Research article
Prevention of Upper Respiratory Tract Infections by Gargling: A Randomized Trial

https://doi.org/10.1016/j.amepre.2005.06.013Get rights and content

Background

Gargling to wash the throat is commonly performed in Japan, and people believe that such hygienic routine, especially with gargle medicine, prevents upper respiratory tract infections (URTIs). Its effectiveness, however, has not been established by clinical trials.

Design

Randomized controlled trial carried out in 2002–2003 winter season and analyzed in 2003 and 2004.

Participants

Healthy volunteers (387) aged 18 to 65 years.

Intervention

Participants were randomly assigned to water gargling, povidone-iodine gargling, and usual care (control). Subjects in the two gargling groups were requested to gargle with water or diluted povidone-iodine at least three times a day. Participants were followed for 60 days.

Main Outcome Measures

The primary outcome measure was first URTI incidence. Severity of URTI symptoms among incident cases was also evaluated. Both outcomes were assessed with a self-administered symptom record. Analyses were performed on an intention-to-treat basis.

Results

A total of 130 participants contracted URTIs. The incidence rate of first URTI was 0.26 episodes/30 person-days among control subjects. The rate decreased to 0.17 episodes/30 person-days in the water gargling group, and 0.24 episodes/30 person-days in the povidone-iodine gargling group. Respective incidence rate ratios against controls were 0.64 (95% confidence interval [CI]=0.41–0.99) and 0.89 (95% CI=0.60–1.33). A Cox regression (proportional hazard model) revealed the efficacy of water gargling (hazard ratio=0.60, 95% CI=0.39–0.95). Even when a URTI occurred, water gargling tended to attenuate bronchial symptoms (p=0.055).

Conclusions

Simple water gargling was effective to prevent URTIs among healthy people. This virtually cost-free modality would appreciably benefit the general population.

Introduction

Upper respiratory tract infection (URTI) is one of the most common medical problems in the daily lives of otherwise healthy people. In the United States, people experienced 2.5 episodes, on average, every year.1, 2 However, corroborative evidence for URTI prevention is quite scarce. People, therefore, take measures on the basis of their own experience or preferences.

Gargling is generally accepted and strongly recommended as a preventive modality against URTI in Japan. A lot of people use gargle medicines such as povidone-iodine expecting virucidal effects.3, 4 Some simple questionnaire survey and nonrandomized studies suggested that frequent gargling with diluted povidone-iodine would reduce the incidence of URTI or influenza and the following absenteeism from schools or workplaces.5, 6, 7, 8 However, there have been no controlled trials, and it remained unresolved as to whether gargling was really effective.

To answer this simple question, a randomized controlled trial was conducted in community healthcare settings all over Japan.

Section snippets

Study Associates and Participants

In September 2002, authors invited applications for study associates through several relevant mailing lists from the Internet. Eighteen healthcare professionals who agreed with the purpose and protocol of the study were appointed local administrators. From December 2002 through January 2003, healthy adult volunteers were recruited for the study in the local administrators’ areas. The inclusion criteria were both genders, aged 18 to 65 years, and subjectively healthy. The exclusion criteria were

Results

Figure 1 is the flowchart of this study. A total of 387 subjects participated in the study at 18 sites (four in northern Japan, nine in the central region, and five in the western region; two to 52 persons per site) and were randomized. The follow-up period was 60 days between December 2002 and March 2003. Excluded from analysis were two subjects who already suffered from URTI on the first day of intervention, and one subject who did not write in the diary at all (follow-up 99%). Two subjects

Discussion

To our knowledge, this is the first randomized controlled trial to evaluate the effectiveness of gargling for the prevention of URTIs among healthy people. Authors found that simple water gargling would reduce the incidence rate of URTIs during 60 days in the prevalent season by 36%. Water gargling might also decrease supervening bronchial symptoms even if one contracted a URTI.

Whirling water is deemed to wash out pathogens from the pharynx and oral cavity. The incubation time of rhinovirus, a

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