Study by Doll et Peto
of tobacco consumption by British physicians


First published in October 1984 (Br Med J 1994, 309, 937-939), this study concerns a group of physicians followed for a period of over 40 years. An update of the study in 2004 has not changed the results presented below.

In 1948, in order to evaluate the potential ravages of smoking, Austin Bradford HILL et Richard DOLL enrolled 35,000 British male physicians to answer a questionnaire about their smoking habits. New questionnaires were sent in 1957, 1966, 1972, 1978 and 1990. Almost forty years after the first questionnaire, 95% of the physicians still alive (around 11,000 doctors) continued to answer them.

The first publication showed that after 20 years, there was a very significant difference in life span between smokers (blue line on the graph) and non smokers (red line on the graph).

First study

Second study

Twenty years later, a tripling of mortality due to tobacco is observed: the life span of smokers remains identical to that previously observed, whereas medical progress has allowed a significant increase in life span (more than 80% of the non-smoking doctors over 70 were alive, around 35% were over 85). The median survival had increased by 3 years.

By grouping these two studies, Doll and Peto demonstrate that life expectancy is conversely proportional to the tobacco consumption.

Life expectancy of the British doctors

What was the cause of death among the smoking doctors?

They are very similar to the causes analysed by a prospective study of the American Cancer Society between 1984 and 1988.

Annual death rate for 100,000 men between 35 and 69 years

Cause

Have never smoked regularly

Regular smoker

Overmortality due to smoking

Cancer

  • Lung,

  • Head & Neck and oesophagus

  • Other cancers



8

5

109



196

28

198



188

23

79

Respiratory diseases

9

62

53

Vascular diseases

176

446

270

Cirrhosis - Suicide - Accidents

39

81

42

TOTAL

382

1.083

701

Their are three times more deaths between the age of 35 and 69 among smokers, compared to non-smokers. Young men are the most affected by smoking.

Optimism

The study by Doll and Peto brings an optimistic point of view: stopping smoking is very profitable and the earlier it happens, the longer life expectancy will be. Thus a prevention policy is very useful.

Usefulness of quitting smoking before 35 years.
(blue: non smokers, red: still smoking, green: quitting doctors)

Usefulness of quitting smoking before 45 years.
(blue: non smokers, red: still smoking, green: quitting doctors)

Usefulness of quitting smoking before 55 years.
(blue: non smokers, red: still smoking, green: quitting doctors)
Usefulness of quitting smoking after 55 years.
(blue: non smokers, red: still smoking, green: quitting doctors)

Up to 45 - 50 years, it is still useful to quit smoking.

These impressive studies by Doll and Peto concerning 35,000 British physicians followed during 40 years, therefore brings major scientific breakthroughs:

All of this data constitutes the most realistic and scientific approach for the prevention of smoking.

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