Prevalence and risk factors of low back pain in military personnel: a systematic review

Abstract

Purpose

• Low back pain (LBP) has a significant impact on the general population, especially on military personnel. This study aimed to systematically review the relevant literature to determine the prevalence and risk factors of low back pain among military personnel from different military occupational categories.

Methods

• For this systematic review, we searched Embase, PubMed, and Cochrane. We performed study selection, data extraction, and assessed the quality of the evidence using the adapted risk of bias assessment tool by Hoy et al. This review process was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. This study is registered on the Center for Open Science, registration DOI: 10.17605/OSF.IO/HRGE8.

Results

• Out of 860 papers, 19 studies met the inclusion criteria. More than 360 000 military people with lumbar pain situation were considered for inclusion in this systematic review. The 1-year prevalence of LBP could be up to 81.7% in the Army, 5.2% in the Marines, and 48.1% in the Air Force. Age (OR = 0.494–2.89), history of LBP (OR = 2.2–8.91), and sedentary position (OR = 0.55–3.63) were the most common physical, sociodemographic, and occupational risk factors, respectively.

Conclusions

• Low back pain was prevalent among military personnel. There was heterogeneity in studies and a significant difference in prevalence and incidence across various occupational categories. Physical, sociodemographic, and occupational risk factors were researched more than psychological risk factors in the military.

Introduction

Low back pain (LBP) is a frequently experienced medical condition and a main contributor to the overall burden of musculoskeletal conditions, with 570 million prevalent cases worldwide (1, 2). LBP is usually defined as pain, muscle tension, or stiffness localized below the costal margin and above the inferior gluteal folds, with or without leg pain (sciatica) (3). The diagnostic process is mainly focused on the triage of patients with specific or non-specific LBP. Specific LBP is defined as symptoms caused by a particular pathophysiological mechanism, including vertebral fractures, inflammatory disorders, malignancy, infections, osteoporosis, rheumatoid arthritis, and intra-abdominal causes (3, 4). However, a specific nociceptive cause of LBP is rarely identified; thus, LBP is typically classified as non-specific with an indeterminate pathoanatomical cause of the pain, a common form of LBP that occurs in 85% of cases (commonly cited as 90% in articles) (5, 6, 7). LBP has been the single leading cause of disability, reduced quality reduction of life, and ability impairments worldwide, thereby constituting a serious socioeconomic burden on patients and society (2, 4, 8). In the United States, LBP was ranked fifth among diseases and injuries that contribute to disability-adjusted life years and first for medical expenditures among 154 health conditions of LBP (9, 10).

A study in the United States revealed that the maximum lifetime prevalence of LBP in the general population is 84% in adults, with an average prevalence of 39% (1, 11, 12). The mean point prevalence of LBP in a previous review was estimated at 18.3%, with a 1-month prevalence of 30.8% (5). The prevalence of athletes who have experienced intense physical activities demonstrated higher values than in the general population, with a lifetime prevalence range of 1–94% and 18–65% for the point prevalence (13). Modern military personnel are exposed to many intense physically demanding tasks associated with multiple musculoskeletal symptoms and injuries that lead to LBP (14, 15). Annual prevalence percentage values of LBP in the military were high at 9–89.38% for (16, 17). However, a previous study described variable prevalence rates and calculated it at roughly 40.5 per 1000 person-years for the incidence rate in the armed forces (18). The comparison of military personnel and the general population in the same age group demonstrated that the peak prevalence of the population occurs in the age group of over 40 years, with values at 40.5 per 1000 person-years and 536 per 10 000 person-years (18, 19). LBP in military personnel also exerts a serious socioeconomic effect. Annual data in the British Army presented that lumbar pain leads to the maximum loss of 11% of military personnel working days (20). Chronic LBP is a dominant reason for medical expenses among active-duty and ex-soldier personnel (21), with an annual economic burden of around £2.8 billion in the UK (22), more than $4.8 billion in Australia (23), and over $100 billion in the US (24). The nature of LBP could also result in nonquantifiable costs, such as struggles with relationships, depression, and anxiety, in military personnel (25).

Previous studies reported various risk factors of LBP in the general population (26, 27). Many cases of LBP have been associated with genomes linked to overweightness/obesity and dyslipidemia (28, 29). Military personnel categories present different occupational demands, such as exposure to noise, twisted body positions during work, and training courses, which are potential risk factors for LBP (30, 31, 32).

