Recommended Content:
Medical Surveillance Monthly Report
What are the new findings?
The hospitalization rate among U.S. active component service members in 2023 at U.S. military and non-military medical facilities was 48.8 per 1,000 person-years, approximately 9% lower than the 2022 rate. As in prior years, over half (56.7%) of hospitalizations for active component members were associated with primary diagnoses in two categories: mental health disorders and pregnancy conditions. COVID-19 accounted for less than 0.1% of total active component hospitalizations in 2023, representing a greater than 85% decline from 0.4% in 2022, and a nearly 96% decline from 1.5% in 2021.
What is the impact on readiness and force health protection?
As in prior years, mental health disorders, including substance abuse disorders, were associated with the longest median hospital stay, six days; 5% of hospitalizations for mental health disorders had durations greater than 30 days. Prolonged hospitalizations, after care, and early attrition due to these common disorders can diminish not merely individual but unit operational readiness.
Background
This report documents the frequencies, rates, trends, and distributions of hospitalization among active component members of the U.S. Army, Navy, Air Force, Space Force, and Marine Corps during calendar year 2023. Summaries are based on standardized hospitalization records at U.S. military and non-military (reimbursed through the Military Health System) medical facilities worldwide that are routinely maintained in the Defense Medical Surveillance System.
In this report, primary (first-listed) discharge diagnoses are considered indicative of the primary cause of hospitalization. As in prior MSMR reports, summaries are based on the first 3 digits of the International Classification of Diseases, 10th Revision codes of the primary discharge diagnoses. Hospitalizations not routinely documented by standardized, automated records, e.g., during field training exercises or while shipboard, are not available in a centralized location for health surveillance purposes and are excluded from this report. Incidence rates were calculated per 1,000 person-years (p-yrs). Percent change in incidence was calculated using unrounded rates.
Frequencies, rates, and trends
In 2023, 62,806 hospitalizations were recorded for the active component members of the U.S. Army, Navy, Air Force, Space Force, and Marine Corps (Table 1); 45.3% of these hospitalizations were in non-military facilities (data not shown), compared to 46.4% in 2022.
Between 2014 and 2023, hospitalization rates manifested a general downward trend, but with annual fluctuations. Prior to 2020, the rates per 1,000 p-yrs fluctuated within a range, from a high of 55.7 in 2014 to a low of 52.7 in 2018, with an average annual percent change of less than 3% (-0.3% to +2.5%). In 2020, however, the hospitalization rate dropped sharply, below the typical range to 49.0, with a 9.4% decrease compared to 2019, the previous year. The rates in 2021 and 2022 then rebounded to their pre-pandemic range. As of April 2024, the crude annual hospitalization rate for 2023 was 48.8 per 1,000 p-yrs, approximately 9.0% lower than the rate in 2022 and comparable to the rate observed in 2020 (Figure 1).
Hospitalizations, by ICD-10 major diagnostic categories
In 2023, only four ICD-10 major diagnostic categories accounted for almost three-quarters (73.0%) of all active component hospitalizations: mental health disorders (31.1%), pregnancy- and delivery-related conditions (25.6%), injury and poisoning (8.7%), and digestive system disorders (7.6%) (Table 1). Consistent with the findings in 2019 and 2021, hospitalizations for mental health disorders in 2023 accounted for more than any other major diagnostic category; 2009 was the last year in which another diagnostic category, pregnancy- and delivery-related conditions, surpassed hospitalizations for mental health disorders (data not shown). COVID-19 accounted for less than 0.1% of total hospitalizations among active component service members in 2023, a decline greater than 85% from the previous year, when 0.4% of hospitalizations were due to COVID-19, and represents a decline of nearly 96% from the 2021 figure of 1.5%.
The latest data indicate that, from 2019 through 2023, both the numbers and rates of hospitalizations decreased for all major diagnostic categories (Table 1). The three largest declines, by number and percent rate of hospitalization, were observed for musculoskeletal system and connective tissue (1,273 fewer hospitalizations; 24.2% rate decrease) conditions, injury and poisoning (-1,229; -16.6%), and ‘other’ (-1,123; -48.4%). COVID-19 ranked next in terms of decline in hospitalization numbers, at 980, but demonstrated the highest percent decline (-91.9%) in the hospitalization rate. Additional categories with substantially decreased hospital admission rates included respiratory system (-797; -35.0%), signs, symptoms and ill-defined conditions (-860; -25.8%), and skin and subcutaneous tissue (-338; - 29.0%).
