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hazards of smoking and benefits of cessation
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Hazards of smoking and benefits of stopping: UK and worldwide
Richard Peto, University of Oxford
• Many young men started smoking in the first few decades of the 20th century, so full lifelong risks are now known.
• Young women started smoking around mid-century, so hazards in later middle age only just became apparent
Richard Doll: mortality and smoking in male British doctors born 1900-30
34,000 men recruited in 1951 & followed up to 2001
– Moderate hazard for smokers born 1851-1899, as they did not smoke substantial numbers of cigarettes when young
– Bigger hazard for smokers born 1900-1930: about HALF eventually killed by tobacco
– Those who stopped before age 40 (preferably well before 40) avoided nearly all the excess risk in later middle age
THE UK MILLION WOMEN STUDY Valerie Beral, Kirstin Pirie, Richard Peto, unpublished
First large prospective study of women who have smoked throughout adult life
Big risks, even though UK cigarette yields have
been lowered in recent decades
Current vs never-smoker, all-cause mortality ratio*
THE UK MILLION WOMEN STUDY ‘
1.8
2.6
3.4
*Fully standardised mortality ratio, by smoking habit at start of 12-year FU
THE MILLION WOMEN STUDY
All-cause mortality Ex-smokers and current smokers
3.1
2.1
1.7
1.2 1.06
Stopped at age 35-44
Current smokers
Age at starting 18.8 19.0
Cigarettes per day while smoking
14.7 15.3
THE MILLION WOMEN STUDY
THE MILLION WOMEN STUDY
Lung cancer mortality Ex-smokers and current smokers
24.6
13.0
6.4
3.5 1.8 1.5
THE MILLION WOMEN STUDY
All vascular mortality Ex-smokers and current smokers
3.7
2.0
1.8
1.2 1.0
Hospital admission with any mention of
disease/procedure
Current versus never-smoker
Illustration of the effects of a 3-fold difference in annual death rates on mortality at ages 35-79 *
* Taking death rates in smokers to be twice the UK 2009 death rates, and death rates in non-smokers to be two-thirds of these national death rates
78%
47%
Nationwide delay between increase in smoking by young adults
& main increase in tobacco deaths
when they reach middle & old age
eg, USA 1900-2000
Chinese cigarette increase 40 years after US increase
Delayed hazard: observed (1950, 1990) and predicted (2030) proportions of all deaths at ages 35-69 due to tobacco
US (all adults) China (men)
1950 12% 1990 12%
1990 33% 2030 33%
Product of domestic cigarettes in China
0
50
100
150
200
250
1949 1954 1959 1964 1969 1974 1979 1984 1989 1994 1999 2004
Billion
2000 billion
1000 billion
INDIA: 1 million tobacco deaths
per year during the 2010s
Jha et al, NEJM 2008
World tobacco deaths, if current smoking patterns continue
2000-2025 ~150M
2025-2050 ~300M
2050-2100 >500M
TOTAL for the
21st century
~1000M
(1 billion)
Compare with
20th century total
~100M
(0.1 billion)
Prevention of a substantial proportion of the 450 million tobacco deaths before 2050 requires adult cessation
Continuing to reduce the % children starting smoking prevents many deaths,
but its main effect will be on mortality in ~2050 & later
Worldwide, HIV, TOBACCO, ALCOHOL & OBESITY
are the only big causes of death that have increased substantially since 1990 in
some large populations.
Death in old age is inevitable,
but death before old age is not