Understanding variables that may contribute to the development of LBP and the burden of LBP is necessary given the high prevalence and various risk factors of LBP in the military population. Clearly identifying the prevalence and risk factors of LBP can minimize the effect of LBP on active-duty military personnel. However, previous studies on the prevalence, incidence, or risk factors for LBP using different military populations and various methods reported distinct results. Meanwhile, a few reviews have summarized prevalence and risk factors for LBP on the basis of different military occupations.

This systematic review aimed to describe the prevalence of LBP among different categories of military personnel on active duty and review the risk factors for lumbar pain based on the basis of different categorized populations in relation to military personnel.

Materials and methods

Search strategy

A systematic search was performed in PubMed, Embase, and the Cochrane Library to find pertinent studies. Studies published from their inception up to 28 February 2023 were searched for selection. The following search terms and their synonyms were used: LBP, military, air force, navy, army, soldier, and sailor. The key terms used to conduct the search were in Supplementary file 1 (see section on Supplementary Materials at the end of the article). EndNote X9 was utilized to download and handle the recognized articles. This review process was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines (33). This review was registered with registration doi: 10.17605/OSF.IO/HRGE8.

Eligibility criteria

The following were the criteria for inclusion: i) The cross-sectional, retrospective, and prospective cohort studies published in a peer-reviewed journal and written in English were included. ii) The study population was 18 years old or older at the start of the study regardless of gender, including in-service or retired military personnel of any military occupation. iii) The classifications of low back pain, such as specific and nonspecific LBP, were all considered. iv) Physical, psychosocial, sociodemographic, and occupational risk factors were all included in this systematic research. v) The studies about the prevalence and incidence of LBP in the military were considered.

The exclusion criteria were as follows: i) The study had no access to full-text articles. ii) The study had a sample of fewer than 50 people with lumbar pain, and a follow-up period of at least 3 months was omitted. iii) The study had an undefined prevalence period of LBP as a result of fracture/dislocation, tumor, inflammatory diseases, systemic diseases, infection, structural deformity, or other serious low back pathology were excluded (34, 35). iv) The study failed to report 95% CI and odds ratios (OR), risk ratios, hazard ratios (HR), and incidence rates (IR), and incidence rate ratios (IRR) of risk factors.

Selection of studies

Available studies were selected through a double-stage screening by two independent reviewers, XWY and ZYH. ZYH screened all records, and XWY screened the retrieved records. The two reviewers were unaware of each other’s choices of other persons involved in the first step, which involved screening titles and abstracts. Studies that were deemed insignificant or did not fulfill the inclusion criteria were removed, and the full-text literature of the remaining research was retrieved. Studies that were pertinent to the topic but not entirely relevant to the present review made it to the second stage for further assessment. The final selection was determined in the second step by the same reviewers, who screened the full-text studies against the eligibility criteria. Any disagreements were resolved through consensus sessions with the help of a third reviewer, YQH.

Study quality assessment

The risk of bias instrument, which was initially developed by Hoy et al. (36) for measuring prevalence studies and adapted to assess the quality of cohort and cross-sectional studies (Supplementary file 2), used four matters were used to evaluate external validity and six terms were used for evaluating internal validity. Studies that concluded with low and moderate risk of bias were analyzed in this review. In addition, studies with a high risk of bias were excluded to reduce the impact on confidence in the estimate.

Data extraction

A comprehensive data extraction form was designed by XWY and pretested using a few eligible studies. Amendments were made as suggested by all authors. Data were extracted by one reviewer, XWY, from all finally selected studies.

The following data were extracted: articles, author, time, country, study design, geography, the definition of LBP, population characteristics, the prevalence and incidence of LBP, follow-up period, prevalence time, risk factors for LBP, and method. The indexes associated with risk factors and prevalence, such as percentage (%), 95% CI, OR, relative risks (RR), HR, IR, and IRR, were extracted. Only adjusted data were extracted from included studies when they provided both adjusted and unadjusted values.

