Total Energy Intake and Self-Selected Macronutrient Distribution During Wildland Fire Suppression

Wildland Firefighter Work History and Clinical Indicators of Cardiovascular Health

OBJECTIVE

To determine the association between the occupational history as a wildland firefighter (WFF) and clinical indicators of cardiovascular health.

METHODS

Among 2862 WFFs, we evaluated associations between the number of total days assigned on fire and high-risk categories of three clinically measured cardiovascular indicators.

RESULTS

Almost one-third (32%) of WFFs had one or more clinical measures that would place them in high-risk categories for body mass index, blood pressure, and total cholesterol. WFF work history was associated with some of these measures: odds ratio (and 95% confidence interval) for highest versus lowest tertile of days on fire were 1.4 (1.2, 1.8) and 1.2 (1.0, 1.5) for high-risk categories of body mass index and cholesterol, respectively.

CONCLUSION

More frequent screening and targeted health promotion programs for WFFs are warranted to increase awareness of cardiovascular risk and prevention strategies.

The wildland firefighter exposure and health effect (WFFEHE) study: cohort characteristics and health behavior changes in context

OBJECTIVES

Work is an under-recognized social determinant of health. There is limited research describing US wildland firefighter (WFF) workforce demographics or how to work associates with WFF health behaviors. In this study researchers characterized a WFF cohort and tested hypotheses that WFFs used tobacco, alcohol, and sugar-sweetened beverages (SSBs) differently over the course of the fire season and that different fire crews may exhibit different behavior patterns.

METHODS

Researchers collected data in the field with 6 WFF crews during 2 consecutive fire seasons (2018 and 2019). WFF crews completed questionnaires before and after each season. WFFs with an initial preseason questionnaire and at least 1 follow-up questionnaire were included (n = 138). Descriptive statistics summarized WFFs' baseline demographic, employment, and health characteristics. Linear mixed models were used to test for changes in WFFs' substance use over time and assess crew-level differences. A meta-analysis of WFF longitudinal studies' population characteristics was attempted to contextualize baseline findings.

RESULTS

WFFs were predominately male, less than 35 yr of age, non-Hispanic White, and had healthy weight. Smokeless tobacco use and binge drinking were prevalent in this cohort (52% and 78%, respectively, among respondents). Longitudinal analyses revealed that during the fire season WFFs' use of tobacco and SSBs increased and the number of days they consumed alcohol decreased. Crew-level associations varied by substance. The meta-analysis was not completed due to cross-study heterogeneity and inconsistent reporting.

DISCUSSION

WFF agencies can promote evidence-based substance use prevention and management programs and modify working conditions that may influence WFF stress or substance use.

Using Focus Groups to Identify Nutrition Education Needs and Implementation Strategies for the Wildland Firefighter

OBJECTIVES

The aims of the study are to describe the current state, identify topics of importance, and suggest implementation strategies for tailored nutrition education for the WLFFs.

METHODS

Focus groups were conducted and survey data was collected to gather qualitative and quantitative data from a sample of WLFFs. Constant comparative strategy was used to generate themes from transcripts.

RESULTS

Wildland firefighters showed interest in early-introduced, multimodal, and specific nutrition education tailored to the demands of the WLFF.

CONCLUSIONS

Study findings provide nutrition topics of interest and importance to WLFFs and may be used to develop educational materials.

Wildland Firefighter Critical Training Elicits Positive Adaptations to Markers of Cardiovascular and Metabolic Health

INTRODUCTION

The purpose of this study was to identify physiologic changes in body composition and resting metabolic markers of health across 2 wk of critical training (CT) in wildland firefighters (WLFFs).

METHODS

Twenty-two male and 3 female participants were recruited from 2 hotshot crews across the western United States prior to the 2022 fire season and monitored over their 80-h CT. Body weight (BW) and skinfolds were recorded before and after CT to estimate body fat (BF) and lean body weight (LBW). Blood was analyzed for changes in hematocrit, hemoglobin, plasma volume, and resting values of a lipid and metabolic panel.

RESULTS

The high physical demands of CT resulted in improvements in total cholesterol (-19.3 mg/dL, P<0.001), triglycerides (-34.4 mg/dL, P<0.001), low-density lipoprotein cholesterol (-18.1 mg/dL, P<0.001), very-low-density lipoprotein cholesterol (-5.2 mg/dL, P<0.001), high-density lipoprotein cholesterol (+4.0 mg/dL, P=0.002), non-high-density lipoprotein cholesterol (-19.3 mg/dL, P<0.001), and fasting glucose (-4.3 mg/dL, P=0.008) from before CT to after CT. Significant decreases in hemoglobin and hematocrit were also seen (P<0.001) with corresponding increases in estimated plasma volume (+6.1%, P<0.001). These alterations were seen despite maintenance of BW, LBW, and BF. Lower pretraining BF was associated with a greater magnitude of improvements in fasting glucose and cholesterol markers.

