Self-evaluation of Health State in Chinese Navy of Different Fleets


 Objective: To clarify physical and psychological health state and potential medical need of Chinese navy. Methods: A cross-sectional study was performed in the total of 438 personnel of two fleets in different latitudes in China by self-reported questionnaire. The physical and psychological states were investigated and the potential medical needs were explored.Results: The top was muscle and skeletal system disease, affecting to 59% of the population, followed by respiratory disease, skin disease, oral disease, et al. The frequency of oral disease increased gradually, with the first peak at 26-30 years old. Ophthalmic and Ear-nose-throat diseases increased rapidly over 40 years old. The frequencies of above diseases were higher in submarine of Fleet B than that of Fleet A (P<0.05). In Fleet A, the frequencies of influenza and diarrhea in submarine were higher than those in surface fleet (P<0.001). The corps with low psychological self-evaluation suffered more diseases than those with high evaluation (P=0.04). Conclusions: Fleets in different latitudes exhibited different disease frequencies. Submarine force was more susceptible to infectious disease than surface fleet possibly due to the closed environment. High effective medical care should be given according to the age threshold of 25 and 40.


Introduction
Navy corps is supposed to be the major defensive support for costal countries. Many missions of Navy corps are implemented either offshore or far sea. The health states of the corps, working and living in such an environment different from inland, should be given the special concern. Neuromusculoskeletal injuries were considered as one of the largest detractors from military readiness and causes of disability in the military, and early physical therapists intervention can prevent and rehabilitate injuries and promote human performance optimization by a ten-year review [1][2] . Numerous evidence suggested the link between deployment and development of chronic lung disease 3 .An Acceptance and Commitment Therapy (ACT)based program called Mindfulness for Pain and Performance Enhancement (MPPE) 4 , was proved to help recruits effectively handle pain and improve their physical performance. The impact of psychological stressors should also be addressed within naval service populations 5 . Tele-critical care (TCC) has recently been taken as a effective means to extend intensivist expertise and to improve outcomes of critically ill patients 6 .Several evaluation systems including NPS(U.S. National Park Service) 7 and high-delity medical simulation scenario 8 were successfully applied to assess the medical demand of Navy and the of medical training.
In recent years, Chinese Navy has developed and undertaken multiple international ocean navigations, including Somalia escort, Gulf of Aden escort, multi country joint naval training, including RIM of the paci c (RIMPAC), and many kinds of military visits. The navy corps routinely takes a long journey, exposes to the complex climates and environments, and therefore may be stressed a lot from physical and psychological problems. In addition, spectrum of disease and life style in China especially for young people has been changed a lot [9][10]

Questionnaire and epidemiological investigation
A self-reported questionnaire was designed by three investigators (XT, YD, HZ). After two rounds of presurvey, nal version of the questionnaire was determined and included the following three main parts (Appendix A). The demographic characteristics such as age, gender, service years in the Navy was recorded in Part one. Part two was composed of two multi-choice questions(Q1, Q3), eight single-choice questions (Q16-Q23) and one essay question (Q24), in which basic physical and psychological problems were acquired. Part three was composed of seven multi-choice (Q2,Q4,Q5,Q8,Q10,Q12,Q13), ve singlechoice (Q6,Q7,Q11,Q14,Q15) and one essay questions (Q9), in which the potential risk factors related to the health, hygiene consciousness, medical needs were investigated. Because the questionnaire was selfadministered, all the questions were listed according to the logical order so that those pulled were easy to follow. Except for the questionnaire, 20 Navy medic in Fleet A were personally interviewed on the current measures of healthy and epidemic prevention, future demand of Navy hygiene and health care workers.
All procedures performed in our studies involving human participants were in accordance with the ethical standards of the Institutional Ethical Review Board of Naval Medical University (reference number: TMEC2014-002) and with the 1964 Helsinki declaration. And verbal consent of the respondents was obtained before the interviews were conducted.
The surveyors were trained according to the standardized protocol. The investigation began in Sep 2016 and last ve days. The primary data was double checked by the two different entry personnel. The missing items were completed or deleted as appropriate. The response rate of each question was calculated.

Statistical analysis
Comparative analysis was performed between submarine force and surface eet, or between Fleet A and Fleet B. The comparison of categorical data was performed using Chi-square test. The quantitative data was analyzed using Student t test. All statistical tests were two-sided and conducted using Statistical Program for Social Sciences (SPSS 21.0, Chicago, IL, USA). A P-value of <0.05 was considered as statistically signi cant.

