Firefighters, Heart Disease, and Aspects of Insulin Resistance: The FEMA Firefighter Heart Disease Prevention Study

Acute Effect of Night Shift Work on Endothelial Function with and without Naps: A Scoping Review

We examined the breadth and depth of the current evidence investigating napping/sleeping during night shift work and its impact on non-invasive measures of endothelial function. We used a scoping review study design and searched five databases: Ovid Medline, EMBASE, Ovid APA PsycInfo, Web of Science Core Collection, and EBSCO CINAHL. We limited our search to English language and publications from January 1980 to September 2022. Our reporting adhered to the PRISMA-ScR guidance for scoping reviews. Our search strategy yielded 1949 records (titles and abstracts) after deduplication, of which 36 were retained for full-text review. Five articles were retained, describing three observational and two experimental research studies with a total sample of 110 individuals, which examined the non-invasive indicators of endothelial function in relation to the exposure to night shift work. While there is some evidence of an effect of night shift work on the non-invasive indicators of endothelial function, this evidence is incomplete, limited to a small samples of shift workers, and is mostly restricted to one measurement technique for assessing endothelial function with diverse protocols. In addition, there is no identifiable research investigating the potential benefits of napping during night shift work on non-invasive measures of endothelial function.

Association of the Length of Service of 24/48 Firefighters with the Quality of Their Diet and Selected Anthropometric Parameters

The aim of the study was to examine the association of lengths of service (LS) ≤ 10 years and >10 years in 24/48 shifts with the quality of the observed diet based on the Nutrient Rich Food Index (NRF9.3) and selected anthropometric parameters of 130 firefighters of the State Fire Service (SFS) in Wroclaw, Poland. The study also analysed the individual components of the men's diets required to calculate the NRF9.3 index in both seniority groups. Men with LS > 10 years had statistically significant higher body weight (89.00 kg vs. 81.59 kg), body-fat level (22.80 kg vs. 17.95 kg), waist circumference (96.50 cm vs. 89.00 cm), body-fat percentage (21.94 ± 4.06% vs. 25.00 ± 5.45%), body mass index (BMI) (28.10 kg/m2 vs. 25.40 kg/m2) and waist-hip ratio (WHR) (0.84 0.92 vs. 0.84), compared to the LF ≤ 10 years group. In contrast, the quality of the men's dietary adherence, based on the calculated NRF9.3 index, did not differ between the study groups, and was 662.50 ± 103.1 and 664.78 for the LS ≤ 10 years and LS > 10 years groups, respectively. Based on a statistical analysis using the NRF9.3 diet quality index by tertile (NRF9.3-C), a leading and statistically significant association of LS > 10 years vs. ≤10 years was observed as to most of the anthropometric parameters studied. In contrast, the association of participants' diet quality, as assessed by the NRF9.3 index value, was insignificant for all anthropometric parameters studied.

Potential impact of metabolic syndrome on cognitive function in US firefighters

Objectives

Among US firefighters, sudden cardiac arrest and psychological stress (i.e., PTSD) are the leading cause of on-duty death. Metabolic syndrome (MetSyn) may influence both cardiometabolic and cognitive health. Here, we examined differences in cardiometabolic disease risk factors, cognitive function, and physical fitness in US firefighters with vs. without MetSyn.

Materials and methods

One hundred fourteen male firefighters, aged 20 to 60 years, participated in the study. US firefighters with MetSyn vs. non-MetSyn were divided by AHA/NHLBI criteria. Of them, we performed a paired-match analysis with respect to the age and BMI of firefighters with (n = 18) vs. without MetSyn (n = 18). The cardiometabolic disease risk factors included blood pressure, fasting glucose, blood lipid profiles [HDL-C, triglyceride (TG)], and surrogate markers of insulin resistance [TG/HDL-C, TG glucose index (TyG)]. The cognitive test included a psychomotor vigilance task as a measure of reaction time and a delayed-match-to-sample task (DMS) as a measure of memory, using the computer-based Psychological Experiment Building Language Version 2.0 program. The differences between MetSyn and non-MetSyn groups in US firefighters were analyzed using an independent t-test adjusted for age and BMI. In addition, Spearman correlation and stepwise multiple regression were conducted.

