Multicentered epidemiological study of factors associated with total bacterial count in the saliva of older people requiring nursing care

Aim: To clarify whether the number of present teeth, independent of other well-known factors, was associated with the total bacterial count in the saliva of older people requiring care at nursing homes in a multicentered epidemiological survey. Method: The participants were 618 older people (mean age 86.8 ± 6.9 years; 122 men, 496 women) residing in 14 nursing homes across Japan. The dependent variable was the participant's salivary bacterial count, and the independent variables were basic demographic data, oral conditions and activity of daily living (measured by Barthel Index). Statistical analysis was first carried out by Student's t-test, Pearson's correlation coefficient analysis and Spearman's rank correlation coefficient analysis. Independent variables found to have a significant relationship to their salivary bacterial count by the univariate analyses were further examined by stepwise multivariate analysis. Results: The independent variables shown by univariate analysis to have a significant positive relationship with higher salivary bacterial count were presence of food residue (P = 0.001), absence of mouth dryness (P = 0.001), need of oral care assistance (P = 0.001), inability to keep the mouth opened (P = 0.009), inability to gargle (P = 0.002), denture use (P = 0.004), higher number of present teeth (P = 0.006) and lower Barthel Index (P = 0.001). Subsequent multivariate analysis identified presence of food residue (P = 0.031), higher number of present teeth (P = 0.043) and lower Barthel Index (P = 0.001) as independent associated factors for higher salivary bacterial count. Conclusions: The present study found that presence of food residue, higher number of present teeth and decreased activity of daily living were significantly related to higher bacterial count in the saliva of older people requiring care. Geriatr Gerontol Int 2017; 17: 219–225.