A young researcher wanted to do the definitive study on smoking and lung cancer. On his 28th birthday, he received a grant to study adults in the United States and Canada who were between the ages of 45 and 55. He randomly selected 100,000 subjects from census information. All of the subjects were sent questionnaires (and his assistants phoned or visited in person if the subject did not respond). The questionnaire included a number of questions about how much the subject had smoked in their lives. Forty years later, the researcher's large team of assistants searched records to determine cause of the death of the adults in the study. For most of the subjects, the cause of death was listed on the death certificate. For those subjects that had ambiguous causes stated on the death certificate, the assistants searched death notices in newspaper articles, contacted doctors, relatives, hospitals, etc. They could not obtain records for 23 missing persons and 52 of the subjects were still alive. Analysis of the 99,925 records showed that smokers were 42 times more likely to die of lung cancer than non-smokers if they smoked one pack or more of cigarettes a day. The researcher concluded that this study clearly shows that lung cancer is caused by smoking.
Can we say from this study that smoking causes lung cancer? Answer