Ornstein-Uhlenbeck threshold regression for time-to-event data with and without a cure fraction.

In this paper we propose a threshold regression (TR) model for time to event data related to subject health using a latent Ornstein-Uhlenbeck (OU) process that fails once it hits a boundary value for the first time. Baseline covariates are incorporated into the analysis using a log-link function for the initial state of the health process. The model provides clinically meaningful covariate effects and does not require the proportional hazards assumption of the commonly used Cox model. Unlike TR models based on the Wiener process, the OU model allows increments in the health process to depend on previous values and drifts toward a state of equilibrium or homeostasis, which are present in many biological applications. We also extend our model to incorporate a cure rate for applications with improper survival functions, such as time to tumor recurrence in a cancer clinical trial. Our models are applied to overall and relapse-free survival data of melanoma patients undergoing definitive surgery.

Neck injury criteria formulation and injury risk curves for the ejection environment: a pilot study.

BACKGROUND: Helmet mounted displays provide increased pilot capability, but can also increase the risk of injury during ejection. The National Highway Transportation Safety Administration's (NHTSA's) neck injury criteria (Nij) metric is evaluated for understanding the impact of helmet mass on the risk of injury and modified risk curves are developed which are compatible with the needs of the aviation community. METHODS: Existent human subject data collected under various accelerative and head loading conditions were applied to understand the sensitivity of the Nij construct to changes in acceleration and helmet mass, as well as its stability with respect to gender, body mass, neck circumference, and sitting height. A portion of this data was combined with data from an earlier postmortem human subject study to create pilot study modified risk curves. These curves were compared and contrasted with the NHTSA risk curves. RESULTS: A statistically significant difference in the peak mean Nij was observed when seat acceleration increased by 2 G, but not when helmet mass was varied from 1.6 kg to 2 kg at a constant seat acceleration of 8 G. Although NHTSA risk curves predict a 13% risk of AIS 2+ injury for the 8-G, 2-kg helmet condition mean Nij of 0.138, no AIS 2+ injuries were observed. Modified risk curves were produced which predict a 0.91% risk of AIS 2+ injury under these conditions. DISCUSSION: The Nij was shown to be sensitive to changes in acceleration and generally robust to anthropometric differences between individuals. Modified risk curves are proposed which improve risk prediction at lower Nij values.

Musculoskeletal Injuries and Automation in Aerial Port Operations.

INTRODUCTION: Aerial ports are being modernized with automated technologies, but the impact on musculoskeletal injury (MSKI) is unknown.METHODS: In this retrospective cohort study of U.S. Air Force aerial port technicians and traffic management technicians, we compared reported injury rates from January 2006-December 2016 and Veterans Benefits Administration disability compensation claims awarded from January 2001-March 2017. Ton-adjusted injury rates, associated lost/affected duty time, and percent risk attributable to lack of automation were compared at Dover Air Force Base (which features base-specific automation), Travis Air Force Base, Ramstein Air Base, and Yokota Air Base.RESULTS: Injuries most often occurred during aircraft/flight line activities and were typically sprains/strains, with extremities being most affected. Among aerial port technicians there were 8.0 injury reports per 1000 person-years compared to 5.2 per 1000 among traffic management technicians (incidence rate ratio = 1.5; 95% CI: 0.9, 3.0). Of the aerial port technicians with a compensation award, 70.7% included an MSKI component, whereas 75.7% of traffic management awards included an MSKI component. Aerial port technicians at Dover AFB experienced 1.4 injury reports per 1000 personnel per 1000 cargo-tons per year, lower than the other ports: 3.2 (Travis); 3.7 (Ramstein); and 7.6 (Yokota). Overall, 56% of injuries at Travis, 62% at Ramstein, and 82% at Yokota could be attributed to absence of Dover-like automation. However, mean lost/affected duty days at Dover (12.4) far exceeded those at the other bases (range: 4.5-8.6).DISCUSSION: Automating aerial ports may reduce injury rates, but the impact on lost/affected duty time requires further investigation.Bylsma VFH, Webber BJ, Erich RA, Voss JD. Musculoskeletal injuries and automation in aerial port operations. Aerosp Med Hum Perform. 2020; 91(8):669-673.

Public Health Response to Zika Virus Exposure of Air Force Members Deployed to Caribbean Islands, 2016.

INTRODUCTION: The emergence of Zika virus disease (ZVD) in areas of military operations provided a new opportunity for force health protection. ZVD infection had an estimated 4:1 asymptomatic-to-symptomatic ratio and can cause neurologic sequelae. MATERIALS AND METHODS: We provide a brief report of a field investigation utilizing laboratory-based surveillance and survey instruments to characterize ZVD risk among personnel deployed to the Dominican Republic in support of Operation NEW HORIZONS (NH). Additionally, we describe a cluster of 3 ZVD cases among 8 aircrew on a short mission to St. Croix (U.S. Virgin Islands). RESULTS: Following Operation NH, 6 of a total 189 deployed cohort members tested positive for ZVD by immunoglobulin M and confirmatory plaque reduction neutralization test (3.2%). Reverse transcription polymerase chain reaction testing in urine or serum was positive in 4 of those 6 cases. All 6 cases reported at least one symptom, with 5 reporting subjective fever and arthralgia and 4 reporting rash. Cases were less likely to have air-conditioned living quarters (odds ratio = 0.1; 95% confidence interval 0.02-0.77; P < 0.03), but were otherwise similar to non-cases. Likewise, in St. Croix, 3/8 tested positive by immunoglobulin M and plaque reduction neutralization test for an attack rate of 38%. Similar to Operation NH, all three cases were symptomatic with subjective fever (67%), arthralgia (67%), and/or rash (100%). CONCLUSIONS: This field investigation identified differing, mission location-dependent ZVD attack rates and a 0:9 asymptomatic-to-symptomatic case ratio. As this was unexpected based on a previous report of a 4:1 ratio, it emphasizes the need to be cautious before generalizing outbreak characteristics between populations while also offering additional practical experience for force health protection.

