Rhabdomyolysis in the US Active Duty Army, 2004-2006.

PURPOSE: Rhabdomyolysis (RM) is a skeletal muscle disorder resulting in severe cellular injury caused by vigorous physical activity and other systemic etiologies. RM is associated with significant morbidity, such as acute renal failure, and can be fatal. RM that occurs in the US Active Duty Army (ADA) results in time lost from training, deployment, and combat. We sought to systemically describe the epidemiology of ADA clinical RM by quantifying RM in terms of absolute numbers, examine rate trends, and identify soldiers at elevated risk. METHODS: We used data from the Total Army Injury and Health Outcomes Database to calculate yearly RM rates in the overall ADA, as well as adjusted RM rates within soldier subpopulations for 2003-2006. RESULTS: During this period, the absolute numbers of clinically diagnosed ADA RM ranged between 382 and 419 cases per year. Annual rates were 7-8 per 10,000, which is 300%-400% higher than the estimated US civilian population (2 per 10,000). In soldiers with a history of a prior heat injury, RM rates climbed to 52-86 per 10,000, a 7- to 11-fold increase. Increased RM rates were seen in soldiers who are male, African American, younger, less educated, and with a shorter length of service. Approximately 8% of yearly ADA RM cases resulted in acute renal failure, an estimate lower than that for the US civilian population. CONCLUSIONS: Our findings suggest that rates of RM are higher in the ADA than in the US civilian population. Rates remained fairly stable; however, relative to other ADA soldiers, those with prior heat injury, who are African American, or who have a length of service of less than 90 d are at the highest risk for RM development.

Rates of ankle and foot injuries in active-duty U.S. Army soldiers, 2000-2006.

Ankle and foot injuries (AFI) are a major cause of Active-Duty Army (ADA) soldiers' time lost from training and combat operations. We used the Total Army Injury and Health Outcomes Database to compute the rates of AFI to identify high-risk ADA groups for the years 2000-2006. During this time, 16% of soldiers were clinically seen at least once for an AFI. Yearly, 60% to 70% of ADA soldiers with AFI had an ankle sprain/strain, and ankle sprain/strain had the highest 7-year rate of all AFIs (103 per 1,000). From 2000 to 2006, all AFI rates declined; however, enlisted male soldiers < or = 30 years of age without an advanced degree were at highest risk. A history of an AFI in the previous 2 years increased AFI rates by 93% to 160%. Our findings provide preliminary evidence for identifying specific ADA groups at high risk of AFI; these groups should be targeted for preventive interventions.

Prior heat illness hospitalization and risk of early death.

Previous evidence suggests that severe heat illness may cause permanent acute damage to the heart, kidneys, and liver, which may possibly lead to chronic and even fatal disorders. We investigated whether individuals who had been hospitalized for severe heat illness were at increased risk of cause-specific and total mortality. A cohort mortality study was conducted of male and female US Army personnel hospitalized for heat illness (HI) from 1971 to 2000 using appendicitis (APX) as the reference. Hospitalization records were acquired from the Total Army Injury and Health Outcomes Database (TAIHOD) for 3971 cases of HI and 17,233 APX reference cases. Subject vital status was established through the National Death Index. HI cases had a 40% increased risk of all-cause mortality compared to APX cases. Further examining cause-specific deaths, male cases of HI were at an increased rate of death from cardiovascular disease (CVD) (rate ratio (RR)=1.71, 95% confidence interval (CI): 1.01, 2.89) and ischemic heart disease (IHD) (RR=2.23, 95% CI: 1.02, 4.90) compared to APX reference cases. Our findings provide preliminary evidence for increased risk of mortality among those who have experienced prior hospitalization for heat illness.

Risk factors for recruit exertional heat illness by gender and training period.

INTRODUCTION: Exertional heat illness (EHI) is a recurrent problem for both male and female recruits during basic military training. A matched case control study investigated the effects of fitness and conditioning on EHI risk among Marine Corps recruits during 12 wk of basic training at Marine Corps Recruit Depot, Parris Island, SC. METHODS: Physical fitness and anthropometric measurements at entrance were acquired for 627 EHI cases that occurred during the period 1988-1996 and for 1802 controls drawn from the same training platoons. Conditional logistic regression was used to estimate EHI risk. RESULTS: Slower physical fitness test run times during processing week strongly predicted risk for subsequent EHI in both male and female recruits. A 9% increase in risk for EHI associated with body mass index (BMI = kg x m(-2); weight/height2) was found in male recruits, while BMI was not associated with risk among female recruits. BMI and initial run time were important predictors for EHI in early training, while in late training the initial BMI was no longer as important a risk factor and improvements in fitness reduced risk. CONCLUSION: Tables of estimated absolute risks categorized by BMI and VO2max are provided as a guide for identifying recruits who are at high risk for developing EHI during training.

The effects of continuous hot weather training on risk of exertional heat illness.

PURPOSE: To determine whether cumulative daily average wet-bulb globe temperature (WBGT) index, over one or two preceding days, is a better measure for predicting cases of exertional heat illness (EHI) than current daily average WBGT, which is the standard heat index used by the Marine Corps; and to identify the most accurate index of heat stress to prevent and predict future cases of EHI. METHODS: A case-crossover study was conducted in male and female Marine Corps recruits in basic training at Marine Corps Recruit Depot, Parris Island, SC. Weather measurements were obtained for 2069 cases of EHI during 1979-1997 and for randomly selected control periods before and after each EHI episode. RESULTS: The risk of EHI increased with WBGT (OR = 1.11 degrees F(-1); 95% CI, 1.10-1.13). EHI risk was associated not only with the WBGT at the time of the event (OR = 1.10 degrees F(-1); 95% CI, 1.08-1.11) but with the previous day's average WBGT as well (OR = 1.03 degrees F(-1); 95% CI, 1.02-1.05). Alternative combinations of WBGT components were identified that better predicted EHI risk. CONCLUSION: Our results provide evidence for a cumulative effect of previous day's heat exposure on EHI risk in these Marine Corps recruits. A simple index for use in predicting EHI risk is proposed that includes the dry-bulb temperature and the relative humidity.