Risk Factors Associated with Dry Mouth in Dependent Japanese Elderly

Objectives: To identify comprehensive risk factors, including oral health care and lifestyle-related factors, associated with dry mouth in dependent elderly and to compare  these factors between individuals <85 and ≥ 85 years of age.

Methods: We conducted a cross-sectional study involving 387 dependent elderly individuals at eight long-term care facilities and hospitals in Japan between March 2010 and February 2011. The primary outcome was tongue dorsum moisture using the KISO-Wet system. The potential 33risk factors were extracted from following six categories: 1) Individual characteristics, 2) Institutional characteristics, 3) Oral care characteristics, 4) Lifestyle characteristics, 5) Oral health characteristics, 6) Medication characteristics. Multivariate logistic regression analysis was conducted to examine the relationship between potential risk factors and dry mouth. The odds ratios were calculated together with the 95% CIs. The level of statistical significance was set at 0.05.

Results: Multiple logistic regression analysis identified five factors which were significantly associated with dry mouth among all study participants: low BMI, severity of physical disability, mouth breathing, high daily hours of sleep, and administration of diuretics. In the < 85-year-old group, significant associations with dry mouth were detected in severity of disability, mouth breathing, daily water consumption, teeth brushing frequency, measurement time, and the use of diuretics and anti-depressants. In the ≥ 85-year-old group, only low BMI, and the severity of physical disability were identified as significant factors of dry mouth. 

Conclusions: Our study has detected a link between teeth brushing frequency and dry mouth.To our knowledge, this is the first study to identify a link between teeth cleaning frequency and dry mouth, and suggests that teeth brushing should be encouraged in high-risk dependent elderly (< 85-year-old), particularly those taking antidepressants and/or diuretics.