Abstract

Introduction

Determining sleep quality and duration and the factors influencing the quality of sleep among the military is crucial for designing effective interventions. Given the strict and demanding nature of the military setting, it becomes essential to explore factors impacting sleep quality in such a context. Additionally, research in the Middle East and among females on this subject is scarce. This study aims to investigate sleep quality and different sleep-related variables such as sleep duration and sleep hygiene practices in addition to the correlates of sleep quality among recruits.

Methods

This is a cross-sectional study that included 178 (Mean age鈥�=鈥�19听years) military recruits during their basic training at two medical military colleges in Jordan. Sleep quality and sleep hygiene practices were assessed using the Pittsburgh Sleep Quality Index (PSQI) and Sleep Hygiene Index (SHI) respectively. Physical activity and dietary behaviors were measured using the Arab Teens Lifestyle Study (ATLS).

Results

The majority of recruits demonstrated poor sleep quality (80%) and suboptimal sleep hygiene practices (mean SHI鈥�=鈥�21) with significantly poorer sleep hygiene practices among male recruits. The average duration of actual sleeping hours per day was around 6听h (卤鈥�2.3 h). Multiple regression analysis showed that age and SHI score were positively associated with the global sleep quality score (PSQI), while sleep knowledge score was negatively associated with sleep quality among the whole sample (adjusted R²鈥�=鈥�0.11). However, the association between sleep hygiene practices and sleep quality was not modified by gender.

Conclusions

Jordanian military recruits on average had short sleep duration and poor sleep quality. Results showed that better sleep hygiene practices (especially among women) and more sleep knowledge (particularly among men) were associated with better sleep quality. Interventions that use cognitive and behavioral change methods to promote sleep hygiene and improve sleep knowledge are recommended to improve sleep quality among military recruits.

Introduction

Poor sleep health is an underrecognized global public health problem that is strongly associated with morbidity and mortality [1]. Accumulative evidence suggests that insufficient sleep increases the risk of obesity, metabolic syndrome and cardiovascular diseases [2, 3]. Moreover, sleep disruption is also consistently linked to psychiatric symptoms and diseases such as post-traumatic stress disorder (PTSD), substance abuse, and suicidal ideation [4].

Sleep has a significant impact on military personnel as well [5]. A study which was conducted in the U.S. found that short sleep duration (<鈥�5听h) was reported by around 42% of active-duty military personnel [6]. Another study that included around 2000 service members across all branches of the U.S. armed forces found that approximately 18% of the military service members reported using sleep medication [7]. Moreover, evidence showed that military personnel with insomnia symptoms had more absence days from work, poorer self-rated health and a higher probability of discharge from the military [8]. Inadequate sleep among military personnel has also shown to impair attention, judgment, responsiveness, decision-making, and operational readiness [9, 10]. For instance, a study of U.S. Navy personnel who participated in Afghanistan found more accidents among those with fewer sleeping hours [11]. Although studies included both males and females, they seldom included separate results for genders.

Military leaders are becoming increasingly cognizant of the importance of sleep for sustaining performance, safety, and health [5]. However, translating this expanding appreciation for the importance of sleep into practice during military operations constitutes a significant challenge. The military lifestyle often involves stressors like 24-h operations, deployment that involves changes in the sleeping environment, noise, and shift work, hindering restorative sleep [7].

Recruits during basic military training are at high risk of poor sleep health due to the nature of rigorous and unique training schedules [12]. Two studies on basic military training recruits in the US and Australia found reduced sleep duration and quality compared to baseline levels [12, 13].

Sleep quality is a better predictor of health, cognitive, and physical performance and more comprehensive than sleep duration alone [14, 15]. Understanding sleep health, including quality and duration, is essential before developing interventions to improve sleep quality in the military. In addition, it is crucial to assess the etiology of poor sleep quality and then potentially change military recruits鈥� sleep habits throughout the military training [12].

Sleep hygiene is a set of behavioral and environmental recommendations that promote healthy sleep [16]. Recommendations include maintaining a regular sleep schedule, limiting caffeine and alcohol before bedtime, and exercising regularly (but not before bed). Additional suggestions are reducing noise, winding down before bed, and managing stress. A systematic review found that sleep hygiene interventions generally improved sleep quality among college students [17].

