# Lifestyle, Inflammation, and Periodontitis: A National Study Based on the Life’s Crucial 9 Framework

## TL;DR

Better lifestyle habits are linked to less severe periodontitis, mainly through reduced inflammation.

## Contribution

This study shows that lifestyle factors reduce periodontitis risk via inflammatory pathways.

## Key findings

- Higher LC9 scores correlate with lower periodontitis risk and severity.
- Tobacco use and glycemic control are the strongest contributors to periodontal health.
- Systemic inflammation, not oxidative stress, mediates the LC9-periodontitis link.

## Abstract

To examine the association between the Life’s Crucial 9 (LC9) lifestyle score and periodontitis severity among U.S. adults, and to explore the mediating roles of systemic inflammation and oxidative stress. The study hypothesis is that higher LC9 scores are associated with lower periodontitis severity.

This cross-sectional study used data from 7124 adults aged ≥30 years from the 2009–2014 National Health and Nutrition Examination Survey (NHANES). Weighted logistic, ordinal logistic, and linear regression models assessed the relationships between LC9 and periodontitis risk, severity, clinical attachment loss (CAL), and probing depth (PD). Restricted cubic spline (RCS) regression examined dose–response trends. Weighted quantile sum (WQS) regression evaluated the relative contribution of LC9 components. Mediation analysis was performed to assess inflammatory and oxidative pathways. Receiver operating characteristic (ROC) analysis compared the predictive performance of LC9 and Life’s Essential 8 (LE8).

Each 10-point increase in LC9 was associated with a reduced risk of periodontitis (OR = 0.858, 95% CI: 0.808–0.911), milder severity, and lower CAL and PD. Tobacco exposure and glycemic control were the strongest contributors. White blood cell count, systemic inflammation index (SIRI), and albumin mediated 25.1%, 7.3%, and 5.3% of the LC9–periodontitis relationship, respectively. No statistically significant mediation was observed for oxidative stress. LC9 and LE8 demonstrated comparable predictive performance (AUC: 0.758 vs 0.759).

Higher LC9 scores were statistically significantly associated with better periodontal outcomes, primarily through inflammatory pathways. Clinically, modifying key lifestyle factors — especially tobacco avoidance and glycemic control — may effectively reduce periodontitis risk.