Data synthesis and analysis

The prevalence and cumulative incidence were extracted from studies by percent (%). As for the description of incidence rate, the number of LBP cases per 1000 person-months was extracted from studies or calculated by the definition of an incidence rate (the number of LBP cases by the sum of exposure times). Every risk factor for LBP related to physical, psychological, and occupational aspects from cohort and cross-sectional studies was considered and concluded. The studies were grouped by type of military occupation (Army, Marine, and Air Force). Comparison data were lacking due to methodological heterogeneity in the trials. Hence, no meta-analyses could be done. The information was presented descriptively.

Results

Identification and selection of studies

The selection processes of literature were demonstrated in Fig. 1. A total of 1339 articles were identified through searches for reasonable studies. After removing duplicate manuscripts, 860 studies remained. A total of 755 studies were removed after screening the titles and abstract because they did not meet the inclusion criteria. Full-text screening for the remaining 105 studies was performed. Eighty-six showed no accordance with the eligibility criteria. The 26 eligible studies (14, 15, 16, 28, 37, 38, 39, 40, 41) were critically appraised, and 19 studies (14, 15, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58) were deemed to be accessible quality studies with a low or moderate risk of bias.

Figure 1.

PRISMA flow chart of literature search and study selection.

Risk of bias of included studies

The results of the risk of bias assessment were presented (Table 1). All three authors participated in the risk of bias quality assessment of the terminal studies. In the overall estimation, 13 studies were concluded to have a low risk of bias (14, 15, 42, 44, 45, 46, 47, 49, 50, 52, 53, 54, 58), six literature had a medium risk of bias (43, 48, 51, 55, 56, 57), and six theses had a high risk of bias (28, 37, 38, 41, 40, 41). Most of the studies showing a high-level risk of bias did not show significant differences in relevant demographic characteristics between responders and non-responders. They lacked an accurate definition of lumbar pain, which was a major reason for their elimination. The unreasonable length of the prevalence period (less than 3 months) and inappropriate numerator and denominator parameters of interest were common reasons for excluding studies. In general, the external validity of the literature was better than the internal validity after excluding the theses that had a high risk of bias.

Table 1.

Risk of bias assessment of the 26 included articles grouped by the study population.

Study	External validity*				Internal validity†						Summary of overall RoBa
	1	2	3	4	5	6	7	8	9	10
Gun et al. (53)	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Low
Sidiq et al. (54)	Y	Y	Y	N	Y	Y	Y	Y	Y	Y	Low
Arellano et al. (28)	Y	Y	Y	N	Y	N	N	Y	N	N	High
Alizadeh et al. (16)	Y	Y	Y	N	Y	N	Y	Y	N	N	High
Monnier et al. (47)	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Low
Posch et al. (52)	Y	Y	Y	N	Y	Y	Y	Y	Y	Y	Low
Zack et al. (55)	N	N	Y	Y	Y	Y	Y	Y	Y	Y	Moderate
Wei et al. (58)	Y	Y	Y	N	Y	Y	Y	Y	Y	Y	Low
Seay et al. (49)	N	Y	Y	Y	Y	Y	Y	Y	Y	Y	Low
Moshe et al. (45)	Y	Y	Y	Y	Y	N	Y	Y	Y	Y	Low
Çınar et al. (41)	Y	Y	Y	N	Y	N	Y	Y	N	N	High
Nissen et al. (43)	N	N	Y	N	Y	Y	Y	Y	Y	Y	Moderate
Knox et al. (51)	N	N	Y	Y	Y	Y	Y	Y	Y	Y	Moderate
Roy et al. (42)	Y	Y	Y	N	Y	Y	Y	Y	Y	Y	Low
Roy et al. (46)	Y	Y	Y	N	Y	Y	Y	Y	Y	Y	Low
Taanila et al. (15)	Y	Y	Y	N	Y	Y	Y	Y	Y	Y	Low
MacGregor et al. (50)	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Low
Ernat et al. (14)	Y	Y	Y	Y	Y	Y	Y	Y	Y	Y	Low
Grossman et al. (37)	Y	Y	Y	N	Y	N	N	Y	N	N	High
Secer et al. (39)	Y	Y	Y	N	Y	N	N	Y	Y	N	High
Nevin & Means (40)	Y	N	Y	N	Y	N	N	Y	Y	Y	High
Rozali et al. (48)	N	N	Y	Y	Y	Y	Y	Y	Y	Y	Moderate
Mattila et al. (56)	Y	Y	Y	Y	Y	N	Y	Y	N	Y	Moderate
Strowbridge (44)	Y	Y	Y	N	Y	Y	Y	Y	Y	Y	Low
Hestbaek et al. (57)	Y	Y	Y	N	N	Y	Y	Y	Y	Y	Moderate
Strowbridge (44)	N	N	Y	N	Y	N	N	Y	Y	N	High