Knowledge of sleep issues may influence sleep, as research showed and association knowledge and health behaviors such as physical activity and diet [18]. Studies that assess sleep knowledge focus on different aspects of sleep knowledge such as basic sleep principles, sleep architecture, the effects of drugs and alcohol on sleep and common sleep illnesses (e.g., insomnia) [19]. Sleep knowledge assessment can also include the health impact of inadequate sleep [20]. Gallasch et al. conducted a cross-sectional study among civilians. It examined the relationship between sleep knowledge (related to sleep hygiene and behavioral treatment), sleep quality, and sleep practices. The study found no significant association between sleep knowledge and sleep quality after adjustment for age and gender [21]. The study suggested that the relationship between sleep knowledge and sleep quality was mediated by sleep hygiene practices. This indicates that poor sleepers may not implement their knowledge to adopt appropriate sleep hygiene practices as they may find them ineffective or difficult to maintain.

Sleep quality has been promoted within the context of the transtheoretical model [22]. The model views behavior, such as sleep practices, as a process with five stages: pre-contemplation, contemplation, preparation, action, and maintenance [23]. Therefore, the framework suggests that individuals need to move through these five stages to achieve the desired behavioral change. Interventions use the transtheoretical model to identify the current stage of change for participants and tailor the intervention approach to achieve the desired behavioral change, such as obtaining 7鈥�9听h of sleep every day [24].

Other lifestyle behaviors and body weight can affect sleep quality in addition to sleep hygiene practices and sleep knowledge. A study with about 14,000 US Army personnel found that poor sleep quality was linked to unhealthy weight measurements, irregular breakfast intake, and insuffucient physical activity [25].

To date, a significant gap remains in our understanding of sleep quality and its associations among military recruits in Jordan and the broader Middle East. Worldwide, comprehensive evidence is scarce on the factors influencing sleep quality. Additionally, there is a noticeable absence of research focusing on sleep health among active-duty female military personnel. This creats a substantial research gap possibly due to less females joining the basic military training than males [26]. Existing studies fall short in providing evidence of whether gender differences persist when accounting for other socio-demographic and lifestyle factors [27]. Hence, there is a compelling need for further exploration of the factors influencing changes in sleep quality during basic military training, particularly when considering gender differences. We will assess gender difference especially regarding the correlates of sleep quality due to limited evidence. Such an exploration is expected to offer valuable insights into the design of military interventions that enhance sleep health and optimize the performance of military personnel.

This study aims to evaluate overall sleep health, encompassing aspects such as sleep quality, daily sleep duration, weekly nap frequency, and sleep hygiene practices. Furthermore, the study aims to explore the correlates of sleep quality among Jordanian military recruits in addition to the potential gender variations in these correlates. These possible determinants include sleep hygiene practices, sleep knowledge, age, gender, and BMI. Also, ifestyle correlates will include smoking status, screen time, physical activity, and specific dietary habits (e.g., breakfast, fruit and vegetable consumption).

Methods

Study design

The study applied a cross-sectional design following the guidelines set by the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement for reporting observational research [28]. A simple random sample was taken from two military colleges of the Jordanian Royal Medical Services in April 2022.

Participants and the military context

A total of 178 first-year military recruits actively participated in this study. One of the military colleges exclusively enrolled females, while the other included both males and females. Therefore, the sample consisted of a larger number of females (127) compared to males (51). Eligibility for admission to medical military colleges in Jordan is based on individuals being 18鈥�20 years old, single, possessing a high school diploma, and meeting military medical and fitness criteria. These recruits undergo 2鈥�4 years of training to qualify as military medical personnel, including roles such as nurse and physiotherapist. Typically, young adults pursuing this training spend their weekdays within the military accommodation and return home for the weekend. The weekly military regimen involves daily physical activities like aerobics and military exercises such as marching, alongside medical training and lectures. Both male and female recruits adhere to the same daily schedule. The military provides three nutritionally balanced meals, designed by licensed dietitians in the military kitchen. Additionally, recruits have the choice to purchase snacks from nearby canteens. Regarding sleeping arrangements, recruits are permitted to rest from 10 p.m. to 5 a.m., with approximately six recruits sharing a room. Moreover, naps are allowed for recruits at the mid of the day.

