Risk Factors for Medical Discharge From United States Army Basic Combat Training

Transcription

1 MILITARY MEDICINE, 176, 10:1104, 2011 Risk Factors for Medical Discharge From United States Army Basic Combat Training David I. Swedler, MPH * ; Joseph J. Knapik, ScD ; Kelly W. Williams, PhD ; Tyson L. Grier, MS ; Bruce H. Jones, MD ABSTRACT Past studies indicated that overall Basic Combat Training (BCT) attrition (discharge) was associated with various risk factors. BCT has changed considerably since many of these studies were conducted. This study examined Soldiers medically attrited from BCT. Potential attrition risk factor data on recruits ( n = 4,005) were collected from medical records, BCT unit records, and questionnaires. Attrition data from Fort Jackson, South Carolina, showed 203 medical discharges. Cox regression (univariate and multivariate) obtained hazard ratios and 95% confidence intervals for attrition risk factors. Higher attrition risk was associated with female gender. Higher attrition risk for men was associated with cigarette smoking, injury during BCT, and less exercise before BCT. Higher attrition risk for both genders was associated with failure on the initial 2-mile run test and separated or divorced marital status. Attrition risk factors found in this study were similar to those previously identified despite changes in BCT. INTRODUCTION In Fiscal Year 2007, about 1,500, or 4%, of recruits entering U.S. Army Basic Combat Training (BCT) were discharged during BCT. 1 The cost to recruit and medically clear a trainee has been estimated at $22,000 and the cost of BCT at $18, Thus, the monetary losses in Fiscal Year 2007 because of BCT attrition were between $33 and $57 million, depending on when the recruit was discharged. Discharge rates have been increasing over the last few years. 3 Previous studies have shown that medical/physical problems account for many of the discharges within the first 6 months of Army enlistment.4 Several factors have consistently been shown to increase risk for attrition from basic training (BT) in the military services. These include previous tobacco use, 5 9 poor physical fitness,6,10,11 low levels of physical activity before BT, 6,7,9,12 injury during BT, 6,8,10,11,13 and lower education level. 8 10,14 Female gender has generally been shown to be a risk factor for discharge from BT, 8 10,14 yet 1 study showed that men had higher rates of discharge for legal reasons and poor physical performance than women in Air Force BT. 9 Findings on other factors, such as age, 4 ethnicity, 8 10 injury before BT, 8,13 and body mass index (BMI)10,13,15 17 are conflicting with regard to BT attrition. Recent changes in Army entry standards and modifications in the BCT program of instruction suggest that risk factors for BCT attrition should be re-examined. In the middle of the * Center for Injury Research and Policy, Department of Health Policy and Management, Bloomberg School of Public Health, Johns Hopkins University, 624 North Broadway, Room 554, Baltimore, MD Injury Prevention Program, U.S. Army Public Health Command (Provisional), 5158 Blackhawk Road, ATTN: MCHB-TS-DI, Building E-4435, Aberdeen Proving Ground, MD Experimentation and Analysis Element, Basic Combat Training Center of Excellence, Building R-2104, 4325 Jackson Boulevard, Fort Jackson, SC last decade, the maximum age for entry to BCT was raised to 42 years of age 18 and the body fat standards had been relaxed, dependent on enlistees passing a physical fitness test. 19 In 2005, a new physical training program was introduced in BCT. 20 During operational training, more time is spent in field training and more emphasis is placed on counterinsurgency operations. 21,22 In light of these changes, this investigation was designed to examine risk factors for medical discharges from BT as it is currently structured. METHODS Subjects were 2,719 male and 1,286 female recruits entering BCT at Fort Jackson, South Carolina, between March 5, 2007 and May 4, They were briefed on the purposes and risks of the study and provided their voluntary agreement to participate by signing an informed consent statement. The study protocol was approved by the institutional review committee of the Army Medical Research and Development Command. Upon conclusion of informed consent, subjects completed a questionnaire asking about demographics, tobacco use history, physical activity, prior injury, and (for women) menstrual history. Subjects heights and weights were measured during medical inprocessing at the Military Entrance Processing Station and obtained for this study from the Reception Battalion Automated Support System. BMI was calculated as weight/height Gender, race/ethnicity, marital status, education level, and component (Active Army, Reserve, or National Guard) were obtained from the Defense Manpower Data Center. Age was calculated from the date of birth on the questionnaire. Scores from the initial Army Physical Fitness Test (APFT) administered within 1 to 3 days of arrival to BT were obtained from the individual BT units. The APFT consisted of the number of push-ups completed in 2 minutes, maximum number of sit-ups completed in 2 minutes, and a timed 2-mile run. 24 For 1104 MILITARY MEDICINE, Vol. 176, October 2011

