Smoking, cancer, heart disease, and the oral-systemic link: Where we are with research

Dr. Richard Nagelberg examines the links between smoking, lung cancer, and heart disease, as well as the types of research and studies that established the strength of their credibility over time. Likewise, he considers where we are today with the link between oral health and overall health as he evaluates the current state of oral-systemic research.

Perhaps the most universally accepted facts in health care are the detrimental effects of tobacco, particularly cigarette smoking, for nearly every part of the body. It is safe to say that no one disputes the direct causal links between cigarette smoking, lung cancer, and heart disease. Listed below are only two statements regarding the state of this knowledge.

✔️The scientific evidence is incontrovertible: inhaling tobacco smoke, particularly from cigarettes, is deadly. Since the first Surgeon General’s Report in 1964, evidence has linked smoking to diseases of nearly all organs of the body. (surgeongeneral.gov. June 21, 2018)

✔️Smoking is by far the biggest preventable cause of cancer. Thanks to years of research, the links between smoking and cancer are now very clear. Smoking accounts for more than 1 in 4 UK cancer deaths, and 3 in 20 cancer cases. (cancerresearchuk.org)

There is a boatload of research supporting this link. However, there has never been one large-scale double-blinded interventional study demonstrating that smoking causes lung cancer and heart disease. The fact that this link exists is based on the cumulative results of numerous smaller studies over a long period of time.

The reasons are the same for the lack of large-scale interventional studies investigating the link between smoking, lung cancer, and heart disease, among others, as well as that between the mouth and the body. These studies are too costly and full of variables that are difficult to control in a study spanning 20 years or more. It is the cumulative results of research that will demonstrate the strength of the link between oral health and overall health, rather than one definitive piece of research.

While the risks of smoking were being investigated, there were naysayers who doubted the emerging results. In fact, there was substantial skepticism within the medical community about whether the apparent increase in cancer deaths was real or the result of better diagnosis. The study that is credited with the beginning of the stop-smoking movement was published in 1954 by Hammond and Horn. Their paper ended with: "[we are of the opinion that the associations found between regular cigarette smoking and death rates from diseases of the coronary arteries and between regular cigarette smoking and death rates from lung cancer reflect cause and effect relationships.]" (1)

At present, we are in the middle of the oral-systemic research, waiting until a sufficient body of research provides incontrovertible evidence one way or the other.

Reference

1. Hammond EC, Horn D, The relationship between human smoking habits and death rates: a follow-up study of 187,766 men. J Am Med Assoc. 1954;155(15):1316-1328.

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