Procedure

Recruits filled out paper-based questionnaires in Arabic, in a large lecture hall. We prioritized ensuring that participation was voluntary and anonymous, with recruits fully aware of the study's objectives and providing written consent. The majority of recruits (95%) agreed to take part, and the average completion time for the questionnaire ranged from 20 to 30 min.

Variables and measurements

The data collected for the present paper were part of a bigger study that gathered data on several health-relevant behaviours (see our last publication on the motivation determinants of physical activity [29] and for a comparable study in the United Arabic Emirates on the correlates of dietary behaviours [30]). Data for the present study was collected from military recruits by asking the participants to complete the Sleep Hygiene Index (SHI) [31], the Pittsburgh Sleep Quality Index (PSQI) [32] and the Arab Teens Lifestyle Study (ATLS) questionnaire [33]. We also added three questions related to sleep knowledge which are mainly related to the negative consequences of not sleeping the recommended hours. In addition, one question was added related to the stage of change of sleeping 7鈥�9 h [22]. Moreover, self-report data on smoking status, weight and height were collected besides sociodemographic information such as age, sex and place of residency.

Sleep Hygiene Index (SHI)

The SHI is a self-report scale developed by Mastin et al., comprising 13 questions, to evaluate the frequency of engagement (ranging from always to never) in various sleep hygiene practices such as daytime napping, tobacco consumption, and screen usage before bedtime [34]. Each item was rated on a five-point Likert scale (ranging from 0 [never] to 4 [always]). The total scores ranged from 0 to 52. Higher scores indicate more maladaptive sleep hygiene practices. Test鈥搑etest reliability of the original questionnaire was evaluated with a sample of approximately 600 subjects and revealed consistent and stable reliability over the testing period (Pearson r鈥�=鈥�0.71) [34]. Evidence for the construct validity was also found as the SHI score was strongly correlated with all features of inadequate sleep hygiene and significant daytime sleepiness demonstrated by the Epworth Sleepiness scale [34]. In our study, an Arabic-validated version of the SHI was used [35] and showed an internal consistency (Cronbach's alpha) of 0.65.

The Pittsburgh Sleep Quality Index (PSQI)

PSQI is a widely used validated scale, consisting of 19 self-rated items, that differentiates 鈥減oor鈥� from 鈥済ood鈥� sleep by measuring seven domains: subjective sleep quality, sleep duration, sleep latency, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction over the last month [36]. The scoring of each domain is ranging from 鈥�0鈥� to 鈥�3鈥�. The global PSQI score is calculated by summing the seven domains. So, the total score of global PSQI ranges from 0鈥�21. A total score of 5 or greater indicates poor sleep quality, while a score below 5 suggests good sleep quality [32]. We used an Arabic-validated version of the PSQI with a convergent validity supported by correlation with insomnia severity index (r鈥�=鈥�0.76) and acceptable internal homogeneity and consistency as demonstrated by Cronbach鈥檚 伪鈥�=鈥�0.65 [37]. Our study showed that the internal consistency of this Arabic version of the PSQI (Cronbach's alpha) was 0.74. The actual sleeping hours per night was assessed by one of the PSQI questions.

Sleep knowledge, stages of change items and number of naps

Three questions were used to assess sleep knowledge. For instance, one question assessed the extent to which participants thought that sleeping less than 6 h sleep a day can lead to severe health problems, such as metabolic disorders and cardiovascular disease. Each item was rated on a five-point Likert scale (ranging from 1 [totally disagree] to 5 [totally agree]). Question scores were summed, so higher scores indicate higher agreement and better knowledge. One item addressed the participant鈥檚 stage of change regarding the intention of sleeping the recommended hours according to the transtheoretical model [38]. Participants were categorized in one of the five stages of change according to their answers. For instance, those who were not considering sleeping the required hours 鈥淚 have not even considered sleeping 7 to 9 h a day鈥� were in the pre-contemplation stage while those who slept the recommended hours for the last 6 months were in the maintenance stage. Additionally, we added one question related to the number of naps taken per week.

