Oral health behavior among 
25‐year‐old‐Norwegian adults: factor structure, factorial invariance over time and trends

BACKGROUND: Exploratory factor-analytical studies suggest that health behaviors are multidimensional, leading to hypotheses that such behaviors are bi- or tri-dimensional. This study applies confirmatory factor analysis (CFA), to semi-longitudinal data and provides new information about the factor structure of oral health-related behaviors among 25-year-old Norwegians. The purposes of the study were to (1) evaluate the factor structure of oral health behaviors and its invariance over time, (2) assess temporal changes in patterns of oral health behaviors and in their socioeconomic distribution between 1997 and 2007. METHODS: Simple random samples of 1190 residents born in 1972 and 8000 residents born in 1982 were drawn from the populations of three counties in Western Norway in 1997 and 2007. Structured questionnaires were mailed to the eligible participants. After one reminder, 735 (58% women, response rate 62%) and 1509 (63.3% women, response rate 19%) replied. RESULTS: A correlated three-factor model with cross-loadings showed a better fit than a two-factor model to both the 1997 sample: chi(2)/df = 2.1, CFI = 0.95, RMSEA = 0.03 and the 2007 sample: chi2/df = 3.1, CFA = 0.95, RMSEA = 0.04. Multiple-group CFA showed an acceptable fit for the unconstrained model, CFA = 0.95, RMSEA = 0.03, and no statistically significant difference in fit between the unconstrained and constrained models (P = 0.739). Multiple binary logistic regression with three sum scores based on the behavioral factors sugar intake, drug use and oral health-enhancing behavior revealed that the odds ratios for frequent sugar intake (OR = 0.6, 95% CI: 0.5-0.8) and oral health-enhancing behavior (OR = 0.6, 95% CI: 0.5-0.7) were less in 2007 than in 1997. Drug use remained stable over time (OR = 0.9, 95% CI: 0.7-1.1). Educational differences in sugar intake observed in 1997 had leveled off in 2007. CONCLUSION: A three-factor structure fitted the data in 1997 and 2007 and the factor structure was invariant over time. This suggests that oral health behaviors should be addressed jointly in oral health promotion programs.