentages compare risks between groups. They aren't percentage points, and they aren't what any one person would gain by quitting.
Age at quitting
| Age when they quit | Risk of dying, against people who never smoked |
|---|---|
| Before 35 (26 on average) | 3% higher (likely range 1% lower to 7% higher), about the same (Thomson, 2022) |
| 35 to 44 (39 on average) | 21% higher (likely range 17% to 26% higher) (Thomson, 2022) |
| 45 to 54 (49 on average) | 47% higher (likely range 42% to 53% higher) (Thomson, 2022) |
| 55 to 64 (59 on average) | 74% higher (likely range 68% to 80% higher) (Thomson, 2022) |
| Still smoking | 180% higher (likely range 173% to 188% higher) (Thomson, 2022) |
The authors sum it up like this. Quitting before 45 came with about 90% of smoking's extra risk of dying gone, and quitting at 45 to 64 with about 66% of it gone (Thomson, 2022).
The study of 551,388 people
Thomson and colleagues used the US National Health Interview Survey, a yearly survey built to represent the whole country. 551,388 adults aged 25 to 84 answered questions about smoking between 1997 and 2018, and deaths were traced through 2019. "Never smoked" here means fewer than 100 cigarettes in a lifetime. Their average age at the start was 49, and follow-up averaged 11 years. 74,870 of them died, about 14 in 100 (Thomson, 2022).
- People who still smoked died at 2.8 times the rate of people who never smoked. It was 2.7 times for men and 2.9 times for women (Thomson, 2022).
- The gain from quitting was similar in Black, Hispanic and White adults, and in men and women (Thomson, 2022).
Where to start
- Every group of quitters studied, up to those who quit at 55 to 64, had a lower risk of dying than people who still smoked. The paper gives no figures for quitting after 64 (Thomson, 2022).
- Earlier was better. The study can't say what quitting would do for any one person.
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How far to trust these numbers
- This was one follow-up study that watched what people already did. People who quit may differ in other ways from people who still smoke, and the authors say some such differences may remain after their adjustments (Thomson, 2022).
- Smoking was asked about once. Changes after that weren't recorded. Earlier studies suggest some smokers quit later and a few people start, so the authors think both the harm of smoking and the gain from quitting may be underestimated (Thomson, 2022).
- The risk fell step by step with earlier quitting and with more years since quitting. With earlier research, that is why the authors say the extra risk of dying among smokers is likely due to smoking (Thomson, 2022).
- The main results include people who were already ill at the start, who may be more likely both to quit and to die. When the authors left out people with a major long-term illness, the quitters' risk of dying came out closer still to never-smokers' (Thomson, 2022).