Subclinical Cardiac Dysfunction is Associated with Reduced Cardiorespiratory Fitness and Cardiometabolic Risk Factors in Firefighters

Denise L. Smith; Elliot L. Graham; Julie A. Douglas;  Kepra Jack; Michael J. Conner;
Ross Arena; Sundeep Chaudhry;

The American Journal of Medicine (2022) 000:1−9

BACKGROUND: Past studies have documented the ability of cardiopulmonary exercise testing to detect cardiac
dysfunction in symptomatic patients with coronary artery disease. Firefighters are at high risk for
work-related cardiac events. This observational study investigated the association of subclinical cardiac
dysfunction detected by cardiopulmonary exercise testing with modifiable cardiometabolic risk factors in
asymptomatic firefighters.
METHODS: As part of mandatory firefighter medical evaluations, study subjects were assessed at 2 occupational
health clinics serving 21 different fire departments. Mixed effects logistic regression analyses were
used to estimate odds ratios (ORs) and account for clustering by fire department.
RESULTS: Of the 967 male firefighters (ages 20-60 years; 84% non-Hispanic white; 14% on cardiovascular
medications), nearly two-thirds (63%) had cardiac dysfunction despite having normal predicted cardiorespiratory
fitness (median peak VO2 = 102%). In unadjusted analyses, cardiac dysfunction was significantly
associated with advanced age, obesity, diastolic hypertension, high triglycerides, low high-density lipoprotein
(HDL) cholesterol, and reduced cardiorespiratory fitness (all P values < .05). After adjusting for age
and ethnicity, the odds of having cardiac dysfunction were approximately one-third higher among firefighters
with obesity and diastolic hypertension (OR = 1.39, 95% confidence interval [CI] = 1.03-1.87 and
OR = 1.36, 95% CI = 1.03-1.80) and more than 5 times higher among firefighters with reduced cardiorespiratory
fitness (OR = 5.41, 95% CI = 3.29-8.90).
CONCLUSION: Subclinical cardiac dysfunction detected by cardiopulmonary exercise testing is a common
finding in career firefighters and is associated with substantially reduced cardiorespiratory fitness and cardiometabolic risk factors. These individuals should be targeted for aggressive risk factor modification to
increase cardiorespiratory fitness as part of an outpatient prevention strategy to improve health and safety.