Malignancy in U.S. Air Force fighter pilots and other officers, 1986-2017: A retrospective cohort study.

OBJECTIVE: This study sought to determine the incidence rates of cancer, overall and by site, among active component U.S. Air Force fighter pilots, and to compare the rates with those in other active component Air Force officers. METHODS: Using a matched retrospective cohort design, U.S. Air Force fighter pilots were compared with other commissioned officers who entered active component service between 1 January 1986 and 31 December 2006. The cohort was followed for cancer diagnoses in TRICARE and the Veterans Health Administration from 1 October 1995 through 31 December 2017. Fighter pilots and non-fighter pilot officers were compared after matching on sex, age at first observation (15 age groups), and age at last observation (15 age groups). Sex-stratified overall and site-specific cancer rates were compared with matched Poisson regression to determine incidence rate ratios with 95% confidence intervals. RESULTS: During 1,412,590 person-years of follow-up, among the study population of 88,432 service members (4,949 fighter pilots and 83,483 matched officers), 977 incident cancer cases were diagnosed (86 in fighter pilots and 891 in matched officers). Male fighter pilots and matched officers had similar rates of all malignant cancers (RR = 1.04; 95% CI: 0.83-1.31) and of each cancer site. Female fighter pilots and matched officers also had similar rates of all malignant cancers (RR = 0.99; 95% CI: 0.25-4.04). DISCUSSION: In the active component U.S. Air Force, fighter pilots and their officer peers had similar overall and site-specific cancer rates.

Postoperative Hyperglycemia Can Be Safely and Effectively Controlled in Both Diabetic and Nondiabetic Patients with Use of a Subcutaneous Insulin Protocol.

BACKGROUND: Postoperative hyperglycemia related to stress has been shown to be an independent risk factor for periprosthetic joint infection. In a non-intensive care, general-surgery setting, a standardized postoperative insulin protocol has been shown to decrease the rate of wound infections. We hypothesized that the use of a similar protocol is both safe and effective for controlling hyperglycemia in patients who have undergone total joint replacement. METHODS: We performed a retrospective cohort study of 489 consecutive patients who underwent primary or revision total hip or knee arthroplasty between January 2008 and April 2013. All patients were tested with point-of-care (finger-stick) glucose determinations postoperatively and were started on a subcutaneous insulin protocol if they had postoperative stress hyperglycemia of >140 mg/dL when fasting or >180 mg/dL after meals. Insulin was discontinued when blood glucose decreased to <100 mg/dL. RESULTS: Of the 489 patients, 301 (62%) qualified for the insulin protocol. Thirty-seven (17%) of the 220 patients for whom the hemoglobin A1c level was available were diabetic, and 21 (11%) of the 187 patients for whom body mass index data were available were morbidly obese (body mass index, ≥40 kg/m2). Diabetes (p < 0.001), revision surgery (p < 0.001), male sex (p = 0.0110), and obesity (including morbid obesity) (p = 0.0051) were independent factors resulting in significant glycemic elevation. A trend toward hyperglycemia occurred in younger patients but did not reach significance (p = 0.063). The glucose levels of patients in all of these groups responded well to insulin. None of the patients who were managed with the insulin experienced a periprosthetic joint infection. There were no injuries related to hypoglycemia. CONCLUSIONS: The findings of the present study suggest that hyperglycemia is a common link between seemingly disparate factors related to the increased prevalence of periprosthetic joint infection. The standardized subcutaneous insulin protocol was both safe and effective for the treatment of hyperglycemia for nondiabetic as well as diabetic patients. Patients who have undergone total joint replacement, especially those with revision procedures, male sex, morbid obesity, and diabetes, should be evaluated for hyperglycemia starting in the post-anesthesia care unit and should be managed with the insulin protocol when that risk is identified. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

The Impact of Environment and Occupation on the Health and Safety of Active Duty Air Force Members: Database Development and De-Identification.

Preparing data for medical research can be challenging, detail oriented, and time consuming. Transcription errors, missing or nonsensical data, and records not applicable to the study population may hamper progress and, if unaddressed, can lead to erroneous conclusions. In addition, study data may be housed in multiple disparate databases and complex formats. Merging methods may be incomplete to obtain temporally synchronized data elements. We created a comprehensive database to explore the general hypothesis that environmental and occupational factors influence health outcomes and risk-taking behavior among active duty Air Force personnel. Several databases containing demographics, medical records, health survey responses, and safety incident reports were cleaned, validated, and linked to form a comprehensive, relational database. The final step involved removing and transforming personally identifiable information to form a Health Insurance Portability and Accountability Act compliant limited database. Initial data consisted of over 62.8 million records containing 221 variables. When completed, approximately 23.9 million clean and valid records with 214 variables remained. With a clean, robust database, future analysis aims to identify high-risk career fields for targeted interventions or uncover potential protective factors in low-risk career fields.