Gargling with tea catechin extracts for the prevention of influenza infection in elderly nursing home residents: a prospective clinical study.

OBJECTIVES To evaluate the effects of gargling tea catechin extracts on the prevention of influenza infection in elderly nursing home residents. DESIGN A prospective study conducted for 3 months from January to March 2005. SETTINGS/LOCATION A nursing home in Japan. SUBJECTS A total of 124 elderly residents of at least 65 years of age were enrolled in the study. Seventy-six residents (83 +/-8.2 years, mean +/-standard deviation; 24 men, 52 women) gargled with tea catechin extract (catechin group) and were compared with 48 age- and sex-matched residents who gargled without tea catechin extracts (control group). All the residents were vaccinated with an influenza vaccine until early December 2004. INTERVENTIONS catechin group: gargling with the tea catechin extract solution (200 microg/mL catechins, 60% of catechins comprise epigallocatechin gallate); control group: gargling without the catechin extract solution. In both groups, gargling was performed three times daily for 3 months. OUTCOME MEASURES The incidence of influenza infection during the study was compared between the two groups. A safety evaluation was conducted to observe adverse events during the study. RESULTS The incidence of influenza infection was significantly lower in the catechin group (1.3%, one resident) than in the control group (10%, five residents) calculated by multivariate logistic regression analysis (p = 0.028; odds ratio, 15.711; 95% confidence interval, 1.883-399.658). No adverse events, such as respiratory tract irritation, an obstruction, or allergic bronchial spasm, were observed during the study. CONCLUSIONS This prospective study demonstrating the effect of catechin gargling on the prevention of influenza infection in the elderly is the first to be reported in the literature. Further randomized, controlled studies are needed to confirm the effects of catechin gargling on the prevention of influenza infection.