Results
Self-assessment of physical state of Navy corps The self-reported rates of common diseases in two eets were sorted in descending order as following: muscle and skeletal system disease, respiratory disease, skin disease, oral disease, digestive disease, and ophthalmic and ear-nose-throat diseases. Such a trend was also found in the surface eet or submarine force of Fleet A, or Fleet B. As to the submarine branch, the self-reported rates of all the common diseases were signi cantly higher in Fleet B than Fleet A (Table 1). In Fleet A, skin and respiratory diseases were signi cantly higher in the surface eet than that in the submarine force, and other common diseases exhibited similar trend without signi cance.
The self-reported rate of each disease was obviously increased with the age (Figure 1). The frequencies of digestive, respiratory and skin diseases were rising steadily. Muscle and skeletal system disease kept about the frequency of 60% under age 30, while over age 30, the frequency approximately increased up to 80%. Two peaks of the frequency of oral disease occurred in the age group of 26-30 and 36-40, respectively. The self-reported rate of ophthalmic and ear-nose-throat diseases increased a lot over age 40.
We further investigated the self-reported rates of infectious diseases that the corps had in the past six months. Generally, the most common infectious diseases were in uenza and diarrhea with the frequencies of 65.1% and 48.6%, respectively. Moreover, the corps with age of 21-25 was high risk group predisposed to these two common diseases, in which the frequencies of in uenza and diarrhea were 42.4% and 46.2%, respectively. Other infectious diseases according to the frequency in descending order were malaria, hepatitis, and pulmonary tuberculosis. The self-reported rates of infectious disease in the submarine force of Fleet A and Fleet B were similar (P>0.05 Figure 2). In Fleet A, the frequencies of in uenza and diarrhea in the submarine force were much higher compared to that of surface eet (P<0.001). This indicated that airtight cabin of submarine force can effectively increase the possibilities of pathogen transmission. Specially, Fleet B, contributing 70% to the total malaria patients, reported more patients than the submarine force of Fleet A (2.7% (7/264) vs 1.3% (1/76), P=0.690).

Self-assessment of psychological health
The psychological problems were reported in 47.3% of the corps, and the frequency was de nitely increased with the age. In the age group of 21-25, the reported frequency reached to 47.1%. The age group of 31-35 took much higher reported rate of 62.5%. All the personnel with the age of 41-45 reported psychological problems, though it was partially because of small sample size. The total of 10% of the soldiers reported to be ever got psychological problems. Although the rate of ever being sick with psychological problems in the submarine force of Fleet A was higher than that of Fleet B (16.7% vs 8.1%, P=0.028), the self-reported rate of the existing psychological problem of the former was much lower than that of the latter (29.5% vs 52.6%, P<0.001). This indicated some intervention in Fleet A may be responsible for this change. Furthermore, in Fleet A, the frequency of the existing psychological problem of the submarine force was signi cantly lower than that of the surface eet (29.5% vs 46.8%, P=0.019).
The events re ecting current psychological state were also exhibited in Table 1. Over half of the personnel suffered from trouble sleeping. Of those with the existing psychological problem, 70.15% was reported to have trouble in sleeping. More "trouble sleeping" (56.3% vs 38.5%, P=0.007) and "being awakened by horrible dream" (48.7% vs 33.3%, P=0.02) existed in Fleet B than that of the submarine force of Fleet A. In Fleet A, more "trouble sleeping" (56.4% vs 38.5%, P=0.037) while less "being worried about training injury" (48.1% vs 53.9%, P=0.004) were signi cantly reported in the surface eet compared to the submarine force.

Risk factors related to health problems
To further explore the risk factors related to the health of the corps, the potential items related to living condition, working environment, living habits and health education were listed ( Table 2). Closed working condition of long term, humid climate of costal location, heavy maintenance of vessels were considered by the submarine force as the top reasons to cause disease. Whereas in the surface force, closed working condition of long term, humid climate of costal location, poor dietetic hygiene and shortage of fresh water supply were the top reasons. Except for the items in the questionnaire, the surface eet made supplementary items affecting health: 1) no time to be hospitalized due to busy work; 2) too short time of exercise; 3) only physical examination without further therapy;4) unquali ed fresh water and tableware. Others 32.9 8.9 15.9 11.0 The corps of different age group complained different top risk factor. Heavy maintenance of vessels was taken as the top factor to affect health by age group of 16-20 and 31-40, while closed working condition of long term was the top factor by age group of 21-30 and overloaded training was the top factor by age group of 41-45. About 77% of the corps considered both the working and living conditions should be improved.
The unhealthy living habits reported was ranked by smoking, alcohol intake, drinking strong tea, chewing arecas, biting nails, which were all traditional unhealthy habits in modern China 11 ( Figure 3A). Such a trend was similar either for the surface eet or the submarine force. Fleet B reported signi cant higher frequency of drinking alcohol than the submarine force of Fleet A (58.0% vs 34.8%, P=0.01). We also investigated the approaches the corps acquired the knowledge of health care. The most popular way was medical doctors and nurses either for different eets or branches, followed by network, families and friends, professional books, and popular magazines ( Figure 3B). In addition, about 76.1% of the corps considered it necessary to set up the specialists including otolaryngologist and dermatologist when executing a mission on the sea. Above indicate that health workers including the specialist played an important and irreplaceable role to perform health care and health promotion for the Navy.
To investigate the unexpected factors which may affect performing medical service, the total of 20 Navy medics in Fleet A was personally interviewed, including 10 had bachelor degree and 10 had senior college degree. The most serious problem reported is the members can't be quickly adaptable to their job and working environment after graduation, which was mainly because their major was clinic medicine other than family medicine. Some of the medics just graduated even could not succeed in performing intravenous injection although they might join the complex surgery in the hospital during their intern. So the corps preferred nurses to young medical doctors for medical need, which made the medics frustrated for a long time even suffered from mental disease at the end. Thus family doctor was the rst urgent medical need for Chinese Navy. The second problem is the air pollution caused by disinfection of ultraviolet radiation, especially in the con ned space without good ventilation like the submarine. Most of the vessels made by iron and steel also limited the extensive application of the effective disinfector acetic acid peroxide.

