Glucose Levels as a Biomarker for Stress in Firefighters

High morbidity conditions like suicide, cardiovascular disease, and diabetes occur at higher rates for firefighters than in other professions. Despite decades of awareness and targeted efforts to address these problems, firefighters continue to suffer from these conditions at high rates. Stress is a known contributor to these diseases in all populations, and firefighters are exposed to extremely high levels of occupational stress over a 20-30-year career. This problem is commonly approached by focusing research and interventions on the conditions themselves, but an important root cause remains understudied: activation of the sympathetic nervous system (SNS) during emergency response. This activation occurs frequently throughout a firefighter's shift and can be studied by using blood glucose levels as a surrogate marker for SNS activation. The information obtained would offer a significant perspective shift to research and intervention efforts that support firefighter health by shedding new light on SNS activation as a co-morbidity for these conditions. It would also support firefighters in managing their health by providing a new way to quantify stress exposure.

During SNS activation, the liver releases glycogen to increase blood glucose levels, fueling muscles and organs needed in a fight-or-flight response. This response is activated when firefighters are called to emergency scenes by the station alarm. The investigators will equip firefighters with continuous glucose monitors during their shifts and measure changes in serum glucose levels every minute. The hypothesis is that SNS activation will occur during emergency dispatch, resulting in increased blood glucose levels. A secondary hypothesis is that the magnitude of the glucose response will vary based on the self-reported emotional response to the call. Observing the relationship between glucose levels and SNS activation will provide a new perspective on the underlying causes of firefighter health conditions.

Aim 1: Test the hypothesis that glucose levels will increase after emergency dispatch.

Continuous glucose data will be collected every minute, allowing for the comparison of glucose levels before and after a station alarm. If the SNS is activated by a station alarm, an increase in blood glucose levels is anticipated. This information would provide insights into the frequency and magnitude of SNS activation during emergency response. This hypothesis will also generate data on variables that will be used to develop hypotheses for a subsequent study with a larger population. These variables include sleep, diet, and perceived stress. SNS activation is known to have negative health effects that contribute to chronic health problems, for which firefighters are already at elevated risk. Observing the frequency and magnitude of this nervous system response will identify an important contributor to chronic health risks for firefighters.

Aim 2: Test the hypothesis that perceived stress affects glucose levels during emergency dispatch.

Being dispatched to an emergency incident evokes an emotional and stress response that varies for each responder. The limbic system regulates emotional and stress responses, and dysregulation of this system is known to contribute to behavioral conditions. Study participants will report their perceived stress levels for each call they respond to, allowing for a comparison between perceived stress and the magnitude of glucose changes. Participants will identify the three most stressful calls during their shift and the three most stressful events during their days off. These self-reported stressful events will be used as comparison points between on-shift and off-shift stress responses. Observing the relationship between SNS activation and perceived emotional stress exposure will provide a new perspective on emotional stress experiences and help firefighters identify periods of heightened need for supportive resources.

This pilot study will generate data to inform hypotheses for a future large-scale study that may provide new directions for studying and treating chronic health conditions in firefighters. Firefighters are exposed to multiple risk factors while responding to emergency calls, increasing their likelihood of developing chronic health conditions. This study will highlight a new risk factor, enabling fire administrations, governing agencies, and firefighters to take appropriate mitigation measures. Recognizing SNS activation as a co-morbidity would support the development of new, potentially life-saving interventions and foster a cultural shift in how firefighters manage their physical and behavioral health.