Association between the Frequency of Daily Toothbrushing and Development of Nonalcoholic Fatty Liver Disease

<b><i>Background &amp; Aim:</i></b> This study aimed to evaluate the association between the frequency of daily toothbrushing and the development of nonalcoholic fatty liver disease (NAFLD). <b><i>Methods:</i></b> A retrospective longitudinal study was conducted from 2005 to 2012 at the Center for Preventive Medicine at St. Luke’s International Hospital, Japan. Data on all participants who underwent a health checkup during the study period were collected. NAFLD was diagnosed by abdominal ultrasonography, and all participants who were diagnosed with NAFLD at the time of their initial visit, consumed alcohol in any amount, or had received only one health checkup were excluded. The questionnaire for the frequency of daily toothbrushing was conducted as part of health checkups. The primary outcome was the risk of developing NAFLD according to the frequency of daily toothbrushing (1–2 times a day or 3 times a day) compared to those who brush teeth once or less than once a day. <b><i>Results:</i></b> Data were collected from 25,804 people. A total of 3,289 (12.7%) participants developed NAFLD. The mean age was 45.2 years, and 6,901 (26.7%) of the participants were male. The risk of developing NAFLD significantly decreased with increased frequency of daily toothbrushing. Adjusted odds ratios (ORs) are as follows: brushing teeth 1–2 times a day (OR: 0.85, 95% confidence interval [CI]: 0.77–0.95) and 3 times a day (OR: 0.74, 95% CI: 0.67–0.82). <b><i>Conclusion:</i></b> Frequent toothbrushing was shown to significantly reduce the risk of developing NAFLD.