CONCLUSIONS

The observed improvements in baseline metabolic and cardiovascular markers along with plasma volume expansion suggest a positive response to the physical stress of WLFF CT. It appears that higher preseason fitness was associated with greater adaptations to the CT stressor.

Use of accelerometers and inertial measurement units to quantify movement of tactical athletes: A systematic review

The dynamic work environments of tactical athletes are difficult to replicate in a laboratory. Accelerometers and inertial measurement units provide a way to characterize movement in the field. This systematic review identified how accelerometers and inertial measurement units are currently being used to quantify movement patterns of tactical athletes. Seven research and military databases were searched, producing 26,228 potential articles with 78 articles included in this review. The articles studied military personnel (73.1%), firefighters (19.2%), paramedics (3.8%), and law enforcement officers (3.8%). Accelerometers were the most used type of sensor, and physical activity was the primarily reported outcome variable. Seventy of the studies had fair or poor quality. Research on firefighters, emergency medical services, and law enforcement officers was limited. Future research should strive to make quantified movement data more accessible and user-friendly for non-research personnel, thereby prompting increased use in tactical athlete groups, especially first responder agencies.

Working hours, sleep, and fatigue in the public safety sector: A scoping review of the research

BACKGROUND

The public safety sector includes law enforcement officers (LEO), corrections officers (CO), firefighter service (FF), wildland firefighting (WFF), and emergency medical services (EMS), as defined in the National Occupational Research Agenda (NORA) of the National Institute for Occupational Safety and Health (NIOSH). Across these occupations, shiftwork, long-duration shifts, and excessive overtime are common. Our objective was to identify research gaps related to working hours, sleep, and fatigue among these workers.

METHODS

We used a scoping review study design that included searches of MEDLINE, Embase, CAB Abstracts, Global Health, PsychInfo, CINAHL, Scopus, Academic Search Complete, Agricultural and Environmental Science Collection, ProQuest Central, Cochrane Library, Safety Lit, Homeland Security Digital Library, and Sociological Abstracts using a range of occupational search terms and terms related to working hours, sleep, and fatigue.

RESULTS

Out of 3415 articles returned from our database search, 202 met all inclusion criteria. Six common outcomes related to working hours, sleep, and fatigue emerged: sleep, fatigue, work performance, injury, psychosocial stress, and chronic disease. Nearly two-thirds (59%, n = 120) of the studies were observational, of which 64% (n = 77) were cross sectional and 9% were (n = 11) longitudinal; 14% (n = 30) of the studies were reviews; and 19% (n = 39) were experimental or quasi-experimental studies. Only 25 of the 202 articles described mitigation strategies or interventions. FFs, LEOs, EMS, and WFFs were the most studied, followed by COs.

CONCLUSIONS

In general, more longitudinal and experimental studies are needed to enrich the knowledge base on the consequences of long working hours, poor sleep, and fatigue in the public safety sector. Few experimental studies have tested novel approaches to fatigue mitigation in diverse sectors of public safety. This gap in research limits the decisions that may be made by employers to address fatigue as a threat to public-safety worker health and safety.

The Relationship Between Dietary Intake and Dietary-Focused Lifestyle Interventions on Risk Factors Associated with Cardiovascular Disease in Firefighters

PURPOSE OF REVIEW

Cardiovascular disease (CVD) is the leading cause of death to on-duty firefighters and is a substantial health concern. Preventative measures, including dietary interventions, may improve CVD in firefighters. The purpose of this review is to examine the literature on the relationship between dietary intake, dietary lifestyle interventions, and risk of CVD in firefighters.

RECENT FINDINGS

Existing evidence, albeit limited, suggests that firefighters do not meet dietary guidelines. Lifestyle modifications featuring dietary interventions are effective in improving risk factors associated with CVD in firefighters. Unfortunately, no consistent nutrition-related trend was identified across the retrieved studies and only a limited number of randomized controlled trials have examined the efficacy of lifestyle intervention studies on CVD in firefighters. Although this review suggests dietary lifestyle interventions may facilitate decreases in risk factors associated with CVD in firefighters, current evidence is limited, and additional research is needed.

Health risks and mitigation strategies from occupational exposure to wildland fire: a scoping review

OBJECTIVES

Due to accelerating wildland fire activity, there is mounting urgency to understand, prevent, and mitigate the occupational health impacts associated with wildland fire suppression. The objectives of this review of academic and grey literature were to: 1. Identify the impact of occupational exposure to wildland fires on physical, mental, and emotional health; and 2. Examine the characteristics and effectiveness of prevention, mitigation, or management strategies studied to reduce negative health outcomes associated with occupational exposure to wildland fire.

