Overview of Navy Medicine’s Limited Duty Patient Population
Authors: McWhorter Stephanie , Simon-Arndt Cynthia , Carlson Lori 
Published: November 2022

ABSTRACT

Introduction
U.S. Navy Medicine’s temporary limited duty (LIMDU) program is the primary vehicle for managing the medical care and subsequent career outcomes of the ill and injured active component (AC) Sailors and Marines to ensure a medically ready force. Before the LIMDU Sailor and Marine Readiness Tracker System (SMART) came online, it was very difficult to examine LIMDU program administration metrics, patients’ experiences during LIMDU, and their subsequent health and career outcomes. This study examined the LIMDU patient population’s demographic, military career, and LIMDU-specific characteristics; identified characteristics that differed significantly by military service; and evaluated potentially modifiable factors associated with patient outcomes.

Materials and Methods
A comprehensive SMART extract was used to identify all AC Sailors and Marines in active LIMDU status between October 1, 2016, and September 30, 2019. The SMART extract was merged with comprehensive administrative military personnel data by patient identifiers to create a longitudinal dataset and to conduct descriptive statistics, bivariate, and multivariate logistic regression analyses for this study. The sample included 26,591 AC Sailors and Marines with complete SMART and military personnel records who ended LIMDU on or before September 30, 2019.

Results
During the study’s 3-year period, Navy Medicine’s rate of initial LIMDU entry by AC personnel increased each year from 2,041 in FY2017 to 2,424 in FY2019 per 100,000 personnel. At the time of initial entry, most LIMDU patients were male (76%), E4–E6 paygrades (54%), and had a single diagnosis recorded in their SMART records (66%). Pain patients (23%) constituted the largest diagnostic group, followed closely by musculoskeletal patients (23%), and then mental and behavioral health patients (20%). Variables that might reflect administration practices of the program did not differ significantly by service, suggesting good internal standardization of LIMDU administration across Navy Medicine. However, bivariate and multivariate analyses identified significant differences by service for almost all personal demographic, LIMDU-specific, and post-LIMDU military career sample characteristics measured at the last LIMDU close date or later. Study results suggested that the Navy and Marine Corps referred Sailors and Marines to start LIMDU for different medical reasons; to receive care from different military treatment facilities; to close LIMDU with different final actions; and to experience different post-LIMDU career outcomes.

Conclusion
Navy Medicine’s SMART data is an important new resource for LIMDU program evaluation and population-level patient research, despite the data limitations and concerns identified and addressed by this study. The study results provide a baseline empirical understanding about the LIMDU patient population. Further research is necessary to interrogate the validity of these results over a longer period and to initiate other lines of inquiry. While the construction of the larger project’s LIMDU patient population longitudinal dataset required a significant initial investment, future dividends from ongoing work are anticipated. Results derived from verified SMART data will benefit Navy Medicine, operational commands, and LIMDU patients alike by informing continuing efforts to improve patient health and career outcomes, identify and implement best clinical and administrative practices, and optimize force readiness.