Circadian rhythms and influencing factors of xerostomia among Parkinson's disease patients.

PD patients suffer from xerostomia, dysphagia, and drooling. Subjective dysphagia is associated with drooling and xerostomia, but drooling prevalence or intensity does not influence xerostomia symptoms. Tremor, dyskinesia, and disease duration, which characterise PD, affect xerostomia. Additionally, food intake, sleep, age, LEDD, and daytime (peaks at 9 a.m. and 9 p.m.) increase xerostomia occurrence. This knowledge may improve dentists' advice to patients and aid development of patient-centred, symptom-relieving products.