Association between periodontitis and diabetes

Background + Aims

• Type 2 diabetes mellitus (T2DM) is a metabolic disorder characterised by insulin resistance and elevated blood glucose levels, influenced by factors like obesity and inflammation.
• Periodontitis has been proposed as a potential risk factor for T2DM, though longitudinal studies are limited. Some research shows a link between periodontitis and T2DM risk, while others report mixed findings.
• Mechanisms may include systemic inflammation and oxidative stress, leading to insulin resistance.
• This study aims to examine the association between periodontal condition and the development of T2DM over a 15-year follow-up period.

Materials + Methods

• The study followed a cohort of individuals born in 1935 and living in Oulu, Finland, with baseline examinations conducted from 1990 to 1992 and follow-up in 2007–2008.
• At baseline, 780 individuals attended the baseline clinical assessments, including:
  • Diabetes screening through fasting blood glucose and 2-hour (75g) oral glucose tolerance tests (OGTT).
  • Periodontal assessments including probing pocket depth (PPD) measured at multiple tooth sites, and PPD ≥4 mm were recorded.
• Participants with baseline diabetes (n=59) were excluded. Of the remaining non-diabetic participants, 414 attended the follow-up, with 395 included in the final analysis after excluding those with incomplete data.
• Participants were categorised as:
  • Periodontally healthy (no deepened pockets)
  • Having moderate pockets (4–5 mm)
  • Having severe pockets (≥6 mm)
  • Edentulous (has no teeth)
  • Intra-examiner reliability for periodontal measurements was high, with kappa values of 0.78–0.80.
• The primary outcome was T2DM diagnosis during the follow-up, based on WHO and International Diabetes Federation criteria (fasting venous plasma glucose ≥7.0 mmol/L or 2-hour post-load venous glucose ≥11.1 mmol/L).
• Confounding variables were collected via questionnaires, interviews, and clinical examinations. They included:
  • Family history of diabetes
  • Physical activity
  • Diet
  • Smoking status
  • Body mass index (BMI)
  • Impaired glucose tolerance (IGT)
  • Serum triglycerides
  • HDL cholesterol
• Statistical analyses used modified Poisson regression to calculate rate ratios (RR) with 95% confidence intervals.
• Analyses were performed for the entire cohort and a subpopulation of non-smokers, with additional assessments of PPD as a continuous variable among dentate subjects.

Results

• The study population consisted of 395 participants from a baseline cohort in Oulu, Finland.
• At follow-up, 81 individuals (20.5%) developed T2DM.
• Incidence rates of T2DM were:
  • Periodontally healthy subjects: 15%
  • Those with moderate PPD (4-5mm): 21%
  • Those with severe PPD (≥6mm): 27%
  • Edentulous subjects: 19%
• Participants with more severe periodontal pockets at baseline tended to have:
  • A higher hereditary risk of diabetes
  • Lower physical activity
  • Less healthy diets.
• Smoking rates were higher among those with severe periodontal disease.
• Participants with deeper pockets or edentulousness had higher BMI and greater BMI changes during the follow-up period.
  • Hypertriglyceridemia, low HDL cholesterol, impaired glucose tolerance (IGT), and arterial hypertension were also more common in these groups.
• Multivariate analysis adjusted for confounders (e.g., gender, BMI, smoking, physical activity) showed an exposure-response relationship between periodontal pockets and T2DM risk. The non-significant, adjusted RR for T2DM, when compared to periodontally healthy subjects, was:
  • Those with PPD 4-5mm: RR 1.32
  • Those with PPD ≥6mm: RR 1.56
• Among dentate participants, each additional site with a deepened pocket slightly increased the risk of T2DM (adjusted RR 1.02).

Limitations