Objective  To explore the relationship and internal mechanism between sleep quality, oral health and mental health of the older people with chronic diseases in rural Shandong, China.

  Methods  Using stratified multistage cluster sampling, face-to-face interviews were conducted among 2 064 rural people aged 60 years and above and with chronic diseases in Shandong province during July – August 2020. Oral Health Impact Profile-5 (OHIP-5), Kessler Psychological Distress Scale (K10) and Pittsburgh Sleep Quality Index (PSQI) were adopted in the survey. Statistical analyses were performed with IBM SPSS 24.0.

  Results  For all the respondents, the median score (25th percentile, 75th percentile) was 9 (6, 13) for PSQI, 2 (0, 5) for OHIP, and 18 (12, 25) for K10. The sleep quality and oral health were positively correlated with mental health (r_s = 0.43, P < 0.001; r_s = 0.20, P < 0.001); sleep quality was positively correlated with oral health (r_s = 0.17, P < 0.001). The results of mediating effect analysis revealed that sleep quality played a partial mediation effect on the association between oral health and mental health, with an effect value of 95% confidence interval of 0.09 – 0.17 and accounting for 32.50% of the total effect.

  Conclusion  Sleep quality is a mediator between oral health and mental health among rural older people with chronic diseases; improving oral health and reducing sleep disorders may improve mental health in the population.