Mortality in relation to smoking: 20 years' observations on male British doctors.

TLDR

This study uniquely combined complete 20‑year follow‑up, accurate death certification, and a population that largely reduced cigarette use during the observation period. The authors aimed to determine whether smoking causes excess mortality by examining the relationship between age, tobacco consumption, and various causes of death, and by assessing the impact of quitting smoking. A cohort of 34,440 male British doctors completed a 1951 smoking questionnaire and were followed for 20 years, with all 10,072 deaths and changes in smoking habits meticulously recorded. Smokers had roughly twice the death rate of lifelong non‑smokers under 70 and 1.5‑to‑5‑fold higher rates over 70, with heart disease, lung cancer, COPD, and vascular diseases accounting for most excess deaths; as smoking declined, lung cancer mortality fell relative to other cancers, underscoring a causal link.

Abstract

In 1951 the British Medical Association forwarded to all British doctors a questionnaire about their smoking habits, and 34440 men replied. With few exceptions, all men who replied in 1951 have been followed for 20 years. The certified causes of all 10 072 deaths and subsequent changes in smoking habits were recorded. The ratio of the death rate among cigarette smokers to that among lifelong non-smokers of comparable age was, for men under 70 years, about 2:1, while for men over 70 years it was about 1-5:1. These ratios suggest that between a half and a third of all cigarette smokers will die because of their smoking, if the excess death rates are actually caused by smoking. To investigate whether this is the case, the relation of many different causes of death to age and tobacco consumption were examined, as were the effects of giving up smoking. Smoking caused death chiefly by heart disease among middle-aged men (and, with a less extreme relative risk, among old men,) lung cancer, chronic obstructive lung disease, and various vascular diseases. The distinctive features of this study were the completeness of follow-up, the accuracy of death certification, and the fact that the study population as a whole reduced its cigarette consumption substantially during the period of observation. As a result lung cancer grew relatively less common as the study progressed, but other cancers did not, thus illustrating in an unusual way the causal nature of the association between smoking and lung cancer.