2 each event, a point value was given from a standardized ageand gender-adjusted scale. 24 To graduate from BT, recruits needed to score at least 50 points in each of the three events; thus, if a subject had a score of 50 points or greater, he or she was designated as having passed that event; a score of less than 50 points was designated as an event failure. The APFT scores were acquired from the various BT units at the conclusion of training; however, the units need only the final APFT scores (administered later in training), so many had discarded the initial scores. Only about 50% of subjects scores were received. Subject injury status was determined from data from the Defense Medical Surveillance System (DMSS). (This agency is now incorporated into the Armed Forces Health Surveillance Center.) The DMSS regularly obtains data on outpatient encounters at military treatment facilities and those outside the military treatment facilities that were paid for by the Department of Defense. The DMSS provided visit dates and diagnostic codes using the International Classification of Disease, Revision 9 (ICD-9 codes) for all outpatient medical visits during the period each subject was in BT. Subjects were considered to be injured if they had any of the specific series of ICD-9 codes included in the comprehensive injury index, which captures ICD-9 codes related to both overuse injuries/musculoskeletal disorders (e.g., stress fractures, stress reactions, tendonitis, bursitis, fasciitis) and traumatic injuries (e.g., sprains, strains, dislocations, fractures, abrasions, contusions).25 Attrition data were obtained from a local database at Fort Jackson and these were verified against two Army-wide databases: the Resident Individual Training Management System and the Automated Instructional Management System-Personal Computer. Data on each trainee who attrited BT had listed a statute from Army Regulation governing that separation. Medical separations were defined as recruits discharged from active service under Chapter 5-11 (separation of personnel who did not meet procurement fitness standards), Chapter 5-13 (separation because of personality disorder), or Chapter 5-17 (separation for other designated physical or mental conditions) of Army Regulation Statistical analyses were carried out using the Statistical Package for the Social Sciences software (version 16.0; IBM, Chicago, IL). Cox regression was used to examine time to medical discharge and the various potential risk factors with men and women analyzed separately. Time-at-risk was medical discharge date or date censored minus start BT date. (Censoring events included BT graduation or attrition for nonmedical reasons.) Medical discharge was the outcome of interest. Univariate Cox regressions established the relationship between the time-to-medical discharge and each potential risk factor. Variables significant at p < 0.10 level in the univariate analysis were entered into a backward-stepping multivariate Cox regression model. Hazard ratios (HR) and 95% confidence intervals (95% CI) were calculated for each variable relative to a baseline level defined as HR = RESULTS A total of 203 medical separations occurred (5.0% of the cohort). Table I shows the results of the univariate Cox regression. Women had a higher risk of discharge than men (91 men and 112 women were discharged comprising 3.3% and 8.7% of male and female trainees, respectively). Univariate Cox regression in Table I finds that for both men and women, risk of medical discharge was associated with other marital status (divorced, separated, or widowed), smoking in the prior month, failure on the initial APFT push-up or run tests, lower self-rated physical activity, and injury during BCT. For men only, risk of medical discharge was associated with height of 69 to 70 inches, exercising or playing sports less than once per week, running or jogging one or fewer times per week, and prior lower limb injury. For women only, risk of medical discharge was associated with older age, Caucasian ethnicity, BMI 25.0 to 29.9 kg/m 