Results

US firefighters with MetSyn exhibited severe insulin resistance estimated by TG/HDL-C and TyG (Cohen's d > 0.8, all p < 0.01) compared with their age- and BMI-matched counterparts without MetSyn. In addition, US firefighters with MetSyn exhibited higher DMS total time and reaction time compared with non-MetSyn (Cohen's d > 0.8, all p < 0.01). In stepwise linear regression, HDL-C predicted DMS total time (β = - 0.440, R² = 0.194, p < 0.05), and TyG (β = 0.432, R² = 0.186, p < 0.05) predicted DMS reaction time.

Conclusion

US firefighters with vs. without MetSyn were predisposed to metabolic risk factors, surrogate markers of insulin resistance, and cognitive function, even when matched for age and BMI, and there was a negative association between metabolic characteristics and cognitive function in US firefighters. The findings of this study suggest that the prevention of MetSyn may be beneficial to supporting firefighters' safety and occupational performance.

Wildfire, Smoke Exposure, Human Health, and Environmental Justice Need to be Integrated into Forest Restoration and Management

PURPOSE OF REVIEW

Increasing wildfire size and severity across the western United States has created an environmental and social crisis that must be approached from a transdisciplinary perspective. Climate change and more than a century of fire exclusion and wildfire suppression have led to contemporary wildfires with more severe environmental impacts and human smoke exposure. Wildfires increase smoke exposure for broad swaths of the US population, though outdoor workers and socially disadvantaged groups with limited adaptive capacity can be disproportionally exposed. Exposure to wildfire smoke is associated with a range of health impacts in children and adults, including exacerbation of existing respiratory diseases such as asthma and chronic obstructive pulmonary disease, worse birth outcomes, and cardiovascular events. Seasonally dry forests in Washington, Oregon, and California can benefit from ecological restoration as a way to adapt forests to climate change and reduce smoke impacts on affected communities.

RECENT FINDINGS

Each wildfire season, large smoke events, and their adverse impacts on human health receive considerable attention from both the public and policymakers. The severity of recent wildfire seasons has state and federal governments outlining budgets and prioritizing policies to combat the worsening crisis. This surging attention provides an opportunity to outline the actions needed now to advance research and practice on conservation, economic, environmental justice, and public health interests, as well as the trade-offs that must be considered. Scientists, planners, foresters and fire managers, fire safety, air quality, and public health practitioners must collaboratively work together. This article is the result of a series of transdisciplinary conversations to find common ground and subsequently provide a holistic view of how forest and fire management intersect with human health through the impacts of smoke and articulate the need for an integrated approach to both planning and practice.

The effect of polycyclic aromatic hydrocarbons on changes in the brain structure of firefighters: An analysis using data from the Firefighters Research on Enhancement of Safety & Health study

Polycyclic aromatic hydrocarbons (PAHs) are formed during incomplete combustion of organic matter, and firefighters are highly exposed to these toxic compounds at fire sites. Exposure to PAHs can cause cognitive decline and neurodegeneration; however, to date, few studies have examined the potential effects of PAH exposure on structural changes in the brain. We aimed to investigate the association between the four types of PAH metabolites and the corresponding changes in neuroimaging markers based on smoking status and hypertension in male firefighters. For this, we utilized the 2-year follow-up data of 301 Korean male firefighters aged over 40 years. The concentrations of four PAH metabolites in urine were measured. Subcortical volume and cortical thickness were estimated using 3 T magnetic resonance imaging of the brain. A generalized linear model was used to investigate the effects of PAHs on changes in the subcortical volume and cortical thickness. We found an association between 1-hydroxyphenathrene (1-OHPHE) and 2-hydroxyfluorene (2-OHF) and changes in several brain regions in all the study participants. Individuals who had never smoked showed significantly thinner frontal (p < 0.001), parietal (p < 0.001), temporal (p < 0.001), and cingulate lobes (p < 0.001) with 1% increase each in the urinary concentration of 1-OHPHE. Hypertension interacted with the concentration of 1-OHPHE to reduce the volume of gray matter and cause cortical thinning in the frontal, parietal, and temporal lobes. Exposure to PAHs may reduce cortical thickness and subcortical volume, which are definitive markers of neurodegeneration. Notably, hypertension can accelerate the degenerative effects of PAHs.