^aSummary of overall risk of bias indicated by color (Low = low risk of bias, further research is very unlikely to change confidence in the estimate; Moderate = moderate risk of bias, further research is likely to have an important impact on confidence in the estimate and may change the estimate; High = high risk of bias, further research is very likely to have an important impact on confidence in the estimate and is likely to change the estimate).

*External validity: 1, Target population representative; 2, Sampling frame representative of the target; 3, Random selection or census undertaken; 4, Non-response bias minimal.

^†Internal validity: 5, Data collected directly from the subjects; 6, An acceptable definition of low back pain; 7, Instrument that measured the parameters of interest valid; 8, Same mode of data collection used for all subjects; 9, Length of the shortest prevalence period for the parameter of interest appropriate.; 10, Numerator(s) and denominator(s) for the parameter of interest appropriate. Y, Yes (low risk of bias); N, No (high risk of bias).

Characteristics of included studies

The synopsis of characteristics of included studies was illustrated in eTable 1 (Supplementary file 3). Sixteen studies assessed the prevalence and risk factors of the Army personnel (i.e. driver and deployment army) (14, 15, 43, 454, 46, 48, 49, 54, 55, 56, 58), two studies assessed those of the Marines (47, 50), and one study assessed those of the Air Force (52). Most of the qualified studies were from the United States (7/19) (14, 42, 46, 49, 50, 51, 53). Two studies were conducted in each of the following countries: Israel (45, 55), Finland (15, 56), and Denmark (43, 57). One study was conducted in each of the following countries: Sweden (47), Arabia (54), China (58), Malaysia (48), Britain (44), and Austria (52). Prevalence and risk factors for lumbar pain among military personnel that were grouped by occupation are presented chronologically in eTable 2 (supplementary file 4) and eTable 3 (supplementary file 5).

Prevalence/incidence analysis

LBP in the Army

Fourteen studies about the prevalence and incidence of LBP in the Army were included in this review.

First, from an age perspective, Gun et al. demonstrated that the 2-year prevalence of LBP in ages less than 20 was 20.05% and the age between 20 and 29 years was 30.05% (53). However, for the 18–22-year-old soldiers, a 1-year prevalence of 42% for LBP was reported by Hestbaek et al. (57).

Second, in terms of sex, Seay et al. reported that the incidence rate was 13.58 per 1000 person-months in females and 7.36 per 1000 person-months in males (49). Similarly, Knox et al. concluded that the incidence rate was 7.62 per 1000 person-months in females and 4.07 per 1000 person-months in males (58).

LBP in Marines

Two studies about the incidence or prevalence of LBP in the Marines were included in this review.

First, from an occupational point of view, MacGregor et al. deduced that the 1-year prevalence of LBP in the service or supply occupations was highest with 5.2%, whereas the prevalence in communications or intelligence occupations was lowest with 3.2% (50).

Second, from the national perspective, Monnier et al. presented that the incidence rate of LBP was 418.5 per 1000 person-months, and the incidence rate of LBP that limited workability was 195.3 per 1000 person-months among Swedish Marines (47). In the U.S. Marines, MacGregor et al. concluded that the 1-year prevalence of LBP was 4.1% (50).

LBP in the Air Force

One study, which was conducted by Posch et al., showed that the prevalence of LBP within 12 months was 48.1% among helicopter pilots and 36.8% among crewmembers (52).

Risk factor identification

Risk factor identification was classified into four categories, namely, physical, psychological, sociodemographic, and occupational. Both significant risk factors and non-significant findings were summarized in eTable 2.

