Biomedical subjects

John W Gardner

Publications and source records attributed to John W Gardner.

11 recordsLinked to original sources

PubMed2006

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.

Adult↗

PubMed2005

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.

Adult↗

PubMed2005

G-induced loss of consciousness: case-control study of 78 G-Locs in the F-15, F-16, and A-10.

INTRODUCTION: This study determined the trends of reported G-induced loss of consciousness (G-LOC) mishaps from 1980--1999, and determined potential risk factors in pilot characteristics; specifically, 30/60/ 90-h and sortie history, total flight hours, total hours in the aircraft, age, height, weight, and BMI. METHODS: Using aircraft malfunction mishaps to reflect a cross-section of USAF pilots, potential risk factors were determined using a case-control method; cases were all G-LOC mishaps and controls were aircraft malfunction mishaps. The data consisted of 2002 mishap pilots in the history of the F-16, F-15, F-15E, and A-10 from 1980-1999. RESULTS: During this time, G-LOCs represented only 2.5% of all mishaps. The mean engagement number for G-LOC mishaps was three at an average of 8 Gs. A poor anti-G straining maneuver was cited in 72% of the mishaps, fatigue and G-suit malfunction in 19%, low G-tolerance at 14%, and 37% were student pilots. Within pilot characteristics, only two factors were found to be statistically significant: the time in the aircraft and pilot age. In the F-16, there was a 3.5 times greater chance of experiencing a G-LOC mishap if the pilot had less than 600 h in the aircraft [3.5 (1.7-7.2, 95%CI)], and a 9.5 times greater chance in the F-15 [9.5 (2.2-41.9, 95%CI)]. There was a 4.5 times greater chance of experiencing a G-LOC mishap if under the age of 30 in the F-16 [4.5 (2.3-8.5, 95% CI)] and a 3 times greater chance in the F-15 [2.8 (1.2-6.8, 95% CI)]. DISCUSSION: Though it is difficult to predict who will experience G-LOC, emphasis on prevention must be concentrated in training and in pilots new to the aircraft.

Aerospace Medicine↗

PubMed2004

Traumatic deaths during U.S. Armed Forces basic training, 1977-2001.

BACKGROUND: A Recruit Mortality Registry, linked to the Department of Defense Medical Mortality Registry, was created to provide comprehensive medical surveillance data for deaths occurring during enlisted basic military training. METHODS: Recruit deaths from 1977 through 2001 were identified and confirmed through redundant sources. Complete demographic, circumstantial, and medical information was sought for each case and recorded on an abstraction form. Mortality rates per 100,000 recruit-years were calculated by using recruit accession data from the Defense Manpower Data Center. RESULTS: There were 276 recruit deaths from 1977 through 2001 and age-specific recruit mortality rates were less than half of same-age U.S. civilian mortality rates. Only 28% (77 of 276) of recruit deaths were classified as traumatic (suicide, unintentional injury, and homicide), in comparison to three quarters in both the overall active duty military population and the U.S. civilian population (ages 15-34 years). The age-adjusted traumatic death rates were highest in the Army (four times higher than the Navy and Air Force, and 80% higher than the Marine Corps). The majority (60%) of traumatic deaths was due to suicide, followed by unintentional injuries (35%), and homicide (5%). The overall age-adjusted traumatic mortality rate was more than triple for men compared with women in all military services (rate ratio=3.9; p=0.01). CONCLUSIONS: There was a lower proportion of traumatic deaths in recruits compared to the overall active duty military population and same-age U.S. civilian population. This finding could be attributed to close supervision, emphasis on safety, and lack of access to alcohol and motor vehicles during recruit training.

Accidents↗

PubMed2004

Nontraumatic deaths during U.S. Armed Forces basic training, 1977-2001.

BACKGROUND: A Recruit Mortality Registry, linked to the Department of Defense Medical Mortality Registry, was created to provide comprehensive medical surveillance data for deaths occurring during enlisted basic military training. METHODS: Recruit deaths from 1977 through 2001 were identified and confirmed through redundant sources. Complete demographic, circumstantial, and medical information was sought for each case and recorded on an abstraction form. Mortality rates per 100,000 recruit-years were calculated by using recruit accession data from the Defense Manpower Data Center. RESULTS: There were 276 recruit deaths from 1977 through 2001 and age-specific recruit mortality rates were less than half of same-age U.S. civilian mortality rates. The majority (72%) of recruit deaths were classified as nontraumatic and 70% of these deaths (139 of 199) were related to exercise. Of the exercise-related deaths, 59 (42%) were cardiac deaths, and heat stress was a primary or contributory cause in at least 46 (33%). Infectious agents accounted for only 49 (25%) of the nontraumatic deaths. Nontraumatic death rates increased with age (rate ratio is 2.5 for 25+ v <25 years; p<0.001). The age- and gender-adjusted nontraumatic death rates were 2.6 times higher for African American than non-African American recruits (p<0.001). CONCLUSIONS: Although recruit mortality rates are lower than the same-age U.S. civilian population, preventive measures focused on reducing heat stress during exercise might be effective in decreasing the high proportion of exercise-related death. The availability of 25 years of comprehensive recruit mortality data will permit the ongoing evaluation of cause-of-death trends, effectiveness of preventive measures, and identification of emerging threats during basic military training.

