Question

The study also provided mortality rates for cardiovascular disease among smokers and non-smokers. The following table presents lung cancer mortality data and comparable cardiovascular disease mortality data. Table 2. Mortality rates (per 1,000 person-years), rate ratios, and excess deaths from lung cancer and cardiovascular disease by smoking status, Doll and Hill physician cohort study, Great Britain, 1951-1961. Mortality rate per 1,000 person-years Smokers Non-smokers All Rate ratio Excess deaths Attributable risk per 1,000 person-years smokers 1.23 2.19 percent among 1.30 0.07 Lung cancer Cardiovascular disease 0.9418 8.87 1.3 95% 9.51 7.32 123% 7. Which cause of death has the stronger association with smoking? Why? The following table shows the relationship between smoking and lung cancer mortality in terms of the effects of stopping smoking. Table 3. Number and rate (per 1,000 person-years) of lung cancer deaths for current smokers and ex-smokers by years since quitting, Doll and Hill physician cohort study, Great Britain, 1951-1961 Cigarette smoking status Lung cancer deaths Rate per 1,000 person-years 1.30 Rate ratio 18.5 Current smokers 133 For ex-smokers, years since quitting Less than 5 vears 5-9 years 10-19 years 20+ years Non-smokers 0.67 0,49 0.18 0.19 0.07 9.6 7.0 2.6 2.7 1.0 (referent) 8. Interpret these data. What do these data imply for the practice of public health and preventive medicine? 9. What are the advantages of case-control versus cohort studies? 10. Which type of study would you have done first? Why? Why do the other type of study? 11. Which of the following criteria for causality are met by the evidence presented by this study? Yes No Strong association Consistency among studies Exposure precedes disease Dose-response effect Biologic plausibility

Answer 1

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