CV risk associated with poor oral health may be modified with better oral hygiene behaviours
Improved oral hygiene care attenuates the cardiovascular risk of oral health disease: a population-based study from Korea
Introduction and methods
Oral health and CV disease have been linked in observational studies [1-3]. Periodontal disease causes transient bacteremia, systemic inflammation and endothelial dysfunctions, which may be the underlying mechanisms in the link with atherogenesis . It is, however, unknown whether the link represents a causal relationship, and it is unknown whether periodontal treatment has a benefit for CV disease [5,6].
Regular tooth brushing, which removes dental deposits below the gingival margin alone, and professional cleaning, which removes mineralized plaques (tartar), are proven to reduce periodontal diseases, dental caries and tooth loss [7,8]. It remains unknown how oral hygiene care interacts with oral health diseases including periodontal diseases in relation to primary CV prevention.
Park et al. therefore set up a population-based study using a large nationwide database to assess the impact of self-reported oral hygiene behavior on the incidence of CV disease. Adults (≥40 years) without a history of CV disease were chosen from the National Health Insurance System-
National Health Screening Cohort (NHIS-HEALS), the only insurance provider in Korea, which covers almost the whole population. The cohort contains data of 514.866 individuals who receive routine (biennial) check-ups between 2002 and 2003, with death records up to the end of 2013. An oral health screening program is provided to participants, which consists of a self-reported survey and oral examination by professional dentists. Data of 247.696 healthy adults were used for this analysis. Median follow-up was 9.5 years, in which 14.893 major CV events occurred (10-year event rate: 6.84%).
- The self-reported questionnaires suggested that about 30% of participants had periodontal disease, 20% at least one dental caries, and 25% had lost one or more teeth.
- Toothbrushing was done at least three times per day by 40.5% of participants, twice by 44.8% and once or less by 14.7%. 25.9% of participants reported dental visits for professional cleaning at least once a year.
- Survivalcurves time free of CV events showed that better oral health behaviors were associated with fewer CV events. The opposite was the case for different oral disease conditions in a dose-dependent manner.
- In multivariable analysis, the effect of periodontal disease on CV events was largely attenuated after adjustment for age and sex (HR: 1.04 instead of HR: 1,17), but the number of missing teeth (HR: 1.12, 95%CI: 1.07-1.16 for 1-7 missing teeth, HR: 1.42 95%CI: 1.22-1.64 for 22-28 missing) and dental caries (HR: 1.10, 95%CI: 1.06-1.15 for 1-5, HR: 1.32, 95%CI: 1.15-1.52 for ≥6) remained statistically significantly associated with CV events.
- Tooth brushing and professional cleaning were still significantly associated with CV events after adjustment. Brushing one more time a day was associated with a 9% lower risk of CV events (HR: 0.91, 95%CI: 0.89-0.93, P<0.001) and regular professional cleaning lowered the risk by 14%, independent of potential confounding factors and oral health problems (HR: 0.86, 95%CI: 0.82-0.90).
- Frequent toothbrushing and regular professional cleaning were associated with better CV outcomes even in those with poor oral conditions. The benefit of tooth brushing was, however, more evident in the absence of periodontal disease and at a low number of dental caries. The benefit of tooth brushing showed no significant interaction with the number of teeth lost. Similarly, the benefit of professional cleaning was consistent in all oral conditions.
This study showed that periodontal disease, an increased number of dental caries and greater tooth loss were associated with a higher risk of CV events. After correction for confounders such as age, hypertension, diabetes and tobacco smoking, periodontal disease was no longer significantly associated with CV disease. Dental caries and tooth loss, both more advanced oral health problems, did remain significantly associated with CV risk. Better oral hygiene on the other hand, such as frequent tooth brushing and regular dental visits, were associated with fewer CV events.
Thus, the data suggest that better oral hygiene behavior can positively modify the risks associated with conditions of poor oral health, especially periodontal disease and dental caries. In advanced stages of oral problems, such as a high number of dental caries or tooth loss, the attenuation of CV outcomes was not seen.
Masi and colleagues  note that the association between parameters of poor oral health and risk of CV disease has been reported often enough for periodontitis to be included in the group of potential conditions that increase the risk of CVD in the 2016 ESC Guidelines for CVD prevention. The results of Park et al. add to the evidence suggesting a potential impact of oral inflammatory disease on CV event risk, in addition to traditional CV risk factors. Moreover, they provide clinical evidence for a potential benefit in CV protection by the simple adoption of better oral health behaviors.
The biological pathways underlying the observed association remain to be elucidated, but Masi et al. speculate ‘that the systemic benefits obtained with improved oral health could depend on reduced exposure to chronic systemic inflammation’. The results, however, also suggest that other factors might be at play, in addition to inflammation. This is illustrated by the observation that dental caries are commonly associated with a lower systemic inflammatory exposure compared with periodontal diseases, but that in the current study they had a stronger association with CV events.
In recent years, more attention has been focused on microbiota-host interactions, as microbiota appear to play a role in CVD. The systemic inflammatory response associated with oral disease is thought to result from translocation of pathogenic bacteria from the oral cavity to the systemic circulation. A dysbiosis that leads to oral disease may also contribute to atherogenesis, and indeed oral bacteria have been isolated from atherosclerotic plaques.
Higher systemic oxidative stress may also play a role in the relation between oral health and CVD. On the one hand, it may modify the pattern of cytokines produced by immune-inflammatory cells, thereby hampering their capacity to contrast the bacterial effects on the oral cavity. On the other hand, chronic activation of these cells and exposure to elevated levels of oxidative stress may exhaust them, and ultimately lead to cellular aging.
The authors conclude that this is the first clinical evidence of the potential impact of better dental hygiene on future risk of CV events. This should be confirmed in large clinical trials evaluating the effect on hard clinical outcomes, and the underlying mechanisms remain to be established. But, ‘Given that periodontal diseases are the commonest form of inflammatory/infectious diseases worldwide, the public health benefits of promoting oral health are potentially large.’