Repeated use of over-the-counter (OTC) mouthwash was linked to a higher risk of developing prediabetes and diabetes in a study of more than 1,000 overweight/obese adults. The full findings were published in the journal Nitric Oxide.

For many individuals, use of OTC mouthwash is part of their regular oral hygiene care. The potential adverse effects of long-term daily use, however, have not been investigated. Study authors explained that using antibacterial mouthwash can eradicate oral microbes needed for nitric oxide formation and place the user at risk for metabolic disorders. 

To evaluate this association, they conducted the San Juan Overweight Adults Longitudinal Study (SOALS) among 1,206 overweight or obese adults aged 40–65 years; patients were followed for 3 years. Patients had no diabetes or major cardiovascular disease; 945 patients had complete follow-up data for analyses. Hazard ratios (HR) were adjusted for baseline age, sex, smoking, physical activity, waist circumference, alcohol consumption, and hypertension. 

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The data showed that 43% of patients used mouthwash at least once a day and 22% used mouthwash at least twice a day. Adults who used mouthwash at least twice a day at baseline showed a significantly increased risk of prediabetes/diabetes vs. those who used it less frequently (HR 1.67, 95% CI: 1.24–2.26) or never used mouthwash (HR 1.65, 95% CI: 1.19–2.28). The size of the effects were consistent after factoring in income, education, oral hygiene, oral conditions, sleep breathing disorders, diet, medications, HOMA-IR, fasting glucose, 2-hour post-load glucose, or C-reactive protein to the multivariate models. 

“Both associations were significant among never-smokers and obese,” added lead author Kaumudi J. Joshipura. 

Study participants who used mouthwash less than twice a day did not demonstrate a risk, suggesting that the effect starts at a threshold of use of twice a day or more. 

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