Tobacco smoking and risk for periodontal disease

The magnitude of risk for periodontal disease associated with smoking was investigated by exploring the interrelationships between definition of disease, prevalence and relative risk in a population of dentally aware individuals.

A total of 133 smokers and 242 non-smokers in the age range 20-69 years served as the database. Criteria based on clinical probing of pocket depth and radiographic measurement of bone height were used for the purpose of disease definition. Various pocket frequency cutoff points for two probing depth levels, > or =5 and > or =6 mm, and, in addition, the 30th, 25th, and 20th percentiles of the bone height distribution were alternately selected as criteria.

Disease definition had an impact on the prevalence, and the relative risk varied as a function of the prevalence. For a broad definition of disease such as 1% of pockets > or =5 mm, the prevalence for smokers was approximately twice the prevalence for non-smokers and the odds ratio (OR) was 3.0. A narrower definition such as 15% of pockets > or =5 mm resulted in decreased prevalences for both smokers and non-smokers and an OR of 12.1. Increasing exposures correlated with greater magnitudes of risk. Heavy exposure was associated with greater risk than light exposure. For the combination of a narrow disease definition and heavy exposure, the relative risk was considerable (OR 9.8-20.3).

Smoking-associated relative risk is dependent on definition of disease and prevalence. Given other factors, a narrow definition will result in a low prevalence and a high risk and, vice versa, for a broader definition, prevalence will be high and the risk moderate.