Risk factors for LBP in the Army

Physical risk factors

For physical risk factors with statistical significance, a history of LBP (OR = 2.20–8.91) had a consistent association with lumbar pain among active armed military personnel (42, 46, 58), and LBP family history (OR = 1.615) was also demonstrated as a connection between LBP and the active Army (58). Similarly, previous diseases other than back-related ones (OR = 2.0) (56) and previous injuries such as lower extremity injuries (HR = 1.43–1.76) (49) or sports injuries (HR = 1.70) (15) were consistently associated with LBP. One research study illustrated that the connection between participation in additional strength training (OR = 0.88) and LBP led to a risk of suffering (42). One study demonstrated that nightmare frequency in military service and bad sleep quality were associated with a higher risk (OR = 2.391–3.386) of lumbar pain (58).

Psychological risk factors

Nissen et al. concluded that support from leaders and psychological stress were statistically significant predictors (OR = 1.69–1.71) of LBP. At the same time, Strowbridge et al. concluded that off-duty pursuit (OR = 2.91) is associated with LBP.

Sociodemographic risk factors

As a statistically significant sociodemographic risk factor, being female (OR = 1.66, IRR = 1.45) was consistently associated with LBP. Gun et al. deduced that female members were more likely to experience LBP than males (53). Knox et al. put forward that gender as female had a strong association with LBP (51). Additionally, lower education levels (HR = 1.5–1.6) showed a relation to LBP (15). Moreover, an association was found between marital status and LBP. When compared with single personnel, married individuals (IRR = 0.87) were less likely to suffer from LBP (51). Additionally, Hestbaek et al. concluded that being a parent with higher education (OR = 1.9) was a statistically significant factor (57).

Occupational risk factors

Several statistically significant occupational risk factors were found for prevalent LBP (44). Moshe et al. (45) and Zack et al. (55) concluded that occupational categories (RR = 0.49–2.6), including administrative units, maintenance units, combat units, car drivers, and truck drivers, had different degrees of association with LBP. Regarding service type, Taanila et al. (15) concluded that engineers (compared with anti-tank personnel) (HR = 2.0) were associated with a higher LBP risk. In addition, body armor (OR = 1.14–1.30) as a constant risk factor illustrated the association with LBP, with one study demonstrating that participants who wore body armor were more likely to experience LBP than those who did not (42), and the time spent wearing body armor (OR = 1.13–1.16) was also associated with LBP (46). Nissen et al. (43) concluded that an awkward working position was a statistically significant factor. Rozali et al. (48) concluded that driving in a forward bending and sitting position was a statistically significant factor (OR = 1.98–3.63). Additionally, Hestbaek et al. (57) deemed that sedentary and light military drills (OR = 0.55–1.578) were related to danger factors for lumbar pain. Furthermore, job duties, equipment weight, whole-body vibration, and working environment were statistically significant factors (OR = 1.01–2.60) (42, 43, 46, 48).

Risk factors for LBP in Marines

Physical risk factors

As a statistically significant factor, people with a history of LBP (HR = 2.47–3.58) over the past 6 months were at risk of both LBP and LBP that limits workability, as shown by Monnier et al. The time spent on physical training (HR = 2.9) was also linked with LBP occurrence. One study reported that participants with less physical training weekly were at a greater risk of losing workability due to LBP than people who had more training. Poor performance in physical fitness tests (HR = 1.87) was also associated with LBP. Additionally, a report demonstrated the relationship between height (HR = 1.98-4.48) and LBP. One study presented that shorter height had a greater association with LBP occurrence and workability limitation (47).

Sociodemographic risk factors

In terms of gender, MacGregor et al. presented that males were less likely to suffer from LBP than females (OR = 1.94), and this study also reckoned that it was hard to observe a relationship between age and LBP (50).

Occupational risk factors

One study reported that mid-level ranks (OR = 0.73) (vs junior ranks) were a risk factor for LBP in a statistical sense. In addition, occupational categories (OR = 1.31–1.33), such as service/supply and electrical/mechanical/craftworker, were more likely to experience LBP than those who were administrative or other (50).

In the study of active military in the United States, a tangible association between deployment location and time and LBP was not found (50).

Risk factors for LBP in the Air Force

Independent relevant risk factors, whether in physical, psychological, sociodemographic, or occupational field, that demonstrated a relationship with LBP suffering were not found.

Discussion

The objective of this systematic review was to synthesize the observational literature on the prevalence and risk factors of LBP in the military population. Nineteen pertinent cohort studies were identified. More than 360 000 people with LBP in the past two decades were included in this systematic review. The findings of this study underscored the high prevalence and incidence of LBP in the military and demonstrated 59 risk factors for LBP. Low back pain is a long-standing and common general health problem associated with multiple factors in military personnel worldwide.

