An "S-shaped" relationship between smoking duration and alveolar bone loss: Generating a hypothesis

Background: A number of epidemiological studies have shown that smoking is a risk factor for periodontal disease. Little is known about the relationsh ip between smoking duration and alveolar bone loss. The purpose of this res earch was to describe the prevalence of alveolar bone loss according to smo king status in Norway. A dose-response model for duration of tobacco smokin g on alveolar bone loss was then developed and discussed. Methods: The study population consisted of 812 individuals living in Norway aged 45 to 64 years old (248 current smokers, 245 former smokers and 319 n on-smokers). Alveolar bone loss was measured on bite-wing radiographs. Simp le descriptive statistics were used to describe the central tendency and va riation in alveolar bone loss. Regression analyses were performed to study the relationship between smoking duration and alveolar bone loss. Results: Mean alveolar bone loss varied between 1.51 mm and 2.64 mm dependi ng on smoking status and age. Mean alveolar bone loss was lowest in non-smo kers and highest in current smokers. Given identical smoking status, the me an alveolar bone loss increased with increasing age except for the 2 oldest age groups of current smokers. Conclusions: Our results generate the hypothesis that the relationship betw een smoking duration and alveolar bone loss was "S-shaped." Assuming that a lveolar bone loss is irreversible after smoking cessation, it could be hypo thesized that there is a threshold period for tobacco smoking after which t he accumulated effect of smoking becomes clinically observable. After a cer tain number of years of smoking, the effect on alveolar bone loss seems to level out. To test this hypothesis, the relationship between smoking durati on and alveolar bone loss should be studied in a prospective study design.