Relationship Between Posttraumatic Stress Symptoms and Cardiovascular Disease Risk in Firefighters

The impact of occupational stress on first responders has received increased investigative attention in recent years. However, research specifically targeting firefighters and their unique responses to job related stress remains limited. Although cardiovascular disease (CVD) risk has been recognized in firefighters, behavioral and psychological contributions (e.g., posttraumatic stress) have not been adequately examined. The purpose of this study was to: (1) examine the relationship between posttraumatic stress symptoms and CVD risk in firefighters, (2) assess the effects of service time on the relationship, and (3) increase understanding of the manifestations of stress in this population. Participants were 87 firefighters from Special Operations teams. Self-report measures of posttraumatic stress symptoms, health, and length of service were administered. Data from annual physical examinations provided information regarding CVD risk (weight, height, blood pressure, cholesterol, smoking, physical exercise). Results indicated significant relationships between posttraumatic stress symptomatology and current smoking status, triglyceride levels, and the number of CVD risk factors. Findings suggest that the presence of posttraumatic stress symptoms may influence overall CVD risk and may not be moderated by years of fire service. Implications for behavioral interventions with firefighters are discussed. Suggestions for future research in this area are offered.

Relationship Between Various Coronary Artery Disease Risk Factors in Firefighters

OBJECTIVE

To determine the correlation between the various coronary artery disease risk factors in firefighters.

METHODS

The study used a quantitative, cross-sectional, and correlational study design. A total of 124 full-time firefighters were conveniently recruited to participate. Research procedures were based on the ACSM guidelines.

RESULTS

Significances were found between age and body mass index (BMI) (r = 0.42, P < 0.001), age and waist circumference (WC) (r = 0.52, P < 0.001), BMI and WC (r = 0.88, P < 0.001), BMI and diastolic blood pressure (DBP) (r = 0.48, P < 0.001), between WC and DBP (r = 0.48, P < 0.001) and between gender and cigarette smoking (χ2[1] = 5.66, P = 0.017).

CONCLUSION

There were significant strong relationships between BMI, SBP, DBP, dyslipidemia, and increasing age, especially in male firefighters. Reducing key risk factors should be emphasized.

A 28-Day Carbohydrate-Restricted Diet Improves Markers of Cardiovascular Disease in Professional Firefighters

Waldman, HS, Smith, JW, Lamberth, J, Fountain, BJ, Bloomer, RJ, Butawan, MB, and McAllister, MJ. A 28-day carbohydrate-restricted diet improves markers of cardiovascular disease in professional firefighters. J Strength Cond Res 34(10): 2785-2792, 2020-This study compared the effects of a 4-week, nonketogenic, carbohydrate-restricted (<25% of calories) diet (CRD) on markers of inflammation and oxidative stress in professional firefighters (FF). Subjects (n = 15) reported to the laboratory for 2 sessions (i.e., baseline and post-CRD) where blood was drawn from an antecubital vein after a 10-hour overnight fast. Dependent variables measured at baseline and post-CRD included adiponectin, insulin, human growth hormone, cortisol, C-reactive protein, albumin, lipids, glucose, amylase, creatine kinase, malondialdehyde (MDA), advance oxidation protein products (AOPP), total nitrate + nitrite, and soluble intracellular adhesion molecule-1. Compared with baseline, the CRD resulted in dramatic improvements to subjects' cardiometabolic profiles, including decreases in AOPP (51.3 ± 27.3 vs. 32.9 ± 7.9 ng·ml), MDA (1.6 ± 0.6 vs. 1.1 ± 0.5 µmol·L), and triglycerides (84.4 ± 34.4 vs. 64.2 ± 14.4 mg·dl), respectively. In addition, the CRD increased total cholesterol (151.5 ± 23.0 vs. 167.7 ± 38.2 mg·dl) and high-density lipoprotein cholesterol (46.3 ± 12.7 vs. 50.6 ± 15.5 mg·dl), but no differences were found with low-density lipoprotein cholesterol. Overall, our results show a 4-week CRD can favorably improve some markers of cardiovascular health in male FF.