Adolescent↗

PubMed2004

Predictors of hospitalization in male Marine Corps recruits with exertional heat illness.

Exertional heat illness can have serious consequences and is a common cause of hospitalization during basic military training. The objective of this case-control study was to determine risk factors for hospitalization in male Marine Corps recruits who received medical care for heat illness during their basic military training course at Parris Island, South Carolina. Of 565 heat casualties, 61 (11%) were hospitalized (case subjects) and 504 were treated as outpatients (control subjects). Using univariate and multivariate analyses, demographic, clinical, and laboratory factors were assessed to determine predictors of hospitalization. Nineteen of the 24 analyzed variables were significantly associated with hospitalization. Three clinical variables (disorientation, rectal temperature, systolic blood pressure) and three laboratory variables (serum lactate dehydrogenase, potassium, and creatinine values) were highly predictive for hospitalization in recruits with exertional heat illness. A simple scoring system using these six variables predicted hospitalization with 87% sensitivity, 91% specificity, and a likelihood ratio of 9.7.

Adolescent↗

PubMed2003

Identifying new diseases and their causes: the dilemma of illnesses in Gulf War veterans.

Since the Gulf War, investigation continues of symptoms and illnesses among its veterans. Yet, identifying a specific "Gulf War Syndrome" remains elusive. With new disease entities, causal associations are relatively easily established when the condition is serious, verifiable, and has excess disease rates in specific groups. In common conditions, many excess cases are required to establish association with a specific exposure. Establishing causality in syndromes with variable symptoms is difficult because specific diagnostic algorithms must be established before causal factors can be properly investigated. Searching for an environmental cause is futile in the absence of an operational disease case definition. Common subjective symptoms (without objective physical or laboratory findings) account for over one-half of all medical outpatient visits, yet these symptoms lack an identified physical cause at least one-third of the time. Our medical care system has difficulty dealing with disorders where there is no identified anatomic abnormality or documented metabolic/physiological dysfunction.

Causality↗

PubMed2002

Death by water intoxication.

With recent emphasis on increased water intake during exercise for the prevention of dehydration and exertional heat illness, there has been an increase in cases of hyponatremia related to excessive water intake. This article reviews several recent military cases and three deaths that have occurred as a result of overhydration, with resultant hyponatremia and cerebral edema. All of these cases are associated with more than 5 L (usually 10-20 L) of water intake during a period of a few hours. The importance of maintaining adequate hydration in exertional heat illness prevention cannot be overemphasized, but excessive fluid intake may lead to life-threatening hyponatremia. Current guidelines provide safety by limiting fluid intake during times of heavy sweating to 1 to 1.5 L per hour.

Adolescent↗

PubMed2002

Fatal water intoxication of an Army trainee during urine drug testing.

An Army trainee developed acute water intoxication, hyponatremia, pulmonary edema, and fatal cerebral edema. This is the first report of a fatality related to urine drug testing. This resulted from supervised excessive water ingestion in an attempt to induce a sufficient urine specimen for substance abuse testing. To avoid a similar preventable death in the future, we make several recommendations. These include limiting the volume of ingested fluid to eight ounces every 30 to 45 minutes, not to exceed 40 ounces, and providing a relaxed, reassuring environment when obtaining urine specimens for substance abuse detection.

Adult↗

PubMed2002

Nontraumatic exercise-related deaths in the U.S. military, 1996-1999.

We identified 215 exercise-related deaths in U.S. military personnel on active duty during 1996-1999. The most complete case information was for active duty Army personnel during 1998-1999, providing an exercise-related death rate of 4.3 per 100,000 person-years (41/963,000) and accounting for 6% of Army deaths (14 during physical fitness testing). The cause of death was confirmed by autopsy or clinical data for 85% of the cases. Arteriosclerotic coronary artery disease was the predominant cause of death for those 30 to 58 years of age. For age 17 to 34 years, 50% of deaths were attributable to preexisting heart disease (16% from coronary anomalies), 20% attributable to nontraumatic drowning, and 12% attributable to exertional heat illness, also a potential contributory factor in cardiac deaths. Most exercise-related deaths were related to running (60%), sports (14%), and swimming (13%). Improvements in health promotion, medical management, and stricter exclusion from inappropriate exercise (especially fitness test runs) could reduce these deaths.

Adolescent↗

PubMed2002

Musculoskeletal injuries in an Army airborne population.

To maintain operational readiness, military personnel engage in vigorous physical and training activities that carry risk for injury. A 1-year prospective cohort study, starting April 1996, was conducted at Fort Bragg, North Carolina among 1,965 members of the 82nd Airborne Division to quantify musculoskeletal injuries. Information collected included type of injury, site, circumstances, and resultant limited duty days. These soldiers suffered 508 overuse injuries (including 38 stress fractures), 1,415 traumatic injuries (including 100 fractures), and 101 unclassified injuries. Injury rates were 6.8% per soldier per month for traumatic injury and 2.4% for overuse injury (totaling 1.2 injuries per soldier per year). Injuries resulted in 22,041 limited duty days, averaging 11 days per injury and 13 days per soldier (4.5% of total workdays). Fractures and stress fractures/reactions produced the most days lost per case. Most of these injuries resulted from military-specific activities.

Adult↗