The 1-year prevalence results in this review vary significantly from 7% to 81.7% (48, 52, 53, 54, 56, 57, 58). Meanwhile, other studies on Israeli military recruits have reported a lower prevalence of lumbar pain of 0.29% (59) but a higher rate of 74.2% among military police was indicated in Brazil (60). The analysis of the incidence of other studies also demonstrated an evident range gap of 1.13–22.33 per 1000 person-months and 0.046% to 83.9% (14, 15, 42, 44, 45, 46, 47, 49, 50, 51, 55, 61) because of definitions of LBP, epidemiological investigation methods (cross-sectional or cohort studies), length of follow-up periods, characteristics of the population studied (sample size, response rate, and representativeness), methods of data collection (questionnaires, physical examinations, or medical database), and recall bias (43, 47, 58). Studies with low prevalence rely on medical records (45, 50) and use additional stringent eligibility criteria. This scenario is likely due to the decreased willingness of this population to seek medical care treatment because they assume that LBP is a normal part of their occupation and such medical encounters may be detrimental to their careers, thereby ignoring or minimizing the severity of this condition (14, 45, 54, 62). Furthermore, persons with severe back and other chronic disorders or a history of prior injury are typically excluded from the sample under the assumption that these people are incapable of performing physically demanding military tasks (49, 56).

Moreover, military occupational categories, such as infantry personnel (low prevalence of LBP) and army service members, demonstrated different values of LBP prevalence, with a threefold increase in risk compared with marines (51). A previous study reported that infantry soldiers did not have a higher rate of LBP than soldiers in other battalions, likely because of superior premorbid levels of physical fitness (42). However, the prevalence of mild LBP was always higher than that of severe pain for military personnel regardless of the occupation. These findings may result of a different levels of physical fitness and training regimens, given that a high level and high pain tolerance could protect against LBP (14, 54, 58, 59, 62, 63). Similarly, studies that interpret physical training as a protective factor against LBP reveal that the prevalence and incidence of LBP among runners are lower than the general population (64).

However, not all differences in results of incidences/prevalences can be explained and applied to the target population. First, the prevalence reported by Sidiq et al. (54) is potentially biased because the number of respondents is not reported in the article. Second, the number of LBP cases was inaccurate in research by Roy et al. (42) and the exposure time was unreported in most studies (except Monnier et al. (47), Ernat et al. (14)), which mean there may be certain deviations in the calculated results. Third, many studies report widely varying data within one population group, such as the articles by Moshe et al. (45) and Strowbridge et al. (44), deserve more attention to suspect and explore their accuracy. Fourth, the prevalence in the small sample sizes reported by Posch et al. (52), Monnier et al. (47), and Rozali et al. (48) require further confirmation through a larger sample.

Risk factors of the general population or military personnel, such as age, obesity, sex, tobacco use, educational level, history of LBP, and lifestyle, have been thoroughly discussed in previous reviews (65, 66, 67). However, many specific risks existing in the military population require further investigation (68). Junior rank personnel often undergo more rigorous physical work that results in LBP, with more opportunities for back injuries, compared with senior officers who generally perform less physically demanding work based on their duty description and nature of work (53). Hence, enlisted soldiers typically suffer more from LBP than other levels in the military population (34, 53).

Some risk factors are specific to the military occupation. Risk factors specific to the Air Force include g-force exposure in pilots and airmen, extreme shock and vibration exposure, mission injury, and falls incurred during airborne activities (69, 70). Frequent exposure to high positive G-force values causes premature disc degeneration in the lumbar spine (69). Whole-body vibration can increase not only the latency and the magnitude of response of the erector spinae but also the fatigue of back musculature (51). Combat deployment-related variables, such as carrying combat load requirements, performing dismounted patrols, and lifting heavy supplies, were highly associated with LBP in the Army and Marine (43, 46, 47). Body armor and heavy loads lead to lower back pain (LBP) due to several biomechanical reasons (71). Intervertebral discs may undergo degenerative changes due to loading. Carrying heavy backpacks may cause the person to lean forward, leading to inadequate stress distribution in the spine and compression of the front of the disc. This scenario may increase the risk of shear-lean injuries in the lower back. Muscles in the trunk can help stabilize the spine, but muscle activation also increases as the load increases. However, soldiers may be unable to sustain the necessary muscle contractions at high weight values or once fatigue sets in (46).