Cardiovascular Risk Factor Reduction in First Responders Resulting From an Individualized Lifestyle and Blood Test Program: A Randomized Controlled Trial

OBJECTIVE

We tested the hypothesis that a lifestyle program would improve risk factors linked to cardiovascular disease (CVD) in first responders.

METHODS

A 1-year cluster-randomized controlled clinical trial in 10 cities. Participants were 175 first responders, with increased waist circumference and/or low levels of large (α1) high-density lipoprotein (HDL) particles. The intervention group received personalized online tools and access to telephonic coaching sessions.

RESULTS

At 1 year the intervention significantly reduced body weight (P = 0.004) and waist circumference (P = 0.002), increased α1 HDL (P = 0.01), and decreased triglyceride (P = 0.005) and insulin concentrations (P = 0.03). Program adherence was associated with weight loss (P = 0.0005) and increases in α1 HDL (P = 0.03).

CONCLUSIONS

In first responders, a personalized lifestyle intervention significantly improved CVD risk factors in proportion to program adherence. Changes in large HDL particles were more sensitive indicators of lifestyle changes than HDL-cholesterol measurement.

CLINICAL TRIAL REGISTRATION NUMBER

ClinicalTrials.gov: NCT03322046.

Time-restricted feeding for the prevention of cardiometabolic diseases in high-stress occupations: a mechanistic review

Factors such as shift work, poor diet, lack of physical activity, and irregular sleep patterns put men and women employed in high-stress occupations (e.g., firefighters, police officers) at risk for cardiometabolic diseases. Time-restricted feeding (TRF) is a new approach to combatting many of these diseases; it places an emphasis on when meals are consumed, rather than calorie content. By only manipulating the eating "window," and without changing the food composition of the diet, research in rodent models has shown promising results that have health implications in people, such as obesity prevention, improved insulin sensitivity, and decreased oxidative stress, inflammation, and cholesterol synthesis. Human trials remain limited and the current data are mixed with regard to TRF and improving health. Present findings suggest the timing of the feeding-fasting window, with feeding taking place in the waking hours and fasting in the evening hours, might offer the greatest benefit for improving cardiometabolic markers. Although additional human trials are needed, TRF might reset and synchronize metabolic "clocks" found throughout the body that are disturbed with obesity, shift work, and frequent eating. Therefore, TRF might offer an effective feeding-fasting paradigm with significant clinical implications for the management and treatment of cardiometabolic diseases observed in individuals in high-stress occupations in the United States and in the US population in general. This review outlines the current rodent and human evidence in these areas and the efficacy of TRF for improving human health.

A 28-Day Carbohydrate-Restricted Diet Improves Markers of Cardiometabolic Health and Performance in Professional Firefighters

