Stability of oral health-related behaviour in a Norwegian cohort between the ages of 15 and 23 years

Objective: To assess the stability in self-reported oral health behaviour in a Norwegian cohort between the ages of 15 and 23 years. Methods: Self-administered questionnaires were used as part of a longitudinal cohort study. In 1992, a representative sample of 963 15-year-old adolescents participated, of which 676 (70%) and 567 (58%) remained in the study at ages 18 and 23 years. A total of 389 (40% of baseline) participated at each data collection, i.e. at ages 15, 18, 19, 21 and 23 years. Results: General linear model (GLM) repeated-measures ANOVA revealed statistically significant main effect of time with respect to soft drink and sweet consumption (F=22.4, P < 0.001 and F=4.3, P < 0.05, respectively). Adjusted mean scale scores of soft drink intake increased from 2.3 at age 15 years to 3.4 at age 23 years. The corresponding figures for consumption of sweets were 2.6 and 2.8. Two-way interactions achieved statistical significance with gender for soft drink consumption and toothbrushing. GLM repeated-measures with each gender revealed that soft drink consumption increased with time more extensively in boys (from 2.9 to 4.2, F=13.5, P < 0.001) than in girls (from 1.9 to 2.6, F=8.1, P < 0.001). Tracking or maintenance across time of the relative ranking at age 15 years occurred with all the four behaviours investigated. A total of 68-92% remained active and inactive regarding soft drink and sweet consumption, flossing and toothbrushing. Conclusion: The results provide evidence of tracking and early consolidation of oral health behaviour. This adds support for the assumption given for early intervention to prevent oral diseases.