2, smoking more than 10 cigarettes per day, and last pregnancy 13 or more months ago. Table II shows the results of the multivariate Cox regression. Because only 59% of men and 51% of women had scores for the APFT events, the sample of subjects with complete data for all variables in the multivariate models was reduced to 1,593 men and 625 women. Variables independently associated with higher medical discharge risk for men and women included marital status (separated, divorced, or widowed) and failing the initial APFT run. For men, smoking 20 or more days in the month before BT, not exercising or playing sports before BT, and injury during BT increased risk of medical discharge. DISCUSSION Despite recent changes in BCT accession criteria and the program of instruction, this study found that many discharge risk factors were similar to those described previously. These included female gender, cigarette smoking, marital status, poor physical fitness, and less frequent exercise before BCT. Table III compares selected results from this study with previous studies of attrition from BT in various military services. In all these studies, women were at higher risk for discharge than men. The current study found that men and women of other marital status (divorced, widowed, or separated) had a higher rate of medical discharge than single individuals. Few studies have examined the risk of BT discharge for divorced subjects. Georgoulakis et al 27 found a nonsignificant increased risk of discharge for divorced vs. single recruits in BT. In this study, the average age for single subjects (21.6 years) was significantly lower than the mean age of subjects of other marital status (29.7 years) using analysis of variance ( p < 0.001). However, multivariate Cox regression with age and marital status for medical discharge showed that age had a minimal effect on the HR obtained for marital status alone (data not shown). Although research has been done on military service affecting divorce, the authors could not find any prior studies on divorce or separation affecting military service. Further MILITARY MEDICINE, Vol. 176, October

3 TABLE I. Univariate Association of Covariates and Medical Discharge From BT Men Women Category Variable Level N HR (95%CI) N HR (95%CI) Demographic Gender Male Female ( ) Age (years) ( ) ( ) ( ) ( ) ( ) ( ) Race/Ethnicity Caucasian African American ( ) ( ) Hispanic ( ) ( ) Other ( ) ( ) Unknown ( ) 5 High School Graduate Yes No ( ) ( ) Marital Status Single Married ( ) ( ) Other ( ) ( ) Unknown ( ) 0 Physical Height Quartiles (in) M:60 66/W: Characteristics M:67 68/W: ( ) ( ) M:69 70/W: ( ) ( ) M:71 79/W: ( ) ( ) Weight Quartiles (lb) M:96 148/W: M: /W: ( ) ( ) M: /W: ( ) ( ) M: /W: ( ) ( ) BMI (kg/m 2 ) < ( ) ( ) ( ) ( ) Smoking Days Smoked in Last 30 Days Did not smoke ( ) ( ) ( ) ( ) Cigarettes per Day in Last 30 Days None ( ) ( ) ( ) ( ) > ( ) ( ) APFT Push-ups Fail Pass ( ) ( ) Sit-ups Fail Pass ( ) ( ) 2-mile Run Fail Pass ( ) ( ) Prior Physical Activity Times Exercising or Playing Sports, per Week > ( ) ( ) < ( ) ( ) Times Run or Jog, per Week ( ) ( ) Never ( ) ( ) Times Weight Trained, per Week ( ) ( ) ( ) ( ) Self-rated Physical Activity Level Compared to Peers More active Average ( ) ( ) Less active ( ) ( ) Pregnancy/Menstrual History Age at Menarche ( ) ( ) 6 Months Without Menstrual Cycle No Yes ( ) (Continued ) 1106 MILITARY MEDICINE, Vol. 176, October 2011

4 TABLE I. Continued Men Women Category Variable Level N HR (95%CI) N HR (95%CI) Used Birth Control in Past 12 Months No Yes ( ) Last Pregnancy(months) Never ( ) ( ) Injury History Injury During BCT No Yes ( ) ( ) Prior Lower Limb Injury No Yes ( ) ( ) TABLE II. Risk of Medical Discharge From Basic Training, Multivariate Cox Regression Gender Variable Level N HR (95% CI) Men Marital Status Single Married ( ) Other a ( ) Unknown 2 Smoked Cigarettes in Last Month 0 Days Days ( ) 20 Days ( ) Initial APFT Run Score Pass Fail ( ) Frequency Exercised or Played Sports (times per week) 3 or More Days/Week Days/Week or Less ( ) 0 Days/Week ( ) Injury During BCT No Yes ( ) Women Marital Status Single Married ( ) a Other ( ) Initial APFT Run Score Pass Fail ( ) a Other marital status encompasses divorced, separated, or widowed. TABLE III. Risk Factors for Discharge From Basic Training From Prior Studies. Numbers in Table Indicate Relative Discharge Risk in One Group Relative to the Other Study Gender BT Injury Self-Reported Physical Activity Smoking Current Study 2.8 (F/M) 2.2 a (Any Injury, Yes/No) 2.2 b (Average/High) a (Yes/No) Knapik, Army (2001) 1.9 (F/M) 3.4 a (Time-loss Injury, Yes/No) Not Examined Not Examined Talcott, USAF (1999) 1.5 (F/M) Not Examined 1.4 (Continuous) 2.1 (Yes/No) Trone, USMC (2007) Not Examined 4.2 a (Stress Fracture, Yes/No) 3.0 a (Poor/Excellent) Not Examined Booth-Kewley, Navy (2002) 2.2 (F/M) Not Examined Not Examined (Yes/No) F, female; M, male. a Men only. b Women only. research should be done examining how the divorced Soldier copes with his or her service. This study found that older women tended to be at increased risk of discharge compared with younger ones. Previously, Trone et al 13 found that men over 23 years of age were at increased risk compared with those between 19 and 23. In a review of the literature on military discharge, Knapik et al 4 suggested that the relationship between age and discharge may follow a U-shaped curve, with trainees younger than 19 and older than 23 at higher risk than those between 19 and 23. The univariate results for female subjects in this study only found linear relationship of age and discharge risk. Another MILITARY MEDICINE, Vol. 176, October

5 risk for women was a pregnancy 13 or more months before BT. This result was directly related to age: 66% (102/155) of women over 30 had been pregnant 13 or more months previous, whereas only 32% (354/1105) of women under 30 had ever been pregnant (odds ratio: 4.0, 95% CI: ). In the current investigation, individuals who smoked were at increased risk of medical discharge. Smoking is not allowed in BT, 28 so subjects indicated smoking activity up to arrival at Fort Jackson. In consonance with the present study, others have found that prior tobacco use increases BT discharge risk. Blake and Parker 5 found that heavy smokers were more than twice as likely as nonsmokers to be discharged from BCT, whereas Snoddy and Henderson 6 found that the odds of infantry training discharge for smokers was 1.6 times higher than for nonsmokers. Knox 7 reported that recruits who smoked or used smokeless tobacco were 1.4 and 1.2 times more likely to fail Navy BT, respectively, than those who did not use tobacco. Booth-Kewley et al 8 found that smoking was associated with increased risk of behavioral and administrative discharge but did not find a relationship with medical discharge. Tobacco use has negative effects on physical fitness 29,30 and susceptibility to injury and illness Some of these factors could mediate the effect of smoking on BT medical attrition; although for men, smoking, BT injury, and aerobic fitness were all independently associated with medical attrition risk. Although the Departments of Defense and Veterans Administration have tobacco cessation programs (see phc.amedd.army.mil/topics/healthyliving/tc/pages/default. aspx ), we could find no materials for pre-bct tobacco cessation. It is possible that some of the medical attrition could be avoided with increased efforts to get trainees to stop smoking well before they are forced to do so at their BT location. Subjects who scored poorly on the initial APFT were more likely to be medically discharged from BCT than those who did well on the APFT. This is consistent with prior evidence that low fitness, especially low aerobic fitness, increases risk of overall BT attrition. 6,10,11,34,35 Poor performance on the initial APFT push-up test also led to increased risk of medical attrition, as found previously. 6,10 Lower levels of physical fitness on entry to BT may make the physical demands of BT more difficult, possibly leading to higher risks of injury 36 and discharge. One study showed that increasing the physical fitness of new Soldiers before BT can substantially reduce attrition risk 37 ; however, this program was discontinued because of questions over liability. Men who were less physically active before BCT were at increased risk for medical discharge. In addition, women with lower self-rated physical activity were also at increased risk of medical discharge in univariate analysis. The literature has shown that low levels of physical activity before Army, 6,38 Air Force, 9 Navy, 7,12 and Marine Corps 13 BT are associated with higher risk of discharge. Physical activity has favorable effects on the body such as increasing aerobic fitness, muscle strength, and muscular endurance. 39 The higher fitness levels resulting from prior physical activity may reduce discharge risk by more adequately preparing the individual for the physical activity involved in BT. On the other hand, aerobic fitness (2-mile run) and prior physical activity were independent risk factors in the multivariate analysis indicating that these factors separately contributed to attrition risk. Physical activity has many components other than aerobic fitness, which may also reduce medical discharge risk. Unsurprisingly, we found that men and women who experienced an injury during BT were at increased risk for medical discharge. This is in concordance with previous findings on BT discharge and time-loss injury, 10 lower limb injury, 11 and stress fracture. 