# Association Between Domain-Specific Physical Activity and Novel Inflammatory Biomarkers Among US Adults: Insights From NHANES 2007–2018

## TL;DR

This study finds that leisure-time and transportation-related physical activity are linked to lower inflammation in adults, while occupational activity is not.

## Contribution

The study introduces novel insights on how specific types of physical activity affect newly identified inflammatory biomarkers in US adults.

## Key findings

- Leisure-time MVPA meeting guidelines is negatively associated with systemic inflammatory biomarkers.
- Transportation-related MVPA is linked to reduced SII and SIRI levels.
- BMI mediates the relationship between physical activity and inflammation.

## Abstract

Objectives: The novel inflammatory biomarkers, including systemic immune-inflammation index (SII), systemic inflammation response index (SIRI), and neutrophil-to-lymphocyte ratio (NLR), can contribute to predicting the future risk of various diseases. However, the impact of different physical activity (PA) domains on systemic inflammation remains unclear. The study aims to investigate the relationship between domain-specific moderate-to-vigorous-intensity PA (MVPA) and these inflammatory biomarkers among US adults.

Methods: Participants from the US National Health and Nutrition Examination Survey (NHANES) (2007–2018) were included in this study. The Global Physical Activity Questionnaire was used to assess self-reported MVPA. MVPA was categorized into three domains, including occupation-related MVPA (O-MVPA), transportation-related MVPA (T-MVPA), and leisure-time-related MVPA (LT-MVPA). SII, SIRI, and NLR were derived from the complete blood count results obtained at the NHANES Mobile Examination Centers (MEC). Weighted multivariable linear regression and propensity score matching (PSM) were used to examine the relationship between domain-specific MVPA and inflammatory biomarkers. Additionally, stratified and mediation analyses were performed to assess potential effect modifications and mediators in this association.

Results: The study included a total of 29,072 participants. Following PSM, weighted multivariable linear regression indicated a negative association between LT-MVPA meeting PA guidelines ( ≥ 150 min/week) and circulating inflammatory biomarkers (β = −36, 95% confidence interval [CI]: −47 to −25, p  < 0.001 for SII; β = −0.09, 95% CI: −0.13 to −0.05, p  < 0.001 for SIRI; β = −0.08, 95% CI: −0.11 to −0.05, p  < 0.001 for NLR, respectively), adjusting for all potential covariates in model 2. Participants engaging in sufficient T-MVPA (≥ 150 min/week) also exhibited lower SII and SIRI levels (β = −17, 95% CI: −32 to −2.4, p=0.023; β = −0.07, 95% CI: −0.11 to −0.03, p=0.002). Conversely, O-MVPA showed no significant correlation with any inflammatory biomarkers (all p  > 0.05). No significant effect modification was observed in the association between LT-MVPA or T-MVPA and inflammatory biomarkers (SII, SIRI, and NLR). Mediation analysis showed that body mass index (BMI) mediated the relationships between these inflammatory biomarkers and both LT-MVPA and T-MVPA.

Conclusions: The impact of different PA domains on systemic inflammation varies significantly. Given the well-established link between chronic inflammation and diseases such as cardiovascular disease (CVD), diabetes, and metabolic disorders, specific recommendations for PA categories should be provided, particularly targeting individuals with high systemic inflammatory responses.