The association of dental plaque with cancer mortality in Sweden. A longitudinal study

OBJECTIVES To study whether the amount of dental plaque, which indicates poor oral hygiene and is potential source of oral infections, associates with premature death from cancer. DESIGN Prospective cohort study. PARTICIPANTS 1390 randomly selected healthy young Swedes followed up from 1985 to 2009. All subjects underwent oral clinical examination and answered a questionnaire assessing background variables such as socioeconomic status and smoking. OUTCOME MEASURES Causes of death were recorded from national statistics and classified according to the WHO International Classification of Diseases. Unpaired t test, χ(2) tests and multiple logistic regressions were used. RESULTS Of the 1390 participants, 4.2% had died during the follow-up. Women had died at a mean age of 61.0 (±2.6 SD) years and men at the age of 60.2 (±2.9 SD) years. The amount of dental plaque between those who had died versus survived was statistically significant (p<0.001). In multiple logistic regression analysis, dental plaque appeared to be a significant independent predictor associated with 1.79 times the OR of death (p<0.05). Age increased the risk with an OR of 1.98 (p<0.05) and gender (men) with an OR of 1.91 (p<0.05). The malignancies were more widely scattered in men, while breast cancer was the most frequent cause of death in women. CONCLUSIONS This study hypothesis was confirmed by showing that poor oral hygiene, as reflected in the amount of dental plaque, was associated with increased cancer mortality.