13 Univariate analysis also showed that men with prior lower limb injury were at increased risk for medical discharge and prior lower limb injury was the last variable removed from the backward-stepping multivariate model ( p = 0.12). Studies of Navy 8 and Marine Corps 13 BT found that prior injury was a risk for discharge in multivariate analysis. Injuries during BT may be exacerbated by prior injuries, or prior injuries may be a marker of higher susceptibility to BT-related injury. Despite many risk factors for BT discharge also being associated with military training injury, 10 injury was still a significant risk factor for medical discharge. Two additional variables were significant risk factors for women in univariate analysis. Caucasian women were at increased risk of medical discharge compared with African American and Hispanic women, a result often reported in the prior literature. 9,10,13,14 Talcott et al 9 hypothesized that Caucasians may see military service as a temporary job, whereas minorities might see it as a career because of fewer options outside the military. Finally, women who had a BMI between 25.0 and 29.9 kg/m 2 (overweight) 40 were at increased risk for medical discharge compared with subjects of normal weight (BMI 25.0) 40 ; however, this study found no difference in medical discharge risk for normal weight and obese (BMI 30) 40 subjects. Although multiple studies have shown increased BMI as a risk for BT discharge, 10,16,17 no consistent relationship has been shown between overweight/obesity and discharge. Similar to the results shown here, a study of Marine Corps BT found subjects with the lowest BMIs to have higher risk of discharge compared with those in the middle and upper BMI categories. 13 Although BMI correlates well with body fat percentage, using it in a physically fit population such as the military might make it less accurate surrogate measure. 41 A main limitation of this study was the poor response rate for the APFT scores. Scores were obtained by physically going training battalion-to-training battalion and requesting the initial APFT scores for all study subjects in a given battalion. Although we were authorized to get them, the battalions were not required to keep the initial scores, thus many simply did not have them. This severely limited our power for multivariate analysis. Although we obtained some data on the final disposition of each injury from the DMSS, we were unable to use these data as a surrogate for injury severity, i.e., more limited 1108 MILITARY MEDICINE, Vol. 176, October 2011

6 duty days designating a more severe injury vs. one where the trainee is immediately returned to his or her training unit after seeing a medic. A qualitative analysis might prove useful here in the future in teasing out the nuances of injury location, severity, and disposition affecting medical discharge. CONCLUSIONS In addition to confirming many known risk factors for medical discharge from BCT, this study found that divorced/widowed/ separated marital status increased male trainees risk of medical discharge. Some of these risk factors (such as smoking history and physical fitness level before arrival at BT) could be modified. To reduce the cost because of medical attrition, the Army (and Department of Defense) might consider encouraging enlistees to undertake programs acclimating them to the physically demanding environment well before they arrive at BT. ACKNOWLEDGMENTS We would like to thank Dr. Steven Bullock, CPT Mark Lester, Nakia Clemmons, Jason Brown, Salima Darakjy, and Carol Pace for assistance in data collection. Claudia Coleman assisted in obtaining reference material. Anita Spiess edited the manuscript. This research was supported in part by an appointment to the Student Research Participation Program at the U.S. Army Center for Health Promotion and Preventive Medicine (USACHPPM) administered by the Oak Ridge Institute for Science and Education through an interagency agreement with the U.S. Department of Energy and USACHPPM. This study was also funded by U.S. Defense Safety Oversight Council, Military Physical Training Task Force Grant. REFERENCES 1. ATTRS. Training Discharge Report. Fort Monroe, VA, Army Training and Doctrine Command, Thomas J : Information Paper. Subject: Cost of a New Recruit. Fort Monroe, VA, USAAC, 2008, p2. 3. Williams K : Attrition Trends. 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