The Arab Teens Lifestyle Study Questionnaire (ATLS)

The ATLS questionnaire is a standardized and validated instrument to assess physical activity levels and other lifestyle behaviors such as nutritional and sedentary behaviors among Arabic adolescents. The evidence of the convergent validity of the questionnaire has been provided by the questionnaire developer [33]. Regarding physical activity, the questionnaire collects complete information on the frequency, duration, and intensity of various activities during a typical week. Moreover, the questions cover different domains such as transport, the household, fitness (e.g., calisthenics) and sports activities (e.g., swimming).

The total Metabolic Energy of Task (METs)-min /week is a standardized metric that represents the total energy expenditure during the week by multiplying the intensity of each exercise by the time spent on the exercise and frequency per week. There are three categories for physical activity levels according to the total METs/week: low, medium and high. The inactive level is assigned for those with less than 600 METs-min/week; while the minimally active is for those with 600鈥�1499 METs-min/week and finally the highly active level for those who perform 1500 or higher METs-min/week [39].

Ten questions assess different healthy and unhealthy dietary behaviors by asking participants how many times per week they consume breakfast, vegetables, fruit, milk/dairy products, donuts/cakes, sugar-sweetened drinks, sweets and chocolates, energy drinks, and fast foods. Subjects can choose answers ranging from zero intake to a maximum intake of 7 days per week [39]. The total screen time is collected by asking about different sedentary activities such as television viewing, and computer and internet use [39].

Ethics

The study was approved by the Royal Medical Services Human Research Ethics Committee in Jordan (3/2022) in accordance with the Declaration of Helsinki.

Statistical analysis

The IBM SPSS Statistics version 28 was used for all analyses. Firstly, descriptive analysis was performed for all variables including the demographic variables in addition to sleeping, dietary, and physical activity behaviors, using means, standard deviations, and proportions. Secondly, bivariate Spearman correlation analysis was conducted to assess correlations between possible correlates and the global sleep quality score as variables were not normally distributed. Potential correlates included age, BMI, total screen time, total METs-min/week, sleep knowledge score, dietary behaviors (e.g., the frequency of breakfast intake), sleep knowledge and the sleep hygiene index score. Finally, hierarchical multiple regression was conducted to assess the association between sleep quality and possible correlates. We were especially interested in whether sleep-related variables were related to sleep quality after controlling for socio-demographic and lifestyle variables. Socio-demographic variables were entered in Model 1 (age, sex and BMI). In Model 2, lifestyle variables (screen time, smoking, dietary and physical activity behaviors) were entered after adjusting for the socio-demographic variables. Finally scores on the sleep hygiene index and knowledge were entered in Model 3, after adjusting for socio-demographic and lifestyle variables. All assumptions of multiple linear regression such as multicollinearity, homoscedasticity and normal distribution of residuals were met. The selection of the best model was done according to the adjusted R² and R² change, the F statistic change, and the statistical significance of this change. All analyses were conducted for the overall sample and for males and females separately. To justify starticification by gender, sleep hygien and sleep knowedge terms variables will be created and entered in the regression model to test their association with the global sleep quality score.

Results

Participants

Table 1 presents the basic descriptive characteristics of the sample. The median age of participants was 19 years, while the median BMI was around 22 kg/m². Approximately, one-third of the participants were males and two-thirds were females. The majority of the participants (70%) were from the Royal Medical Services College of Allied Professions, 30% were from Prince Muna College of Nursing. Also, 17% of participants were current smokers. Participants鈥� permanent residence included all Jordanian governorates; 15% of them lived in Amman. A post-hoc power analysis was performed using G*Power software for multiple regression, indicating that the sample size (n鈥�=鈥�178) was sufficient, with an achieved power of 0.92. The analysis was based on an effect size of 0.15, a significance level (伪) of 0.05, and 14 predictors [40].