Waldman, HS, Smith, JW, Lamberth, J, Fountain, BJ, and McAllister, MJ. A 28-day carbohydrate-restricted diet improves markers of cardiometabolic health and performance in professional firefighters. J Strength Cond Res 33(12): 3284-3294, 2019-We investigated the effects of a 4-week ad-libitum, nonketogenic, carbohydrate-restricted (<25% of calories) diet (CRD) on cardiometabolic and performance markers in firefighters (FF). Subjects (n = 15) completed 9 sessions (trials 1-3 [familiarization], trials 4-6 [baseline], and trials 7-9 [post-CRD]). Following habitual western diet, anthropometric measures were assessed, glucose tolerance measured, and then completed a graded cycling test, maximal Wingate test, and conducted their FF physical performance assessment (FPPA) to measure performance while metabolic variables and perceptual responses were recorded. Subjects then adhered to a CRD for a 4-week duration and returned for repeat testing. Body fat as measured by BodPod, and 7-site skinfold thickness decreased (p < 0.01), and a decrease was observed in blood pressure (BP) (p < 0.01; ∼5 mm Hg) after CRD. There were no differences found for glucose tolerance, but an increase was found for fat oxidation rates (p < 0.01; ∼0.07 g·min) and a decrease in carbohydrate oxidation rates across a range of intensities (p < 0.01; ∼0.24 g·min). Finally, the 2.41-km run and pull-up performance during the FPPA improved (p < 0.01; ∼41 second and 3 repetitions, respectively) and with no differences observed between treatments regarding the Wingate test. To date, this is the first CRD implemented with FF and resulted in decreased fat mass (∼2.4 kg), BP, and improvements to performance on the FPPA while preserving high-intensity exercise. These data suggest that a 28-day CRD can benefit markers of health in professional FF without detriments to occupational performance.

The combined treatment with lentil protein hydrolysate and a mixed training protocol is an efficient lifestyle intervention to manage cardiovascular and renal alterations in obese Zucker rats

PURPOSE

Functional and structural changes in cardiovascular and renal systems resulting from obesity and metabolic syndrome represent a severe risk to human health. Lifestyle interventions such as combining healthy diet with adequate physical exercise protocols are good strategies to manage these pathologies. In this research, the effects of lentil protein hydrolysate administration, combined or not with a mixed training protocol, on insulin resistance, cardiovascular and renal functionality were studied in the obese Zucker rat experimental model.

METHODS

Thirty-two rats (16 lean and 16 obese subdivided in sedentary and trained animals) were administered lentil protein hydrolysate, whereas another 32 subdivided in the same experimental design were administered placebo. The experiment lasted for 8 weeks. At the end of the experimental period, insulin resistance and different parameters of cardiovascular and renal functionality were measured.

RESULTS

The individual or combined interventions with lentil protein hydrolysate and mixed training protocol were efficient at counteracting some of the metabolic, cardiovascular and renal alterations characterizing the obese Zucker rat. Specifically, lentil protein hydrolysate decreased hyperphagia, amplitude of QRS complex, plasma ACE and selectin E expression in aorta, while increasing urinary volume and pH. Exercise showed beneficial actions on HOMA-IR, QRS amplitude, QTc interval, urinary volume, kidney weight and Mn-SOD activity. Interestingly, most of the mentioned benefits of exercise were more consistent when protein hydrolysate was also administered.

CONCLUSION

The interesting synergies between the two interventions assessed qualify them as alternative therapeutic strategies to treat cardiovascular and kidney diseases associated to the metabolic syndrome.

Prevalence of Risk Factors for Coronary Artery Disease in Pennsylvania (USA) Firefighters

INTRODUCTION

Firefighting is a physically demanding profession. Heart disease remains the number one killer of firefighters. Many firefighters have multiple risk factors, putting them at risk for sudden cardiac events. The purpose of this study was to describe the prevalence of risk factors for heart disease in a convenience sample of Pennsylvania (USA) firefighters.

METHODS

A convenience sample of 160 firefighters in western Pennsylvania had height, weight, waist circumference, blood pressure, and body mass index (BMI) assessed, and then were surveyed to measure their knowledge of cardiovascular risk factors. Data analysis included subgroup comparisons of age, BMI, waist circumference, and exercise for their impact on health risks in the study cohort. In particular, the researchers were interested in understanding whether the knowledge of risk was associated with lower measures of risk.

RESULTS

Eighteen firefighters (4%) reported a history of coronary artery disease (including stents/interventions). In this group, 69% to 82% correctly identified age, hypertension (HTN), high cholesterol, smoking, obesity, sedentary lifestyle, and family history as risk factors for coronary artery disease. Fourteen percent were smokers, 41% had HTN, 38% had pre-HTN with only 12% receiving treatment, and 13.5% were treated for high cholesterol. Fifty-eight percent exercised regularly.