METHODS

Following established scoping review methods, academic literature as well as government and industry reports were identified by searching seven academic databases and through a targeted grey literature search. 4679 articles were screened using pre-determined eligibility criteria. Data on study characteristics, health outcomes assessed, prevention or mitigation strategies studied, and main findings were extracted from each included document. The results of this scoping review are presented using descriptive tables and a narrative summary to organize key findings.

RESULTS

The final sample was comprised of 100 articles: 76 research articles and 24 grey literature reports. Grey literature focused on acute injuries and fatalities. Health outcomes reported in academic studies focused on respiratory health (n = 14), mental health (n = 16), and inflammation and oxidative stress (n = 12). The identified studies evaluated short-term outcomes measuring changes across a single shift or wildland fire season. Most research was conducted with wildland firefighters and excluded personnel such as aviation crews, contract crews, and incident management teams. Five articles reported direct study of mitigation strategies, focusing on the potential usage of masks, advanced hygiene protocols to reduce exposure, fluid intake to manage hydration and core temperature, and glutamine supplementation to reduce fatigue.

CONCLUSIONS

While broad in scope, the evidence base linking wildland fire exposure to any one health outcome is limited. The lack of long-term evidence on changes in health status or morbidity is a clear evidence gap and there is a need to prioritize research on the mental and physical health impact of occupational exposure to wildland fire.

Nutrient Intake of Wildland Firefighters During Arduous Wildfire Suppression: Macronutrient and Micronutrient Consumption

Wildland firefighters (WLFFs) perform in adverse environments making rapid adjustments to dietary needs. The National Mobile Food Services (NMFS) contract details WLFF dietary provisions on wildfire incidents.

OBJECTIVE

Determine the nutrient content of food and drink provided to and consumed by WLFFs under the NMFS contract.

METHODS

Individual (n = 122) dietary provisions and consumption was recorded during 1 workday. Nutritional analysis of items provided was compared with consumption and the recommended dietary allowance (RDA).

RESULTS

WLFFs consumed significantly (P < 0.05) fewer macronutrients than provided for calories, protein, and fat. Provided and consumed micronutrients were below the RDA for vitamins D and E, magnesium, and manganese.

CONCLUSION

Most dietary recommendations were met by NMFS provisions. Next steps include WLFF nutrition education to improve consumption and contract revisions to meet micronutrient recommendations.

Deterioration of Lipid Metabolism Despite Fitness Improvements in Wildland Firefighters

OBJECTIVE

Determine serum lipid and general health/fitness alterations following a 5-month wildfire suppression season.

METHODS

We recruited 100 wildland firefighters (WLFFs) to a 5-month pre- to post-season observational study. Nude body mass, blood pressure (BP), grip strength, and step-test heart rate (HR) were recorded. Blood samples were collected for lipid panel analysis (total cholesterol, HDL-cholesterol, LDL-cholesterol, VLDL-cholesterol, triglycerides, triglyceride:HDL-cholesterol ratio). Two-tailed dependent t-tests determined statistical significance (p < 0.05).

RESULTS

There were pre- to post-season changes in nude body mass (+2 ± 4%, p = 0.001), systolic BP (-2 ± 10%, p = 0.01), step-test HR (-5 ± 10%, p < 0.001), and all serum lipids (total cholesterol: +5 ± 14%, p = 0.02, HDL-cholesterol: -1 ± 17%, p = 0.04, LDL-cholesterol: +8 ± 22%, p = 0.02, VLDL-cholesterol: +31 ± 49%, p < 0.001, triglycerides: +30 ± 49%, p < 0.001, triglyceride:HDL-cholesterol ratio: +37 ± 58%, p < 0.001). Pre- to post-season diastolic BP (p = 0.12) and grip strength (p = 0.60) remained stable.

CONCLUSIONS

WLFFs demonstrate maladaptive serum lipids and body mass alterations despite subtle aerobic fitness improvements.

Workshift Changes in Hydration Status During Wildfire Suppression

OBJECTIVE

Document wildland firefighters (WLFFs) hydration status during a singular workshift (13.7 ± 1.4 hours).

METHODS

WLFF researchers documented real-time WLFF (n = 71) urine metrics and fluid consumption. Body weight and blood samples (n = 25) were also collected. Two-tailed dependent t tests determined statistical significance (P < 0.05).

