Introduction

When firefighters work in the heat they experience changes in immunity and inflammation, possibly increasing the risk of cardiovascular events. However, a risk profile for individuals regarding these changes is largely unknown. This study aimed to establish whether differences in body composition and fitness affect of immune and inflammatory changes of firefighters following work in a hot environment.

Methods

Forty-five urban firefighters (42 male, 3 female) completed a work task in the heat (100 ± 5°C) consisting of two 20-min periods separated by a 10-min passive recovery. Blood was collected at 4 time points (pre and post-work, post+1hr and post+24hrs) during heat testing. Body-fat (BF), lean-mass (LM) and BMI were assessed prior to heat testing using DEXA scans. Aerobic fitness (VO₂) was assessed via the Bruce treadmill protocol. Participants were separated into groups based on these measures (Low, Mod, High). Differences in white blood cells (WBC), and inflammatory markers (TNFα and LPS) were then compared based on groups.

Results

Participants with higher levels of BF had significantly elevated levels of WBC (p=0.01) and TNFα (p=0.03) at the four time points compared with the low groups. Further, LPS was affected by differences in LM alone with the high LM group demonstrating lower values than the low (p=0.04). Neither BMI nor VO₂ groups distinguished levels of any immune or inflammatory variable.

Discussion

Differences in BF and LM may play a predictive role in changes to inflammation in firefighters following work in the heat. Particularly, firefighters demonstrating high BF and/or low LM may experience higher levels of inflammatory activity, which may be predisposing them to a greater risk of a thrombotic event. Focusing on improving body composition, independent of BMI may improve the safety of firefighters by minimising inflammatory responses when they work in the heat.