Analysis and determinants of Chinese navy personnel health status: a cross-sectional study

Military operations and related tasks require military personnel to maintain optimal physical and mental health fitness. Despite significant progress in defense technology, there remains a demand for high levels of physical fitness and physical functioning capacity [1]. Despite the younger average age of Chinese navy personnel in comparison with general population, there is still a need to explore their health behaviors and modifiable risks, and to understand levels of physical functioning and factors associated with higher levels of fitness [2].

Many behavioral factors or health habits, such as cigarette smoking, alcohol consumption, physical exercise, weight gain, eating habits and hours of sleep, were significantly associated with physical well-being and overall health. Among these factors, smoking and drinking are more prominent factors in the military population reported by many studies [2, 3]. For example, Kaly et al. [3] and LaBrie et al. [4] reported that active duty military personnel drink more heavily than their civilian counterparts and also engage in other health risk behaviors such as smoking, substance abuse and risky sexual behaviors. A survey on the alcohol drinking habit of Chinese naval pilots by Zhang et al. [5] reported that 74% of the survey population was drinking, and most of them started using alcohol after they joined the army, thereby implying that this can obviously affect flight safety and increase the risk of accidents. Specific smoking has been reported to be a major issue due to its high rate, which eventually impairs the troop readiness and productivity and increases the medical and training costs [6, 7]. An investigation on smoking behavior of Chinese naval aviators showed that total smoking rate was about 61%, and of which 42% smokers suffered from one or more smoking-related diseases [8]. However, above two studies only focused on naval aviators in China, and little information is known about the prevalence of smoking and drinking in all branches of Navy. Moreover, other health risks including weight gain in military personnel as reported by studies in other countries, primarily due to poor dietary patterns and sedentary lifestyles in some cases, have been strongly linked with increased prevalence of acute and chronic illness, injury, healthcare costs, disability and absenteeism [9‐11]. One domestic study described overweight or obesity along with other factors to be associated with obesity-related disorders such as hyperlipidemia and hyperuricemia in Chinese naval aviators [12]. However, no report was found regarding the association between weight gain and health status in Chinese naval personnel.

Moreover, the contextual factors affecting physical and mental health among general as well as military population have been well studied. Previous studies have indicated that demographic factors such as social support, marital status, household income and occupation significantly affect health outcomes [13]. For example, social support from financial assistance (e.g., household income), companionship and so on, shows a positive relationship with good perception of physical health and improving subjective well-being [13]. In addition, Smith et al. [1] found that being married and having a higher military rank are independently associated with more favorable health status. Other studies have indicated that military deployment is associated with adverse health related outcomes, including high-risk behavior and psychological morbidity from both real and perceived exposure [14, 15]. But, there has been little information about the exact relationship between the deployment status and self-rated health in the Chinese navy personnel.

In summary, it is important to understand the various demographic and behavioral factors adversely affecting health. This would subsequently lead to the development of comprehensive and cost-effective intervention programs for health promotion. Therefore, based on previous studies, we proposed the following hypotheses: (1) The health status of navy personnel is different from that of the general population, (2) certain sociodemographic factors and health hazard behaviors could influence their health status, and (3) military deployment is related to their health outcomes. Thus, in this study we investigated the health status of Chinese navy personnel, and explored the relationship between health status and sociodemographic factors, health-related behaviors and deployment status in a military cohort. We believe that these findings would be helpful in understanding the health of Chinese navy personnel, and can be useful in multiple ways like: (1) they can provide an indication about the quality of life of Chinese navy personnel, (2) specific information of health influencing factors can provide reference for their health education and health interventions, (3) these population-based results can also be used to compare the health of personnel within the navy or army or air force or with Chinese general population, (4) these results can also serve as a reference for exploring the health of particular sub groups within the military, such as the marines or coast guard, (5) the health status information can also provide a useful and comprehensive assessment of the health characteristics of these navy personnel and will be helpful in improving the health care delivery systems, along with their utility in the development of health promotion efforts.

