[The effect of oral care on natural immune function in the dependent elderly].

While oral care is known to play an important role in the prevention of aspiration pneumonia, its influence on immune function is unclear. In this study, we performed oral care on ten dependent elderly individuals and examined its influence on NK cell activity. The study duration was 12 weeks. During the first six weeks, the subjects cleaned their mouths as usual (control period). In the last six weeks, a dental hygienist performed oral care and denture cleaning three times a week (intervention period). The outcome measure was the quantity of oral bacteria and the detection rate of the microbe in connection with an opportunistic infection and NK cell activity before and after the intervention. Samples were collected at three time points: the beginning of the study, after the control period and before the intervention period (i. e., after six weeks), and after the intervention period (i. e., after 12 weeks). There was no significant difference in the number of oral bacteria between the control period and the intervention period. In contrast, while NK cell activity did not change during the control period, activity increased during the intervention period (p = 0.03). This finding suggests that rather than decreasing the number of oral bacteria, oral care increases NK cell activity.