A substantial proportion of cancers are preventable through modification of health-related behaviors, including smoking cessation and maintaining adequate oral hygiene. Previous studies suggested that health behaviors tend to cluster and may jointly influence cancer risk. However, limited research has examined the dynamic and reciprocal relationships between different behaviors over time, and most intervention strategies continue to target single behaviors in isolation. Understanding how behaviors such as smoking and toothbrushing influence one another may inform more effective and integrated approaches to cancer prevention. 

We analyzed data from a large, population-based survey conducted in China during 2021–2024, with baseline and 6-month follow-up assessments. Participants provided demographic information and health-related behaviors via the Smart Health Management Digital Platform for Primary Cancer Prevention (SmartHMDP-PCP). 

Multinomial logistic regression models were used to examine associations between smoking transitions and toothbrushing behavior patterns, as well as between toothbrushing transitions and smoking behavior patterns. Reciprocal relationships were further assessed using cross-lagged panel models implemented in the lavaan package in R. All models were adjusted for time-invariant covariates (sex, age group, body mass index, marital status, education level, urban-rural residency, history of periodontitis, and chronic diseases) and time-varying covariates (alcohol consumption, sugar-sweetened food and beverage intake, physical inactivity, low fruit and vegetable intake, unhealthy sleep pattern, lack of annual dental checkups, and absence of daily flossing). 

A total of 63,490 participants were included. At baseline, 9,799 (15.4%) reported a history of smoking, and 22,233 (35%) reported toothbrushing less than twice daily. At 6-month follow-up, these proportions declined to 4921 (7.8%) and 17,171 (27.0%), respectively. 

Multinomial logistic regression analyses suggested a bidirectional association between smoking transitions and toothbrushing patterns. Deterioration or improvement in toothbrushing was positively associated with corresponding deterioration or improvement in smoking behavior (OR 95% CI: 2.34, 1.74-3.15; 1.38, 1.26-1.50; P-values <0.001). Persistent smoking was associated with deterioration in toothbrushing (1.28, 1.11-1.47) and with persistently insufficient toothbrushing frequency (1.58, 1.45-1.72). 

Cross-lagged panel analyses confirmed the reciprocal relationship: baseline toothbrushing predicted smoking at follow-up (β= -0.016, P=0.048), and baseline smoking predicted toothbrushing at follow-up (β= -0.044, P<0.001 ). Both behaviors showed strong temporal stability, indicating habitual patterns over time.

This study provides evidence of a reciprocal relationship between smoking and oral hygiene behaviors among Chinese adults, with smoking exhibiting a stronger habitual persistence and a more pronounced directional influence on oral hygiene behaviors. These findings suggest that cancer prevention interventions may be more effective when they integrate oral health and general health behaviors within a unified behavioral framework, rather than addressing behaviors in isolation. Further research is warranted to confirm these relationships and to inform integrated, multi-behavioral prevention strategies.