Linear and non-linear associations of depressive symptoms with oral health knowledge, attitudes, and practices among rural older adults in China: a cross-sectional study.

Background: Depression affects the oral health of older adults; however, little is known about its impact on oral health among rural older adults in developing countries, which warrants further research. Taking China as an example, there is a large population base of rural older adults suffering from depression, and many rural older people also have long-term oral health problems, which have seriously affected their quality of life in later life. Therefore, this study aimed to explore linear and non-linear associations of depressive symptoms with oral health knowledge, attitudes, and practices among rural older adults in China.

Methods: From November 2020 to December 2020, 1,902 rural community-dwelling older people aged 60 years and older were investigated, via a cross-sectional survey. The general information, depressive status, oral health knowledge, attitudes, and practices of the participants were obtained through face-to-face structured questionnaires. Among them, the Zung Depression Self-Rating Scale was used to investigate the depressive symptoms of the participants in this survey. The generalized linear model and classification and regression tree model were used, separately.

Results: Based on linear analysis results, we found that minimal to mild depressive symptoms [regression coefficient (β) = -0.345; 95% confidence interval (CI): -0.582 to -0.109, P = 0.004] and depressive symptoms (β = -1.064; 95% CI: -1.982 to -0.146, P = 0.023) were significantly correlated with oral health knowledge. A negative correlation was observed between minimal to mild depressive symptoms (β = -0.385; 95% CI: -0.600 to -0.170, P < 0.001) and oral health attitudes. In addition, while both minimal to mild depressive symptoms (β = 0.018; 95% CI: -0.312 to 0.347, P = 0.916) and depressive symptoms (β = 0.604; 95% CI: -0.675 to 1.883, P = 0.355) were associated with oral health practices. Furthermore, the non-linear analysis showed a combined effect of depressive symptoms on oral health attitudes, indicating that older people of a younger age, not living alone, and not suffering from depressive symptoms are more likely to report better oral health attitudes.

Conclusion: Both the linear and non-linear analyses in our study showed that depressive symptoms are significantly correlated with the poor oral health attitudes of older adults in rural communities. Furthermore, depressive symptoms were associated with oral health knowledge in the linear analysis. However, no statistically significant difference was found between depressive symptoms and oral health practices in either analysis. This research deepens our knowledge and understanding of relevant evidence in the mental and oral health of people in later life. In addition, analyzing the factors that affect the oral health of older people from the perspective of their depressive status provides new thinking directions and scientific references for improving the oral health of older adults in practical life.