This cross-sectional study has investigated various determinants affecting the health status of Chinese navy personnel, using a specific population sample with an emphasis on health related behavioral factors. To our knowledge, this is the first study in China, to assess the navy personnel health status based on PCS and MCS scores, and their relationship with different health risk behaviors. This study would eventually have important implications for China’s public health system, especially for the health of Chinese military personnel.

In the present study, approximately 76% of the participants reported good health, indicating that most of navy soldiers and officers feel better about their health status. This information was consistent with study by Smith et al. [25], which showed that most respondents (69.8%) of US Navy and Marine Corps personnel reported their health as being very good or excellent. However, in the 8 domains of HRQOL, navy personnel had lower scores from 5 to 18 points than the general Chinese population aged 14~ 44 years, indicating that HRQOL in these domains was less favorable [26]. In comparison with US military samples of Millennium Cohort Study (where navy population accounted for 23.6%), our study participants showed 6 subscales that were lower from 4 to 13 points except for BP and VT subscale scores which tended to be better than that of US military samples [27].

Based on SF-36 V evaluation results, we observed that the PCS score was above the Chinese population mean of 50, indicating that the navy’s physical health status was better than general Chinese population. Moreover, the MCS score was about 8 points lower than general Chinese population. The reason may be the job environment and job characteristics that navy officers and soldiers confronted were under greater psychological pressure, and they could have higher probability suffering from mental disorder in comparison with people of similar age in Chinese population [28, 29]. Although the MCS score of the navy at the survey time was in the normal range considering their occupation, their mental health status may need extra attention to meet the requirements of modern military construction and high-tech war in the future.

Furthermore, in the present study we have identified relationship through multivariate model, of number of sociodemographic and military characteristics, including age, educational attainment, marital status, race, household income, residential location, rank, duration of military service, with health status. The results showed that the length of service and household income were independently associated with physical and mental health status, respectively. Importantly, we noticed that participants with long service time had lower PCS scores, thereby suggesting more physical health problems in these participants. The result was in line with the studies of Tian et al. [30] and Smith et al. [1]. Tian et al. found that longer military service correlated with lower score of physical functioning (p<0.001), while Smith et al. found that military members with longer lengths of service had less favorable physical health (p<0.05). Our finding is also independently confirmed with the observation that longer service times showed association with self-rated less than good health (poor). This could be attributed to the fact that navy personnel with long military service completed more tasks of combat training mission, and long period also exposure them to various health hazards and intense and stressful environments, thereby resulting in greater risk to their health.

Interestingly, the participants with higher household income displayed higher MCS score, representing more favorable mental health status than soldiers with less household income. Feng et al. [31] reported that family financial difficulties influenced the mental health status of navy officers and soldiers. The findings of our study are basically in agreement with previous studies. The reasons may be related to more psychological pressure on navy personnel with lower household income. If psychological pressure could not be alleviated, it would probably lead to poor mental health status. Thus, this observation in our study will have important implication for health professionals to identify those personnel, who are most likely in need of help, and eventually allocate the health care resources, accordingly.

Additionally, higher rates of health risk behaviors such as cigarette smoking and alcohol misuse among veterans have been reported in comparison to non-veterans in various studies [2, 3]. The smoking prevalence estimated by our study in navy personnel was lower than the civilian rate of 59.7% as reported by Xu et al. in 2010 [32], but it was significantly higher than prevalence of current smoking (17.9%) of navy personnel in Sri Lanka [33] and 2005 estimate of US Navy soldiers (32%) [34]. However, the navy personnel had significantly higher drinking rate than general population (39.6%) as reported by Ma et al. [35] in 2007. LeardMann et al. [36] documented that 32.6% of US Marine Corps recruits were high-risk and potentially problematic drinkers. Comparably, our study also showed that nearly 47% of the participants in our study have experienced binge drinking. The studies by Widome et al. [2] and Ryan et al. [37] have demonstrated that military personnel are more likely to have higher BMIs, and thus would be categorized into the overweight category. Similarly, our study observed that about 26% of the participants were overweight, which was higher than the overweight rate (22.8%) in Chinese population over the age of 18 years, as reported by a national survey in 2005 [38]. There are indications about overweight or obesity association with long-term drinking, smoking, and lack of exercise, and it has been observed that navy personnel while on duty have irrational dietary plans. For example, when the navy personnel are on duty at sea, they consume more red meat and processed meat, but fewer fruits and vegetables and also no engaged in regular exercise routine than during other time [39, 40].