Table 1 Characteristics of the sample of recruits (n鈥�=鈥�178)

Basic characteristics of sleep health, stages to sleep and lifestyle behaviors

Table 2 presents the results on different aspects of sleep health (sleep quality score, sleep hygiene index, sleep duration) in addition to physical activity levels and selected dietary behaviors. Around 80% of military recruits showed poor sleep quality (PSQI score鈥�>鈥�5) with a rather high mean (PSQI score鈥�=鈥�7). Scores within the seven sleep quality domains ranged from 0.3 to 1.4 with higher scores in subjective sleep quality and daytime sleep dysfunction domains indicating reduced overall satisfaction with sleep quality. These findings suggest a potential impact of sleep on the daily lives of the recruits. Recruits had an average SHI score of 21 with significantly better sleep hygiene practices among females in comparison to males. Moreover, the most common poor hygiene practices included consuming tobacco/caffeine 4 h before sleeping, sleeping in an uncomfortable bed or bedroom and exercising to the point of sweating within 1 h before going to bed. Approximately, 65鈥�75% of recruits stated always or frequently engaging in such habits (see Appendix 1). The average actual sleep duration was approximately 6 h per night, falling short of the recommended 7 h. Almost one-third of the males report sleeping less than 5 h. Around 35% of recruits had the recommended actual hours of sleep per night with a higher percentage among females than males. Recruits reported to nap on average around 3 days per week.

Table 2 Sleep and lifestyle variables

Concerning the stages of change, 18% of recruits currently were not considering meeting the recommended sleep duration. Around 23% planned to achieve the required hours within the next 30 days, and 13% had intentions to do so in the next 6 months. Furthermore, 11% of recruits stated meeting the 7鈥�9 h of sleep recommendation for less than 6 months, whereas 25% have maintained this duration for more than 6 months. Recruits demonstrated good sleep knowledge as the mean score was around 13 (out of 15). The item reflecting the lowest level of knowledge was that insufficient sleep, below the recommended duration, contributes to serious health issues. Only 66.7% of participants agreed or totally agreed with this statement (refer to Appendix 1).

Correlates of sleep quality

Table 3 depicts the bivariate correlations between the overall score of the PSQI, and possible correlates for both men and women, and for the whole sample. The bivariate correlation analysis of the overall sample revealed that smoking, sleep hygiene and age were positively and significantly correlated with the PSQI score. This implies that recruits with older age, suboptimal sleep hygiene practices and smokers were more prone to poor sleep quality. Additionally, there was a negative correlation between the frequency of weekly breakfast intake and the PSQI score, suggesting that individuals who consumed their breakfast less frequently, generally exhibited poorer sleep quality.

Table 3 Bivariate correlations of sleep hygiene index, sleep knowledge, socio-demographic variables and other lifestyle behaviors with the overall PSQI score

Among males, the frequency of fruit intake per week was negatively correlated with the PSQI score. This means that the lower the frequency of fruit intake, the poorer the sleep quality. Age was significantly and positively correlated with the PSQI which means that the older the male recruit, the poorer his sleep quality. For females, age and sleep hygiene index scores and total METs/week were positively correlated with the PSQI. This suggests that among female recruits, those with an older age, suboptimal sleep hygiene practices, and those engaging in higher-intensity physical activity tended to experience lower sleep quality.

Regression analyses

Collinearity diagnostics showed that all VIF values were鈥夆墹鈥�3, indicating no significant multicollinearity among the predictors (see Table听4). A multiple linear regression analysis for the whole sample indicated that age (as demonstrated by model 1) was significantly and positively correlated with the overall PSQI score. Additionally, the sleep hygiene index score was significantly and positively correlated with the overall PSQI score. The sleep knowledge score also showed a positive association with the overall PSQI score, as demonstrated by model 3, even after adjusting for demographic and lifestyle variables (see Table听4). So, the older the age, the poorer sleep hygiene practices and the less sleep knowledge, the poorer the sleep quality. These variables explained 11% of the variance in the overall PSQ score.

Table 4 Multiple regression models for the correlates of the global sleep quality score for the whole sample

Sex did not significantly contribute to the regression model. Additionally, the interaction terms of sleep knowledge score and the sleep hygiene index were not significantly associated with the overall PSQI score (see Additional file 2). This indicated that gender stratification was unwarranted. However, the association between the sleep hygiene term and PSQI approached significance (p鈥�=鈥�0.06).

