Body mass index change and risk of poor oral health in Norwegian adults: the HUNT longitudinal study

Abstract Background Oral diseases and obesity share common risk factors and are highly prevalent. However, the relationships between body mass index (BMI), BMI change and oral health conditions in adults are less studied. In this study, we investigate the associations of long-term obesity and BMI change with risk of poor self-rated oral health among adults. Methods This study include individuals aged 29-90 years (57.8 % women, mean age at baseline, HUNT3, was 54.9 years) who participated in the first (HUNT1, 1984-86), second (HUNT2, 1995-97), third (HUNT3, 2006-08) and fourth (HUNT4, 2017-19) survey of the Trondelag Health Study (HUNT). Weight and height were measured at each survey. We estimated average BMI values and BMI change over a 10-year (HUNT2- HUNT3, N = 19,729) and 20-year (HUNT1- HUNT3, N = 14,276) period and linked to their information on oral health status at HUNT4. We employed logistic regression models with adjustment for confounders and computed odds ratio (OR) with 95 % Confidence Interval (CI). Results At HUNT4, 1812 (9.2 %) participants rated their oral health as poor or very poor. The multivariable-adjusted ORs for average BMI over 30 kg/m2 were 1.3 (95 % CI: 1.1-1.5) and 1.2 (95 % CI: 1.0-1.5) over a 10-year and 20-year period, respectively, when compared to normal weight. After adjustment for most recent BMI (HUNT4), the associations of long-term obesity with poor self-rated oral health weakened. Compared with stable BMI, both loss and gain in BMI over a 10-year period were associated with increased risk of poor oral health. In the adjusted analysis, we found that a BMI loss of more than 2.5 kg/m2 and a BMI gain of more than 5 kg/m2 was associated with 1.5 times (OR = 1.5, 95 % CI: 1.1-1.9) and 1.3 times (OR = 1.3, 95 % CI: 1.1-1.6) greater risk of poor oral health. Conclusions Our findings suggest that individuals with long-term obesity and BMI change have a markedly higher risk of poor self-rated oral health. Key messages • Long-term obesity was associated with increased risk of poor self-rated oral health. • Compared with stable body mass index (BMI), loss- and gain in BMI were associated with increased risk of poor self-rated oral health.