Association Between Childhood Asthma and Oral Health-Related Quality of Life in Young Children: A Cross-Sectional Study Using the SOHO-5

Aim: Asthma is a chronic condition with high prevalence in pediatric populations and may negatively influence oral health. The primary aim of this study was to evaluate the association between asthma and oral health-related quality of life (OHRQoL) in Portuguese children aged 6 to 8 years. Secondary aims included comparing caries experience, salivary parameters, and other clinical oral health indicators between asthmatic and non-asthmatic peers. Materials and Methods: A cross-sectional study was conducted with 89 child–parent pairs using a convenience sampling approach. Children with asthma were recruited from a hospital immunoallergology service, and healthy controls were recruited from a primary school. Data collection included parent-administered questionnaires on sociodemographic and behavioral factors, the Portuguese version of the SOHO-5 (child self-report and parent proxy forms), and standardized intraoral examinations assessing caries (WHO criteria, 5th edition), malocclusion, gingival bleeding, dental erosion, mucosal lesions, and molar–incisor hypomineralization. Stimulated salivary flow was measured. Bivariate statistical analyses and multivariable regression models were performed using SPSS (v.29), with a significance level set at p < 0.05. Results: Asthmatic children had significantly higher caries prevalence in both primary (52.6% vs. 27.5%, p = 0.027) and permanent dentition (32.4% vs. 0%, p < 0.001), as well as higher mean dmft scores (2.68 vs. 1.14, p = 0.026), reduced stimulated salivary flow (78.9% vs. 41.2% with low flow, p < 0.001), and worse child-reported SOHO-5 scores (mean 2.42 vs. 1.25, p = 0.004). After multivariable adjustment, asthma remained a significant independent predictor of low salivary flow (OR = 4.017, 95% CI: 1.443–11.178, p = 0.008), while the association with caries was attenuated and no longer significant (OR = 1.345, p = 0.590). Pain experience in the past year was the strongest predictor of OHRQoL across all multivariable models (SOHO-5 child: B = 1.583, p = 0.006; SOHO-5 total: B = 4.970, p < 0.001), indicating that children with pain history reported substantially worse OHRQoL. After adjustment, asthma did not reach statistical significance for either child-reported (B = 0.732, p = 0.090) or total OHRQoL scores (B = 0.693, p = 0.293). These findings should be interpreted cautiously given the limited number of covariates included in the models, constrained by the available sample size. Conclusions: Within the limitations of this cross-sectional study, including a small and non-probabilistic sample, asthmatic children presented a higher caries burden and a markedly higher prevalence of low stimulated salivary flow compared with non-asthmatic peers. Asthma remained a significant independent predictor of low salivary flow after multivariable adjustment, while the association with caries was attenuated, suggesting partial confounding by dietary habits. These findings highlight the importance of integrating oral health surveillance into the routine care of asthmatic children, with particular attention paid to salivary function and caries prevention.