The relative proportion of hospitalizations by major diagnostic category was generally stable over the surveillance period (Table 1). COVID-19, which was included as a separate diagnostic category in 2020 and ranked thirteenth in total hospitalizations in 2021, dropped to the lowest ranking, eighteenth, in 2023.
Hospitalizations, by sex
In 2023, the hospitalization rate (for all causes) among service women was more than three times that of service men (116.5 per 1,000 p-yrs and 34.3 per 1,000 p-yrs, respectively). These data are consistent with national hospitalization rate trends published in 2022 for women and men ages 18-44 years (95 per 1,000 p-yrs and 37 per 1,000 p-yrs respectively) in the general U.S. population.1 Excluding pregnancy- and delivery-related conditions, the rate of hospitalizations among women (45.6 per 1,000 p-yrs) was 33.0% higher than among men (34.3 per 1,000 p-yrs) in 2023 (data not shown). This rate difference was primarily due to hospitalizations for mental health disorders (female:male rate difference [RD]: 6.1 per 1,000 p-yrs) and genitourinary disorders (RD: 2.6 per 1,000 p-yrs) (data not shown). Excluding pregnancy- and delivery-related conditions, hospitalization rates were relatively similar among men and women for the remaining 16 major diagnostic categories (data not shown).
Relationships between age and hospitalization rates varied by major diagnostic category (Figure 2). Rates among women in all age groups were consistently higher for the genitourinary, nervous and digestive system, hematologic and immune disorder, and infectious and parasitic disease categories. The gender gap was greatest for the genitourinary system category and widened with age, with the female-to-male ratio increasing from 4.0 in age categories under age 30 years to 6.6 in those older than 30. Similarly, hematologic and immune disorder rates were higher among women and with age increased from 1.5 to 3.1 times higher in women than men. Additionally, women had progressively higher (from 2.2 to 3.7 times) hospitalization rates within the neoplasms category, except for the youngest age group. In contrast, rates among men were higher than women in all age groups for the skin and subcutaneous tissue as well as respiratory and circulatory system categories. Hospitalization rates of mental health disorders were more than twice as high among younger women, under the 30 years of age, and were comparable among older age groups.
Hospitalization rates among both sexes generally increased with age for most diagnostic categories except mental health, injury and poisoning, skin and subcutaneous tissue, respiratory, and infectious and parasitic diseases. Rates decreased for both sexes with increasing age for mental health disorders and were relatively stable among all age groups for injury, infectious/parasitic diseases, respiratory system disorders, skin and subcutaneous tissue categories, as well as COVID-19.
Most frequent diagnoses
Mental health disorders represented a significant portion of hospital admissions among ACSMs. Adjustment disorders were the primary discharge diagnosis among both men (n=4,861) and women (n=1,321) (Tables 2 and 3) in 2023, accounting for nearly 10% of total hospitalizations. The next four most frequent diagnoses, for both sexes, were alcohol- and depression-related disorders, including recurrent major depressive disorder (severe without psychotic features), and posttraumatic stress disorder. Mental health disorder diagnoses, collectively, accounted for over 40% of all hospitalizations among men and, excluding pregnancy- and delivery-related conditions, among women.
Pregnancy- and delivery-related conditions constituted the top major diagnostic category for women, accounting for over three-fifths (60.8%) of all female hospitalizations, although adjustment disorders represented the most frequent cause of hospitalization when examining ICD-10 diagnoses through the fourth character code (Table 3).
Other common causes of hospitalization, regardless of sex, included ‘other and unspecified acute appendicitis’, ‘sepsis, unspecified organism’, and ‘other symptoms and signs involving emotional state’, as well as ‘other specified disorders of muscle’ for men, and ‘abnormal uterine and vagin*l bleeding’ for women.
Hospitalization durations
When graphically represented, hospitalization durations demonstrate a highly right-skewed (positive) distribution, with the lower limit equal to one day and a mode of three days. Because length of hospital stay is not normally distributed, the median duration with interquartile range was chosen as the best measure of central tendency. The median (IQR) duration of hospital stays (for all causes) has remained generally stable at three days, but increased to four (2-6) days in 2023 (Figure 3).
