The study was led by Suzuna Shiomizu of the Health Promotion Division of Kasugai City Hall, working with colleagues at Hiroshima University and Nagoya University Graduate School of Medicine. The team drew on data from 4,840 participants, including 3,290 men and 1,550 women, who underwent health examinations at the Seirei Preventive Health Center in Japan. The participants ranged in age from 35 to 69 years, with a median age of 53. As part of the broader Japan Multi-Institutional Collaborative Cohort, known as J-MICC, this population offered researchers a rare opportunity to examine lifestyle behaviors in fine detail among a large, well-characterized group of working-age and older adults.

To measure meal timing regularity, the researchers used a self-administered questionnaire that asked participants whether their meals occurred at consistent times across four separate dimensions: weekday lunch, weekday dinner, weekend lunch, and weekend dinner. Each dimension was categorized simply as regular or irregular. The oral health behaviors under scrutiny were equally concrete. Participants reported how often they brushed their teeth, whether they used interdental cleaning devices such as floss or interdental brushes, and whether they received professional dental cleanings. These three behaviors form the backbone of standard preventive dentistry recommendations worldwide, including guidance from the World Health Organization on oral disease prevention.

The raw numbers revealed that outright irregular meal timing was relatively uncommon in this health-conscious population. Only 1.8 percent of participants reported irregular weekday lunches, 1.4 percent reported irregular weekday dinners, 2.2 percent reported irregular weekend lunches, and just 0.9 percent reported irregular weekend dinners. That scarcity makes the associations that emerged all the more striking. Even a small group of people with erratic eating schedules showed a markedly different pattern of oral care, hinting that meal timing may act as a sensitive marker for broader lifestyle stability.

Using multivariable-adjusted logistic regression, a statistical technique that estimates the odds of an outcome while accounting for other influencing factors, the researchers found that irregular weekday dinner timing was associated with brushing less than twice daily, with an odds ratio of 2.05 and a 95 percent confidence interval of 1.19 to 3.54. Irregular weekend lunch carried an even stronger signal, with an odds ratio of 2.28 and a confidence interval of 1.45 to 3.57, while irregular weekend dinner showed an odds ratio of 2.09 with a confidence interval of 1.07 to 4.08. In practical terms, people whose meals drifted across the calendar were about twice as likely to fall short of the twice-daily brushing benchmark that dentists consider a minimum standard.

The link extended beyond brushing, though in a more fragile form. Irregular weekend dinner timing was also associated with less frequent use of interdental cleaning devices, showing an odds ratio of 2.25 with a confidence interval of 1.02 to 4.96. However, when the researchers applied their full statistical adjustment, the associations involving weekend dinner, both for tooth brushing and for interdental cleaning, were attenuated and no longer reached statistical significance. The connections between weekday dinner and weekend lunch irregularity and tooth brushing frequency, by contrast, remained robust even after full adjustment. Notably, no significant relationship was found between meal timing regularity and professional dental cleaning, suggesting that irregular eaters do not necessarily skip the dentist; they simply falter in the small, daily rituals that happen at home.

Why would the timing of meals and the habit of brushing teeth travel together? The authors propose that regular meal timing may serve as a marker of stable daily routines more generally. A person who eats lunch at noon every day, including lazy Sunday afternoons, likely organizes the rest of life around predictable anchors as well. Tooth brushing is what behavioral scientists call a habit cued by context: it is triggered by waking, by finishing a meal, and by going to bed. When meals float unpredictably, those cues weaken, and the automatic chain of events that ends with a toothbrush in hand can break down. Weekend patterns may matter especially because weekday schedules are often enforced by work, while weekends expose the true flexibility, or fragility, of a person’s routine.

There is also a plausible biological pathway worth considering. Dental caries and periodontal disease both depend on the frequency and timing of sugar and food exposure in the mouth. Each eating episode lowers oral pH and feeds acid-producing bacteria, so erratic eating can mean more frequent acid challenges to enamel. If irregular eaters also brush less often, the two effects could compound, leaving teeth exposed to acid for longer stretches with less mechanical removal of plaque. The new study did not measure dental outcomes directly, so this compounding remains a hypothesis, but it aligns with established models of how caries develop and why dentists emphasize both brushing frequency and the spacing of meals and snacks.

The researchers are careful about what the data can and cannot show. Because the study is cross-sectional, capturing a single snapshot in time, it cannot establish whether irregular meal timing causes poor oral hygiene or whether both simply spring from a common root, such as lower conscientiousness, shift work, psychological stress, or disrupted circadian rhythms. Reverse causation is also conceivable: someone with painful dental problems might abandon regular meals, though the modest prevalence of irregular timing makes this less likely to drive the whole signal. The authors explicitly state that causal inference is not possible from this design, and the attenuation of some associations after full adjustment underscores the need for caution when interpreting the weaker findings.

Even with those caveats, the study opens an intriguing public health avenue. Oral diseases remain among the most common chronic conditions globally, and simple, scalable markers that identify people at risk of neglecting daily hygiene could sharpen prevention efforts. If meal timing regularity proves to be such a marker in longitudinal and intervention studies, a single question about weekend eating habits could flag patients who need extra encouragement toward twice-daily brushing and interdental cleaning. For the rest of us, the message is refreshingly mundane: keeping breakfast, lunch, and dinner anchored to the same hours, even on Saturdays and Sundays, may quietly reinforce the small habits that keep teeth and gums healthy for decades. The clock, it turns out, may be an unsung ally of the toothbrush.

Subject of Research: The association between meal timing regularity and oral health behaviors in Japanese adults

Article Title: Association between meal timing regularity and oral health behaviors

Article References: Shiomizu, S., Mitsui, M., Furuie, A., Wei, H., Matsuo, K., Asaeda, M., Kurawaki, Y., Nishimura, R., Nagayoshi, M., Tamura, T., Wakai, K., & Naito, M. (2026). Association between meal timing regularity and oral health behaviors. BMC Public Health. https://doi.org/10.1186/s12889-026-29820-w

Image Credits: AI Generated

DOI: 10.1186/s12889-026-29820-w

Keywords: meal timing regularity, oral health behaviors, tooth brushing frequency, interdental cleaning, professional dental cleaning, cross-sectional study, BMC Public Health, chrononutrition, public health, preventive dentistry, J-MICC cohort, Japan