Module: Epidemiology and Statistics

Topic 7


Topic 7: How do we know that smoking causes lung cancer?

Objectives

When you have completed the reading and participated in the taught components for this week, we hope you will be able to

  • Explain the role of prospective and historical cohort studies in investigating the causes of disease
  • Identify the main limitations and strengths of cohort studies
  • Understand how absolute and relative risks are derived and what is meant by attributable risk and population attributable fraction
  • Summarise criteria used to infer causality in observational studies and how genetic epidemiology can be used to strengthen causal inference

Lecture

This lecture will describe how cohort studies have been used to study the aetiology of various diseases, their advantages over case-control studies for inferring causality, and their limitations. The talk will discuss the different ways that risk can be measured, with implications for interpretation of study findings. The lecture will conclude with criteria which can be used to decide whether an association between an exposure and a disease outcome is likely to be causal, and how genetic epidemiology can provide further evidence in this regard. 

 

Seminar

In this seminar you will discuss two studies, with questions and answers related to data from two seminal epidemiological studies: the first is a case-control study of risk factors for cot death by Fleming et al (set reading Week 6); the second is Doll’s cohort study of the relation between smoking and mortality (set reading Week 7). The aim of the session is to reinforce what the students have learned in last week’s lecture on case-control studies, and in this week’s lecture on cohort studies.

Preparation for this week

Read the BMJ paper by Fleming et al on cot death (set reading week 6) and the BMJ paper by Doll on smoking and mortality, as well as the personal perspective on his discovery of the link between smoking and lung cancer (set reading week 7).

Before the seminar, please make sure you print and read these questions as they will form the basis of the session.

For a broader perspective on risk from an expert statistician specialising in the Public Understanding of Risk, David Spiegelhalter’s video is worth watching:

You may also want to browse his website: http://understandinguncertainty.org/.

Set Reading

BOOK CHAPTERS

ACADEMIC PAPERS

  • Doll R, Peto R. Mortality in relation to smoking: 20 years’ observations on male British doctors. BMJ 1976; 2: 1525-36. (Read it here)
  • Doll R. How it really happened. Smoking and lung cancer. Am J Respir Crit Care Med 2000; 162: 4-6. (Read it here)

Additional reading

  • Cohort studies (chapter 7) in: Epidemiology in Medicine. CH Hennekens and JE Buring. Ed: SL Mayrent. Little, Brown and Co, Boston.
  • Schulz KF, Grimes DA. Cohort studies: marching towards outcomes. Lancet 2002; 359: 341-5. (Read it here)
  • Doll R et al. Mortality in relation to smoking; 40 years’ observations on male British doctors. BMJ 1994; 309: 901-11. (Read it here)
  • White C. Research on smoking and lung cancer: A landmark in the history of chronic disease epidemiology. The Yale Journal of Biology and Medicine 1990; 63: 29-46. (Read it here)

Videos

Lecture Notes and Powerpoints