Medians and IQRs of hospitalization durations varied substantially by major diagnostic category. The shortest median durations of hospital stays, at 2 (2-6) days were observed for disorders of the musculoskeletal, genitourinary, and digestive systems, while the longest were for conditions in the ‘other’ and mental health diagnostic categories, where median (IQR) values were 5 (2-15) and 6 (4-11) days, respectively. Infectious and parasitic diseases had a median of 4 (2-6) days, and the remaining categories had a median of 3 (2-6 days).
Five percent of hospitalization stays exceeded 10 days for one half of ICD diagnostic categories: skin and subcutaneous tissue (11 days), circulatory system disorders (12 days), signs, symptoms and ill-defined conditions (19 days), nervous system/sense organ disorders (20 days), neoplasms (24 days), injury/poisoning (25 days), mental health disorders (34 days), and other non-pregnancy-related factors influencing health status and contact with health services (primarily orthopedic aftercare and rehabilitation following prior illness or injury) (41 days) (Figure 4).
Hospitalizations, by service
Among active component members of the Air Force and Space Force, pregnancy- and delivery-related conditions accounted for more hospitalizations than any other illnesses or injury category, while among active component members of the Army, Navy, and Marine Corps, mental health disorders were the leading cause of hospitalization (Table 4). This pattern has been observed in recent years. Prior to 2020, pregnancy- and delivery-related conditions were ranked first for both Navy and Air Force active component members. Among all the services, the crude hospitalization rate for mental health disorders was highest among active component Army members (17.7 per 1,000 p-yrs).
Injury was the third leading hospitalization category for all services, except the Air Force, where it was ranked fourth. The hospitalization rate for injury was highest among Army (5.3 per 1,000 p-yrs) and Marine Corps members (4.9 per 1,000 p-yrs), and lowest among Air Force and Space Force members (2.7 and 2.2 per 1,000 p-yrs, respectively); this service-ranked distribution has been observed since 2010.
Discussion
The crude annual hospitalization rate observed in 2023 marks the lowest recorded level from 2014 until 2023. Hospitalization rates demonstrated a general decreasing trend, with annual fluctuations, throughout the reporting period. In 2020 there was a significant decline, coincident with COVID-19-related changes in health care provision.
As in past years, in 2023 mental health disorders, pregnancy- and delivery-related conditions, and injury accounted for more than half of all active component hospitalizations. Adjustment disorders, alcohol dependence, depressive disorders, and PTSD were among the leading primary discharge diagnoses for both men and women. The continued decline of hospitalization frequencies and rates is attributed to a generalized decline among the major diagnostic categories since 2019, with substantial declines in the musculoskeletal system, injury, and ‘other’ categories.
Certain limitations should be considered when interpreting these results. This summary is based on primary (first-listed) discharge diagnoses only, but in many hospitalized cases multiple conditions can be present; for example, joint pain (category: musculoskeletal) may be co-listed with an injury (category: injury). In such cases, only the first-listed discharge diagnosis would be accounted in this report. This could underestimate hospitalization rates for common conditions by dividing them among two or more subcategories.
This is the second year DMSS data were housed and analyzed from the Military Health System Information Platform. Additionally, nearly all military treatment facilities are using GENESIS software to electronically capture medical care. Data completeness issues with data transfers between GENESIS to the Medical Data Store to DMSS have improved significantly since last year’s report. Regardless of whatever electronic system is used to capture hospitalization information, every hospitalization record requires completion of a discharge summary before the event record is reported in the system. Consequently, timeliness of reporting can still be an issue that may lead to underestimates of true counts and rates of hospitalizations for the most recent year of reporting. As a result, direct comparison between the 2023 data and data from prior years should be interpreted with caution.
Reference
- National Center for Health Statistics, U.S. Centers for Disease Control and Prevention. Table: people with hospital stays in the past year, by selected characteristics—United States, selected years 1997–2019. National Hospital Care Survey. Accessed May 13, 2024. https://www.cdc.gov/nchs/data/hus/2020-2021/HospStay.pdf
