Combined association of chewing capacity and depression with constipation: a cross-sectional study

Abstract

Background: This study aimed to investigate the independent and combined effects of chewing capacity and depression on the risk of constipation, using data from the National Health and Nutrition Examination Survey (NHANES) 2005–2010. Methods: A total of 10,814 participants were included in the analysis. Chewing capacity was assessed using functional tooth units (FTUs), defined as the number of functional posterior occlusal units, and categorized into three groups (≤ 3, 3–9, and 10–12). Depression was defined as a Patient Health Questionnaire-9 (PHQ-9) score of 10 or higher. The PHQ-9 is a widely used self-administered instrument that assesses the severity of depressive symptoms over the preceding two weeks. Constipation was determined based on the Bristol Stool Form Scale (BSFS) and bowel movement. Multivariable logistic regression models were used to estimate odds ratios (ORs) for constipation. A restricted cubic spline (RCS) analysis was conducted to evaluate dose–response relationships. Results: Participants with lower FTUs and higher PHQ-9 scores had a significantly increased risk of constipation. In multivariable-adjusted models, individuals with FTUs 10–12 exhibited a lowest constipation risk (OR = 0.637, 95% CI: 0.504–0.806), while depression was also strongly associated with constipation (OR = 1.942, 95% CI: 1.602–2.356). The joint analysis revealed that participants with both FTUs ≤ 3 and depression had the highest constipation prevalence (OR = 2.363, 95% CI: 1.600–3.489). Mediation analysis indicated that depression partially mediated the relationship between FTUs and constipation. Conclusion: Both impaired chewing capacity and depression were independently linked to a higher likelihood of constipation, and their co-occurrence appeared to exert a synergistic impact. These findings highlight the importance of integrating oral health rehabilitation and mental health interventions to prevent and manage constipation in at-risk populations.