In summary, the multiple linear regression analysis showed that the SHI, sleep knowedge scores and age were associated with the PSQI in the overall sample.

Discussion

Our study aimed to gain insight into different aspects of sleep health such as sleep quality and sleep duration. Moreover, it assessed relevant correlates of sleep quality among first-year military recruits in two medical colleges in Jordan. The assessed correlates included sleep hygiene practices and sleep knowledge in addition to various lifestyle factors (e.g., screen time and dietary behaviors). In summary, our study showed that the majority of recruits had poor sleep quality. Moreover, on average, recruits had less than the recommended daily hours of sleep per night, with about one-third of the males reporting less than 5 h. In general, recruits had slightly poor hygiene practices, but good sleep knowledge. Better sleep knowledge and hygien practcies were associated with improved sleep quality across the entire sample. Also, older recruits had poorer sleep quality in general. Furthermore, the association between sleep hygiene practices and sleep quality was not modified by gender.

The current study found that approximately 80% of recruits had poor sleep quality. This is consistent with a cross-sectional study that was conducted among around 500 military officers and soldiers in China [41]. Our study found poorer scores in most PSQI subdomains compared to the Chinese Armed Forces study, except for better scores in sleep efficiency and sleep latency. Regarding sleep hygiene, our study showed slightly poor sleep hygiene with a mean score of around 21. A study of about 4000 students from the Saudi Medical Military College found a mean SHI score of around 25, indicating similar or worse sleep hygiene practices.

Our results showed that sleep hygiene was significantly associated with sleep quality across the entire sample. This aligns with a web-based survey of university students in Qatar, which also found an association between sleep quality and sleep hygiene practices [42].

The current study found that higher fruit intake was linked to better sleep quality among male recruits at a bivariate level. Similarly, a systematic review of 29 studies from different settings and countries reported that consuming healthy foods like fruits, vegetables, and milk intake improves sleep quality, in contrast to processed and sugar-rich foods [43].

Our study found that factors like screen time, BMI, and gender were not related to sleep quality. However, smoking was linked to poor sleep quality at a bivariate level. A systematic review of civilian university students also found that smoking, abnormal BMI, and sedentary behaviors (e.g., smartphone addiction and internet use) were associated with poor sleep quality [44].

Our findings showed that age, despite little variation in our sample. Large surveys from the UK and Korea showed that sleep quality decreases with age [45, 46], but worldwide evidence on this relationship among university students is inconsistent, especially in studies with a narrow age range [44, 47].

The current study found that awareness of the adverse health effects of short sleep duration was linked to better sleep quality among the whole sample. Wang et al. systematic review reported inconsistent evidence regarding the association between better sleep knowledge and sleep quality [44]. This can be due to that sleep knowledge alone may not necessarily alter sleep practices and because sleep knowledge is assessed in different ways (e.g., knowledge of sleep hygiene practices or sleep architecture).

However, it should be noted that the regression models explained only 11% of the variance in sleep quality. This indicates that while the factors described above contribute to sleep quality, a significant portion remains unexplained, suggesting the need to explore additional predictors.

Regarding gender differences, our study found that male recruits exhibited lower sleep quality and shorter daily sleep hours compared to female recruits, though these differences were not statistically significant. This observation aligns with findings from a cross-sectional study which was conducted in Ethiopia (although in that study a higher percentage of male had good sleep quality [48]). Several factors may contribute to the observed lower sleep quality and sleep duration among male recruits such as perceiving of less sleeping as a sign of masculinity and young male being more night owls.

This study showed that only the sleep duration subscale was significantly higher among males indicating less sleeping hours among males. A U.S. study of about 7000 university students showed that females only had better subjective sleep quality and longer sleep duration in comparison to males [49]. Furthermore, our study showed that female recruits had better sleep knowledge and sleep hygiene practices. In contrast, the Qatari study found no significant gender differences in sleep hygiene practices [42], while a U.S. survey of around 260 medical students found no gender differences in sleep knowledge [50].

