Weight and weight change, and oral health in norwegian adults: longitudinal findings from the HUNT study

Oral diseases, such as dental caries and periodontitis, and obesity are both prevalent and share common risk factors. Although obesity, defined as body mass index (BMI) ≥30 kg/m2, has been associated with poorer oral health, the association between long-term average BMI, changes in BMI, and oral health status in adulthood remains unclear. This study aims to investigate the associations between long-term average BMI, changes in BMI, and self-rated oral health status in the adult Norwegian population. We conducted a prospective cohort study, comprising 17,088 individuals (58.6% females) who participated in the population-based Trøndelag health study (HUNT). The cohort was established using data from HUNT3 (2006-08), and participants were subsequently followed up for self-rated oral health status collected at HUNT4 (2017-19). At HUNT3 (the baseline), weight and height were measured directly, while retrospective data on weight and height were retrieved from measurements conducted at HUNT1 (1984-86) and HUNT2 (1995-97). Average BMI and BMI changes over 10- and 20-year periods were calculated. In addition, 10-year average waist circumference (WC) and corresponding WC changes were assessed. We estimated odds ratio (OR) with 95% confidence interval (CI) using multivariable logistic regression models after adjustment for potential confounders. In HUNT4, 1,500 participants (8.8%) rated their oral health as poor or very poor. The fully adjusted ORs for poor oral health among participants with an average BMI ≥30 kg/m² over 10- and 20-year periods were 1.5 (95% CI, 1.3–1.7) and 1.5 (95% CI, 1.3–1.8), respectively, when compared with normal weight individuals. However, after adjustment for baseline BMI, the associations between long-term average BMI and poor oral health were noticeably weakened. Additionally, compared with stable BMI, both BMI loss (≥2.5 kg/m²) and BMI gain (≥5 kg/m²) over 10-years were associated with poor oral health, with ORs of 1.6 (95% CI, 1.3–2.2) and 1.5 (95% CI, 1.2–1.9), respectively. We observed a similar but weaker pattern for average WC and changes in WC over 10-year period. Our findings suggest that average BMI ≥30 kg/m² over the long term and both BMI gain and BMI loss were associated with poorer oral health. However, the association with long-term average BMI and poor oral health was attenuated after adjustment for baseline BMI.