CONCLUSIONS

While a majority of firefighters were able to identify risk factors for coronary artery disease, many could not. Eighteen (4%) had a history of coronary artery disease, including interventions. Many had several of the risk factors indicated, which highlights the need for an organized national approach to address the medical screening/evaluation, nutrition, and exercise components of firefighter fitness.

Usefulness of coronary and carotid imaging rather than traditional atherosclerotic risk factors to identify firefighters at increased risk for cardiovascular disease

Cardiovascular disease (CVD) accounts for 45% of deaths in on-duty firefighters, in contrast to 15% of all deaths occurring on conventional jobs. Therefore, with the goal of developing a tailored prevention program, we assessed CVD risk in a cohort of 50 firefighters using imaging and traditional risk factors. Participants were aged ≥40 years without a history of CVD or diabetes. CVD risk was assessed by way of history, physical examination, blood tests, risk scores, coronary artery calcium (CAC), and carotid intima-media thickness (cIMT). Median age was 46 years; 90% of subjects were men, 92% were white, and 30% were former smokers. Only 4% of subjects were hypertensive but 48% were prehypertensive. Only 14% of subjects had a normal body mass index; 38% were overweight, 48% were obese, and 46% had a high waist circumference. Based on fasting glucose ≥100 mg/dl or hemoglobin A1c ≥5.6%, 50% of subjects had prediabetes and 2% had diabetes. Median total cholesterol was 196 mg/dl; median high-sensitivity C-reactive protein was 1.0 mg/L. CAC was detected in 22% of subjects and carotid plaque was detected in 36%. Using standard reference databases, 54% of subjects had cIMT greater than the seventy-fifth percentile; 66% had carotid plaque and/or cIMT greater than the seventy-fifth percentile. Atherogenic lipoprotein markers and risk scores did not differ between firefighters who had subclinical atherosclerosis and those who did not. Traditional CVD risk assessment does not adequately identify at-risk firefighters. In contrast, CAC and cIMT were useful for identifying increased risk and implementing primary prevention. In conclusion, early detection and integration of imaging with traditional risk assessment will be important in preventing premature death and disability among firefighters.

What does it cost to prevent on-duty firefighter cardiac events? A content valid method for calculating costs

Cardiac arrest is a leading cause of mortality among firefighters. We sought to develop a valid method for determining the costs of a workplace prevention program for firefighters. In 2012, we developed a draft framework using human resource accounting and in-depth interviews with experts in the firefighting and insurance industries. The interviews produced a draft cost model with 6 components and 26 subcomponents. In 2013, we randomly sampled 100 fire chiefs out of >7,400 affiliated with the International Association of Fire Chiefs. We used the Content Validity Index (CVI) to identify the content valid components of the draft cost model. This was accomplished by having fire chiefs rate the relevancy of cost components using a 4-point Likert scale (highly relevant to not relevant). We received complete survey data from 65 fire chiefs (65% response rate). We retained 5 components and 21 subcomponents based on CVI scores ≥0.70. The five main components include, (1) investment costs, (2) orientation and training costs, (3) medical and pharmaceutical costs, (4) education and continuing education costs, and (5) maintenance costs. Data from a diverse sample of fire chiefs has produced a content valid method for calculating the cost of a prevention program among firefighters.

Genetic testing for early detection of individuals at risk of coronary heart disease and monitoring response to therapy: challenges and promises

Coronary heart disease (CHD) often presents suddenly with little warning. Traditional risk factors are inadequate to identify the asymptomatic high-risk individuals. Early identification of patients with subclinical coronary artery disease using noninvasive imaging modalities would allow the early adoption of aggressive preventative interventions. Currently, it is impractical to screen the entire population with noninvasive coronary imaging tools. The use of relatively simple and inexpensive genetic markers of increased CHD risk can identify a population subgroup in which benefit of atherosclerotic imaging modalities would be increased despite nominal cost and radiation exposure. Additionally, genetic markers are fixed and need only be measured once in a patient's lifetime, can help guide therapy selection, and may be of utility in family counseling.