Research Square · Oct 27, 2026
Nighttime Toothbrushing and Hypertension Among Korean Adults: Exploring the Role of Systemic Inflammation
By Kim M, Lee N, Ahn C et al.
Because salivary clearance and antimicrobial defenses decline during sleep, allowing overnight bacterial accumulation and periodontal inflammatory activity, nighttime oral hygiene may be particularly important; however, its association with hypertension remains largely unexplored. We investigated whether nighttime toothbrushing is associated with hypertension, and whether systemic inflammation mediates this association. We analyzed the cross-sectional 2016 to 2023 Korea National Health and Nutrition Examination Survey (KNHANES), including 33,224 adults, using survey-weighted analyses. Participants were classified as Night (brushing teeth after dinner or before bedtime) or None. After adjustment for morning and lunch brushing and risk factors, nighttime toothbrushing was associated with lower odds of hypertension (OR, 0.790; 95% CI, 0.686–0.910; P = 0.001). The association was present at both low (OR, 0.830; 95% CI, 0.702–0.982; P = 0.030) and high daytime brushing frequency (OR, 0.710; 95% CI, 0.555–0.908; P = 0.006), with no significant interaction (P for interaction = 0.299). In mediation analysis, the association was partly mediated by white blood cell count (indirect effect, − 0.539 percentage points; 95% bootstrap CI, − 0.837 to − 0.296; P = 0.004). Nighttime toothbrushing was associated with lower odds of hypertension, supported by a WBC-related inflammatory pathway. These findings suggest that nighttime toothbrushing may represent a simple, modifiable behavior warranting further investigation in hypertension.