Testing the appropriateness of a multi-dimensional approach to assessing OHQoL

In assessing oral health related quality of life (OHQoL), existing measures are typically structured into multiple conceptual dimensions to provide individual domain scores. However, evidence of the appropriateness of structuring OHQoL measures into multi-dimensions is lacking. Objective: Through Structural Equation Modeling (SEM), this study aimed to compare the model fitting of multi-dimensional and uni-dimensional approaches to an OHQoL measure. Methods: Assessment of OHQoL was obtained using OHQoL-UK from 3,000 adults in a national survey conducted in the Republic of Ireland. OHQoL-UK consists of 16 items with a proposed 3-dimensional structure (physical, social, and psychological domains). In the uni-dimensional approach all items were regarded as in the same domain (OHQoL). In the multi-dimensional approach the 16 items were categorized into physical, social, and psychological domains of OHQoL. SEM (Lisrel 8.54) was applied to evaluate and compare the fitting of the measurement models for the OHQoL measure as a uni-dimensional structure compared to a multi-dimensional structure. Results: The multi-dimensional approach showed better model fitting than the uni-dimensional approach, for both the weighted and unweighted forms. Compared with the uni-dimensional approach, the multi-dimensional approach had significantly lower c² (2797.85 vs 4299.70 for unweighted scores; 3055.07 vs 4777.94 for weighted scores) and lower RMSEA values (0.097 vs 0.125 for unweighted scores; 0.102 vs 0.128 for weighted scores) (all p<0.001). Weighing did not improve the model fitting in any dimension (all p>0.05). In fact, as compared with weighted measures, unweighted measures appeared to have a better fitting for “physical well-being”, as evidenced by the significantly lower c² (118.23 vs 233.82) and lower RMSEA value (0.066 vs 0.094) (both p<0.001). Conclusion: In assessing OHQoL (at least with OHQoL-UK), a multi-dimensional approach is more appropriate than a uni-dimensional approach. The conceptual dimension of physical, social, and psychological domains of OHQoL-UK is supported as a valid structure.