Finally, our study also examined the relationship of health status with health-related behaviors, BMI and deployment status of navy members. Our analysis identified that binge drinking and BMI were independently associated with both physical and mental health status, whereas frequent drinking was independently associated only with physical health status outcomes. The participants with higher physical and mental health scores were observed to be involved in significantly less risky behaviors like binge drinking, regular drinking, and BMI, and reported significantly good self-rated health. It again confirmed that binge drinking and BMI were associated with self-rated fair/poor general health. Overall it can be deduced that increased awareness about the health hazards of alcohol misuse should be emphasized and some alcohol reduction strategies for health promotion should be introduced. Moreover, effective measures on modifying BMI in military need to be carried out and implemented. Relevant departments need to invest the necessary funds to improve the living facilities and environmental conditions of the troops, especially provide adequate fresh vegetables and fruits to soldiers on duty or training at sea.

Although deployment status and smoking were significant predictors in the preliminary variance analysis model, they did not remain significant in the final analysis. This observation was contrary to the results of studies by Ryan et al. [37] and Robyn et al. [15] and Jahnke et al. [6]. Ryan and Robyn suggested that the psychological and physical effects of deployment may have a greater impact on health. At least some military activities might be resulting in mental and physical health deterioration. In a population-based study conducted on U.S. Marines, Robyn et al. [15] found that significant number of individuals in the war-deployed cohort were likely to have a posttraumatic stress disorder (PTSD) diagnosis than individuals in the non-war-deployed cohort (p<0.01). The HRQOL reported by these veterans has also been shown to be significantly less favorable [41]. However, in the present study, deployment status had no significant effect on either the health scores of PCS, MCS or self-rated general health. This difference could be attributed to the fact that the participants in their study were mainly involved in war-related military operations, such as Gulf War, Vietnam War and Operation Iraqi Freedom, while Chinese navy personnel has spent relatively little time waging conventional battles and has only engaged on numerous non-war military actions, for instance, peacekeeping operations, earthquake relief actions, security operations.

The study by Jahnke et al. [6] analyzed the impact of tobacco use on military health and readiness. Interestingly, we observed no significant association of smoking with PCS and MCS scores in the final model, and this observation was consistent with the finding by Darviri et al. [42], who also showed that smoking did not exhibit significant association with self-rated health. Again, this could partly be due to the fact that (1) navy soldiers are young, and the disease caused by smoking takes a long time to show; and (2) previous study have shown that smoking is considered to be an accepted stress relief method. However, further studies would be required to help confirm the specific reasons.

Our study has certain limitations. Firstly, it is a cross-sectional study and thus we cannot make definitive conclusion about the observed associations. Secondly, weight was recorded in a self-report form and was likely to be underestimated. This would result in underreporting of BMI. Thirdly, there were 117 participants who did not provide complete information. However, their characteristics were not significantly different from those included in the analysis, and non-responders are not in high number. Thus, we expect that exclusion of these non-responders did not influence the statistical analyses. Moreover, sample size was not determined, since it could meet the requirements for ANOVA and regression analysis.

In conclusion, our study provided the preliminary information on the health status (based on physical and mental scores) and various factors affecting it in Chinese navy personnel. Our study demonstrated that some sociodemographic and health-related behavioral factors such as, length of service, frequently drinking, binge drinking and BMI, influence the health status. This initial baseline information would be helpful for designing the health promotion strategy for military personnel in China and assisting health policy makers in preparing for appropriate health, nutrition, occupational environment, and social support guideline for the Chinese navy personnel. However, further research would be required by including large data points to specifically focus on the different health risk factors, and evaluating the dynamic changes in the health status. These interventions will definitely help to improve the overall health of the navy personnel and subsequently improving their combat capability.