Psychosocial factors have been increasingly recognized as important and common risk factors in the development of LBP (62, 70, 72). The military population may encounter psychosocial barriers, including pressure to meet specific professional and physical requirements as well as the thought of succumbing to injuries, which may discourage them from seeking medical attention (14, 45). Sleep disturbances, work dissatisfaction, low self-efficacy, and low coping ability are increased risk factors that adversely affect outcomes in patients with LBP (42, 58, 73). Catastrophizing and kinesiophobia lead to deconditioning and the perpetuation of pain (62). The risk of concomitant psychological trauma, such as post-traumatic stress disorder (PTSD), major depressive episodes, generalized anxiety disorder, and panic disorder, are also considerable factors for military personnel with LBP (14, 70). PTSD and chronic LBP may mutually reinforce each other and increase the likelihood of soldiers discontinuing their military service (21).

The practice of lumbar pain management is manifold. The findings of the present study could help strengthen secondary preventive measures for LBP in the military (47, 74, 75). First, maintaining satisfactory physical fitness and conditioning can help reduce the risk of LBP in military personnel (47, 76). Improved control of the lumbar neutral zone with trunk muscles through adequate isometric back endurance and exercises that improve flexibility and balance can play a protective role in LBP in the military (15, 77). Second, education and training programs can be provided to military personnel to teach them how to lift, carry, and move heavy equipment and materials correctly, as well as maintain proper posture and body mechanics during physical activity (15, 78). Finally, early intervention and treatment of LBP can also help prevent the recurrence or chronicity of the condition (75) through early assessment, diagnosis, and treatment by healthcare providers and rehabilitative services (79). Stepped-care intervention, telecare collaborative management, and multimodal approaches can increase the proportion of primary care patients with improved LBP (80, 81, 82). These preventive management strategies encourage the implementation of comprehensive measures to improve the health and readiness of soldiers.

This systematic review presents the following limitations. First, other potentially suitable studies might have been overlooked because this review only considered publications in peer-reviewed academic journals in the English language. Second, the optimal definition of LBP in prevalent studies remains unsatisfactory because of its diverse definitions among the included articles. Finally, the ratio of risk factors is included without partition or unification; these were inconvenient to compare.

Implications

The identified risk factors and prevalence in this review could emphasize the importance of LBP and provide ideas for preventing LBP in the military population by regulating risk factors in life and work. A detailed collection of exposure information is essential for future military studies on LBP to determine different contributing factors and refine occupation-specific LBP prevention efforts (50). Moreover, rehabilitation programs could optimize patient management by taking these factors into account (62).

Further research

On the basis of the results of the present review, future studies can improve research on the Marine and Air Force to broaden and deepen the comprehension of LBP prevalence and risk factors among military personnel further. Moreover, further research is needed to control sample homogeneity and specific work-related exposure, and a standardized case definition of LBP is necessary to facilitate the comparison of prevalence rates among various groups. Note that identifying additional focused areas of intervention and potential mitigation is necessary to customize preventive health programs to specific occupations.

Conclusion

By systematically concluding the prevalence of LBP in military occupational settings, there was heterogeneity in studies and different prevalent ranges in various occupational categories, i.e. change in the Army were more obvious than those in the Marine. There were numerous recognized risk factors for LBP from physical, psychological, sociodemographic, and occupational perspectives, but few conclusions have been made on psychological factors. The summary of risk factors in the Army was the most comprehensive, with multi-angle discussion, whereas the conclusions in the Air Force were relatively deficient.

ICMJE Conflict of Interest Statement

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the study reported.

Funding Statement

This work was supported by the National Natural Science Foundation of China (grant no. 82372578).

Availability of data and materials

The data and materials are all available from this review upon reasonable request to the corresponding author.

Author contribution statement

WYX and YHZ drafted the manuscript and searched the literature to identify eligible trials. WYX, YHZ, and XQW extracted and analyzed data. XQW and QHY conceived and revised this systematic review. XQW received the funding for this study. All the authors agreed with the conclusions of this systematic review, and all authors read and approved the final manuscript.