Discussion
In this paper, for the rst time, we exhibited the major spectrum and frequencies of diseases of Chinese Navy in different sea areas, and further compared the health state and related risk factors in different eets and branches including submarine force and surface eet. The muscle and skeletal system disease, affected up to 59% of the population, was the top one complained by the Navy despite of different eets or branches 12 . The age was one of the most important risk factors affecting physical health 13 . As Figure 1 shown, 25 and 40 were considered as the age boundaries stratifying service time into three stages: Stage I: ≤25 yrs; Stage II: 25 yrs and 40 yrs; Stage III: ≥40 yrs. In Stage I, muscle and skeletal system disease, respiratory disease and skin disease were the main physical problems. Stage I was also susceptible to the infectious diseases. Except for these diseases, oral disease increased a lot since Stage II. The self-reported rates of ophthalmic and ear-nose-throat diseases increased rapidly since Stage III. The otolaryngologist and dermatologist were supposed to go along with the corps when executing the mission on the sea 14 . Therefore medical needs should be met with the age and mission related issues by utilizing multilevel prevention 15 . Although the physical health state was not con rmed by the physicians in this paper, the self-assessment seemed to provide more valuable information in a sense 16,17 . Most of the Navy corps is young person and the naval service was of high density, so they prefer holding back the discomfort to seeing a doctor, especially for the chronic non-communicable diseases 18 . Therefore the self-assessment beyond clinical diagnosis may re ect the real world and urgent medical needs more extensively 19 . However, the evaluation on physical state in our study was somewhat super cial as to the Navy corps. Physical tness including endurance, power, agility should also be assessed [20][21] .
As known, not only the physical state but also psychological health affects the performance in military occupations [22][23] . It has been suggested that the research on the Navy, Army, Air force should be treated as separate entities 19 . Our investigation indicated psychological problems were the very common issue in the Navy 24 . Moreover, the submarine of Fleet B complained more psychological problems than that of Fleet A, including trouble sleeping, horrible dreams in the last six months, being worried about military training injury, being affected by sailing over 7 days, being lack of con dence with the mission, low selfevaluation on psychological health. All these clues indicated that the psychological state of different branches of Navy corps were different 25 , although they shared similar environment of submarine. Fleet B reported closed working condition of long term whereas the submarine force of Fleet A took heavy maintenance of vessels as the top reason to cause disease (Table 2), which indicated poor physical state of Fleet B may be due to the tasks with longer term. Furthermore, the submarine force of Fleet A reported more rates of ever being sick while less rates of existing psychological problem compared to that of Fleet B. According to the survey on the medic of Fleet A, the psychological guidance was performed regularly, including publicizing psychological health knowledge, outdoor expend training and group counseling. Thus the early psychological guidance in the Navy was suggested to be set up systemically and individually according to the different military branches and missions. Additionally, the psychological status was highly consistent with the related events including trouble sleeping in our investigation, although system checklist-90 (SCL-90), the classic questionnaire, was not applied to evaluate the state of the corps. For example, over 70% of the corps with existing psychological problem complained trouble sleeping, which was coincident with other studies 26 . That over half of corps was trouble in sleeping in our study was also consistent to the study of sleeping deprivation on US.Navy 27 .
Although both Fleet A and B have submarine branch, the self-rated health of Fleet B was relative poorer than that of the submarine force of Fleet A. The self-evaluation score was correspondingly lower in Fleet B than that of Fleet A. Smoking was reported more in Fleet B than the submarine force of Fleet A. These clues partially con rmed that military service could in uence health via health behavior 28 and might heighten the risk of initiating smoking 29 . Nevertheless, under such a limited space for physical activities, no sunlight exposure and noisy environment, submariners are the high risk population susceptible to the common diseases and infectious diseases, of which medical needs should be assessed comprehensively and independently 30 . The epidemic of malaria by self-report in our study was more serious than US.Navy and Marine corps from 2013 statistics 31 , although the epidemic of malaria in China decreased in these years. Both navies either engage in the military missions or supply the aids in malaria-endemic regions.
Thus quarantine restriction and isolated therapy was supposed to be the key issue contributing to the gap of malaria epidemic between Chinese Navy and US.Navy.

Conclusion
Fleets in different latitudes exhibited different frequencies of diseases. Submarine force was more susceptible to infectious disease than surface eet possibly due to the closed environment. The detail medical service for submarine force of Navy should be special on control and intervention of infectious disease. High effective medical care, including routine physical examination, rehabilitation and the support from specialists when executing long-term navigation, was supposed to be given separately according to the age threshold of 25 and 40. The physical health was closely correlated to the psychological health. Family doctor was the rst urgent medical need for Chinese Navy.