Strengths and limitations

To our knowledge, this is the first study in the Middle East to evaluate various aspects of sleep health among military recruits, along with examining the factors associated with sleep quality. Furthermore, this study encompassed both male and female basic military recruits. However, it is important to highlight that this study is not without limitations. First, the cross-sectional design is not adequate to identify causality between the assessed variables and sleep quality. Second, all measurements we used including sleep quality, dietary and physical activity behaviors were self-reported, and therefore subject to several biases. For instance, the PSQI is a subjective measure of sleep quality that includes questions with a 30-day recall period and is thus subjected to recall bias [15]. It also does not differentiate between sleep quality on work days and weekends when recruits go back home and may have more sleep [51]. The sample included higher number of females than males which may lead to higher statistical power for the female sample when conducting the correlational analysis. Moreover, the sleep knowledge questionnaire was not validated due to unavailability of relevant tools. Additionally, some instruments, such as the SHI exhibit relatively borderline internal consistency, which may potentially affect the reliability of the findings. Finally, our data were collected from two medical military colleges limiting the generalizability of our results to recruits of other medical colleges and of other military branches.

Recommendations for research

In general, studies that assess the correlates of sleep quality in the military are scarce. To effectively promote sleep quality and sleep health, it is important to understand the factors that affect sleep quality. Future studies might include a wide range of relevant military determinants such as general well-being (e.g., ability to manage stress), barriers to healthy hygiene practices, and bodily pain (e.g., muscle soreness). Moreover, environmental factors such as sharing the sleeping room with others, and sleeping in a noisy room can be also relevant in such a context [52].

Larger scale studies that included a wide variation of basic military recruits (not only from medical colleges), in addition to the use of prospective study designs (e.g., cohort studies) can provide more generalizable and definite conclusions. Longitudinal study designs, such as cohort studies, can offer better evidence by identifying the population (e.g., with respect to lifestyle and sleep hygiene practices) and tracking sleep quality over time.

Further research is needed using gender balanced sample to explore possible differences in the correlates of sleep quality among males and females鈥� military recruits. Moreover, future studies need to explore sleep quality and sleep-related behaviors after finishing basic military training to monitor if there is a further decline in sleep quality after being in military service longer.

While the PSQI serves as a commonly used subjective tool for evaluating sleep quality, incorporating objective measures like actigraphy with subjective measures is an option [13]. However, these objective methods may pose challenges for military personnel due to costliness and compliance issues (e.g., wearing the device at night) [15].

Recommendation for practice

Designing evidence-based sleep interventions that consider the potential factors that affect sleep quality is the first step toward improving sleep health and sleep quality in the military. According to our results, sleep knowledge and sleep hygiene are common correlates of sleep quality among recruits. Interventions could target raising awareness about specific aspects of sleep knowledge, such as the health impact of reduced sleep. This is despite the generally good sleep knowledge identified among recruits. Our results suggest targeting poor sleep hygiene practices such as caffeine or tobacco use, exercising before sleep, and sleeping in an uncomfortable bed or bedroom. Systematic reviews provide evidence that cognitive and behavioral interventions (CBT-I) can enhance sleep quality in young healthy adults without clinical sleep disorders [17, 53].

Creating a conducive sleep environment for recruits that promotes good hygiene practices faces challenges due to the military perspective that views sleep as indulgent [54]. In the military context, sleep deprivation is often regarded as a virtue in the interest of service. Therefore, the strict schedules in training and educational settings leave limited opportunities for establishing proper sleep hygiene practices. There is a prevalent belief within the military that young individuals need to be hardened as part of their introduction into the military culture [55]. Thus, it is important to creat a military culture and policies that recognize and address the importance of sleep from a public health perspective at the macrosystem level. This would help to initiate dedicated campaigns that emphasize the importance of sleep health to overall physical readiness.

Conclusion

To the best of our knowledge, this is one of the first studies that aimed to gain insight on sleep health among male and female recruits in Jordan and the Middle East. Additionally, it aimed to assess relevant correlates of sleep quality. Our results showed that sleep hygiene and sleep knowledge were correlated with better sleep quality. Additionally, higher age predict poorer sleep quality. Future interventions should target these correlates through cognitive and behavioral change approaches that include sleep knowledge and sleep hygiene tips. Moreover, creating a supportive military environment that encourages healthy sleeping practices can improve sleep quality among recruits.