Association of healthy lifestyle with tooth count among adults aged 20 years and above: a cross-sectional study

While healthy lifestyle has been extensively studied in relation to chronic non-communicable diseases and lifespan, its impact on oral health remains insufficient. This study aimed to examine the association between healthy lifestyle and tooth count, and identify key risk factors. Data from 18,919 adults aged ≥ 20 years in the National Health and Nutrition Examination Survey (NHANES) 2005–2018 were analyzed. Participants were categorized into low, medium, and high adherence groups based on their compliance with healthy lifestyle factors. Multiple linear regression and restricted cubic splines were used to assess associations between healthy lifestyle scores and tooth count. Subgroup analyses were performed to identify sensitive populations. Subsequently, five indices, each excluding one different lifestyle factor, were constructed to calculate the strength of their associations with tooth count and to assess the key influencing factors. After adjusting for covariates, the medium (β = 1.13, 95%CI = 0.77, 1.49) and high adherence groups (β = 1.65, 95%CI = 1.20, 2.09) had significantly more teeth than the low adherence group. Each 1-unit increase in the healthy lifestyle score was associated with a 0.49 (95%CI: 0.37, 0.61) increase in tooth count. Results from restricted cubic splines confirmed this trend. The association was strongest in adults aged ≥ 65 years (P for interaction <0.01). Removing smoking from the lifestyle score attenuated the association most prominently. Healthy lifestyle is significantly associated with retaining more teeth among the American population, particularly among older adults. Smoking cessation appears to be a critical modifiable factor for preserving tooth count.