RESULTS

Body weight significantly decreased (-0.3 ± 1.1%, P > 0.05). Fluid consumption totaled 6.2 ± 2.3 L including food and 5.0 ± 2.1 L without food. Morning versus afternoon urine frequency (2.6 ± 1.3, 3.1 ± 1.9 voids), urine volume (1.2 ± 0.7, 1.3 ± 0.8 L), urine volume per void (440 ± 157, 397 ± 142 mL), and urine specific gravity (1.010 ± 0.007, 1.010 ± 0.007) were not significantly different (P > 0.05). Pre- to post-workshift serum chloride (103.2 ± 1.9, 101.4 ± 1.7 mM) and blood glucose (5.2 ± 0.4, 4.5 ± 0.7 mM) significantly decreased (P < 0.05), while serum sodium (141.5 ± 2.4, 140.8 ± 2.0 mM) and serum potassium (4.3 ± 0.3, 4.2 ± 0.3 mM) remained stable (P > 0.05).

CONCLUSIONS

WLFFs can ingest fluid and food amounts that maintain workshift euhydration and electrolyte status.

Free-Living Dietary Intake in Tactical Personnel and Implications for Nutrition Practice: A Systematic Review

Tactical personnel (including military, law enforcement, and fire and rescue) are responsible for ensuring national and public safety. Dietary intake is an important consideration to support optimal health and performance. The aims of this systematic review were to: (1) describe the reported free-living dietary intake (energy and macronutrients) of tactical personnel, and (2) describe the practical implications of reported dietary intakes to support the physical and dietary requirements of tactical personnel. A systematic search of databases (MEDLINE, EMBASE, CINAHL and Web of Science) was conducted following the PRISMA guidelines. English and full text research articles were identified and screened against inclusion and exclusion criteria. Demographic and dietary intake data were extracted, tabulated, and synthesized narratively. The quality of the studies was assessed using the Academy of Nutrition and Dietetics Quality Criteria Checklist. Twenty-two studies (15 military, 4 law enforcement, and 2 fire and rescue) were eligible to inform this review. The volume of evidence suggested that tactical personnel met dietary protein and exceeded dietary fat recommendations but failed to meet energy and carbohydrate recommendations. Therefore, practical approaches to support optimized energy, fat and carbohydrate intake in tactical personnel is important.

Evaluation of Environmental Conditions on Self-Selected Work and Heat Stress in Wildland Firefighting

INTRODUCTION

The purpose of this study was to evaluate heat stress occurring in wildfire management activities with variable environmental conditions.

METHODS

Direct observation and real-time wireless physiological monitoring allowed for weather and physiological metrics, including heart rate, core temperature (T_c), skin temperature, and physiological strain index (PSI), of male (n=193) and female (n=28) wildland firefighters (WLFFs) to be recorded during wildfire management activities. Accelerometry data were used to categorize intensity level of activity.

RESULTS

Ambient temperature and relative humidity values were used to compute the heat index (HI; n=3891 h) and divided into quartiles (Q1: 13.3-25.1°C; Q2: 25.2-26.4°C; Q3: 26.5-28.9°C; Q4: 29.0-49.1°C). Activity levels remained relatively constant across all HI quartiles. The percentage of time spent performing moderate/vigorous activities was lowest during the hotter Q4 (Q1: 3%; Q2: 2%; Q3: 2%; Q4: 1%). Heart rate, T_c, PSI, and skin temperature associations with HI varied by resource type. Sixty-one percent of WLFFs (n=134) experienced a T_c ≥38.0°C, and 50% of WLFFs (n=111) experienced a PSI ≥6.0.

CONCLUSIONS

Heat stress was prevalent as WLFFs performed job tasks of varying intensities in all ambient conditions. Spontaneous bouts of arduous labor, duration of work shifts, and other occupation characteristics present the possibility for substantial durations of hyperthermia, although no heat-related injuries occurred in this study. Despite chronic exposure to rugged sloped terrain, load carriage, and environmental conditions, self-regulation and individual attention to managing work:rest appears to be the primary management strategy in mitigating excessive accumulation of body heat in this occupation.

Impact of wildland firefighting on arterial stiffness and cardiorespiratory fitness

The purpose of this study was to assess the effect of wildland firefighting on measures of cardiovascular health. The study was carried out in two parts. Part one assessed relationships between years of wildland firefighting and cardiovascular variables (n = 28). Part two looked at cardiovascular variables pre and post a wildland firefighting season (n = 18). Independent of age, a statistically significant relationship between number of seasons firefighting and VO_2max was found (r²=.140, p=.048). A statistically significant reduction in VO_2max of -4.1 ± 5.7 ml·kg^-1 min^-1 was witnessed following fire season (95%CI=-6.9 to -1.3, p=.048). Year to date hazard pay was significantly correlated with ankle-brachial index (r=-.474, p=.040). Wildland firefighters who reported >640 h of hazard pay had a greater VO_2max reduction than those reporting less hazard pay (-1.7 ± 5.7 ml·kg^-1·min^-1 vs. -7.1 ± 4.3 ml·kg^-1·min^-1, p=.037). Wildland firefighting may negatively impact cardiorespiratory fitness and arterial health.