This Article  • Full text  • PDF  • Send to a friend  • Save in My Folder  • Save to citation manager  • Permissions  Citing Articles  • Contact me when this article is cited  Related Content  • Related articles  • Similar articles in JAMA  Topic Collections  • Tobacco  • Pulmonary Diseases, Other  • Oncology  • Lung Cancer  • Alert me on articles by topic

	Since this article does not have an abstract, we have provided the first 150 words of the full text and any section headings.

In Reply: Dr Berger is concerned about the conclusion of our cohort study because it implies a causal relationship between smoking reduction and lung cancer risk. However, I believe the article discusses strengths and limitations of the study given the observational nature, and I do not think we infer more than data allow.

While in general observational studies can only be suggestive of causal relationships, the vast majority of evidence regarding behavioral risk factors for disease, such as smoking, originates from cohort and case-control studies, as it may not be feasible or ethical to conduct randomized trials of risk behavior vs no-risk behavior. This is particularly the case when analyzing modification of risk (harm reduction) such as smoking reduction. This difficulty was demonstrated in 2 randomized trials.^1-2 In the first study,¹ 400 healthy smokers who were unwilling to quit smoking enrolled in a 2-year smoking reduction program, but only 25 . . . [Full Text of this Article]

Nina S. Godtfredsen, MD, PhD
duegodt@dadlnet.dk
Department of Cardiology & Pulmonary Medicine 253
H:S Hvidovre Hospital
Hvidovre, Denmark

RELATED ARTICLES

Smoking Reduction and Lung Cancer Risk
Jeffrey Berger
JAMA. 2006;295(9):1001.
EXTRACT | FULL TEXT  

Effect of Smoking Reduction on Lung Cancer Risk
Nina S. Godtfredsen, Eva Prescott, and Merete Osler
JAMA. 2005;294(12):1505-1510.
ABSTRACT | FULL TEXT