title: Risk factors of periodontitis in Australian adults
Creators: name: Khan, S
Publisher: name: University of Tasmania
Year: 2020

description: Background: Overweight/obesity and periodontitis are complex health problems, contributing to a high burden of co-morbidities that have a significant economic impact in Australia and worldwide. Although international studies have compared the relationship between these two complex conditions, there is a dearth of research literature reporting their association in the Australian population. The aims of this PhD were to explore the relationship between overweight/obesity and periodontitis in Australian adults; and to determine if there are mediators of this relationship. The objective of the first project was to determine the association between overweight/obesity and periodontal disease in young adults and adolescents by a systematic review. Twelve databases were searched using MeSH terms for “overweight or obesity” and “periodontitis”. Quality appraisal was conducted using the Newcastle Ottawa scale. Of the 25 eligible studies, 17 showed an association between overweight/obesity and periodontitis (Odds Ratios ranged from 1.1 to 4.5). However, there was a gap in the Australian data on the relationship between obesity and periodontitis. Hence, an analysis using STATA 15 of the cross-sectional National Survey of Adult Oral Health (NSAOH) 2004-06 was conducted (n = 3715 participants). Body Mass Index (BMI) was calculated using self-reported body height (cm) and body weight (kg). Overweight/obesity was defined as BMI ≥25kg/m\(^2\) [a combined variable of overweight “BMI ≥25-29.9 kg/m\(^2\)” and obesity (BMI ≥25kg/m\(^2\))]. Putative confounders included thirteen dietary questions, age, sex, education, annual income, smoking, alcohol intake, oral hygiene behaviours and dental visiting behaviour. The mean number of sites with probing depth (PPD)≥4mm, clinical attachment loss (CAL)≥4mms were used to measure the extent and the CDC/AAP case definition was used to measure the prevalence of periodontitis. Bivariate analysis found a significant association between extent of periodontitis and BMI. Multiple variable analysis indicated that periodontitis (prevalence and extent) was not associated with overweight/obesity when controlled for putative confounders. These results could be false due to the limitation of multiple variable regression analysis that groups putative confounders/mediators as a cluster in determining the effect of exposure on outcome. Therefore, this dissertation utilised single mediation analysis to determine the relationship between overweight/obesity and periodontitis using all NSAOH participants aged 30 years or older. A Direct Acyclic Graph was constructed. Dental visiting behaviour (a de facto measure of healthy behaviour) was used as a mediator. Confounding variables included age, sex, household income, education, diabetes, alcohol intake and smoking. Overweight/obesity was defined as physical inactivity induced overweight/obesity (BMI ≥25 kg/m\(^2\) and no moderate physical activity). Data was analysed using STATA 15 using the paramed library. Pathway effect analysis using potential outcomes illustrated that the effect of overweight/obesity on periodontitis, which was not mediated by poor dental visiting behaviour, was 10%. The indirect effect of overweight/obesity on periodontitis, mediated through poor dental visiting behaviour, was 3%. A limitation of the NSAOH 2004-06 was the potential participant under-reporting of chronic health conditions. A cross-sectional pilot study [a trial for measuring feasibility for the future prospective cohort study] was therefore designed, with a healthy cohort of obese people with no co-morbidities, that aimed to determine the relationship between overweight/obesity, diet, prediabetes and periodontitis. This study was part of a larger randomised controlled trial at the University of Sydney. The inclusion criteria were: aged 18 years and older, a body mass index ≥ 25 kg/m\(^2\) and pre-diabetic (fasting plasma glucose levels ≥ 5.6-6.9 mmol/L and/or two-hour post-challenge (oral glucose tolerance test) plasma glucose levels ≥ 7.8-11.0 mmol/L and/or HbA1c ≥ 5.7-6.4%), dentate (with at least eight teeth present) and no risk of infective endocarditis. Data was collected from 33 participants for age, sex, smoking, BMI, waist and hip circumference, PPD, CAL, BOP, oral hygiene behaviours, the usual reason for dental visiting, blood levels of highly sensitive C-reactive protein, glycosylated haemoglobin, lipid profile and apolipoprotein. Bivariate analysis using the R statistical package found waist circumference and fasting plasma glucose were significantly associated with periodontitis. No significant association was observed between BMI and periodontitis. Conclusions: Of the 25 eligible studies in the systematic review, 17 showed an association between obesity and periodontitis. However, there was a gap in the Australian data on the relationship between overweight/obesity and periodontitis. Conventional multivariable analysis of the NSAOH 2004-06 data found no significant association between overweight/obesity and periodontitis. Single mediation analysis to determine the relationship between overweight/obesity and periodontitis using a NSAOH subset of 3715 participants aged 30 years or more found that the effect of overweight/obesity on periodontitis, which was not mediated by poor dental visiting behaviour, was 13%. There was a positive association between waist circumference and periodontitis in the pilot study, which was part of a larger randomised controlled trial at the University of Sydney. To reproduce these outcomes, a prospective cohort study is required.