Study Design and Sample
This cross-sectional study was conducted in November 2019. The subjects of this study were 196 military women. The inclusion criteria were military women who currently served in the ROK Army with a service period within 5 years and voluntarily chose to participate in this study after receiving an explanation of the purposes and goals of the research.
Because military women work throughout the nation and the proportion of military women in each division is only approximately 5%, the survey was conducted in an online and mobile format. By cooperating with official announcements and text messages, we encouraged participation in the survey. The recruitment notice included a description of the purpose and methods of this study, the conditions for participants, the benefits and risks of this study, the discontinuation of voluntary participation, and the assurance of anonymity for the study participants.
Those who fulfilled the inclusion criteria and voluntarily agreed to participate in the study were provided a link for the online survey. Screening questions were also presented on the first screen of the online survey to ensure that participants met the selection criteria. If all criteria were met, the participant completed the survey after viewing and an explanation stating that completing the survey was considered as constitute agreement to participate in this study. All participants received a gift card for completing the survey.
The average response time for this survey was about 15 minutes. In accordance with institutional review board (IRB) approval (IRB approval number: Y-2019-0162), a protocol was put in place to ensure that the researcher was notified of responses anonymously and that the respondents’ phone numbers were not transmitted to the researcher.
In order to prevent duplicate responses from the same participants and to ensure that the survey was not distributed beyond the intended participants, researchers monitored survey participation twice a day.
The research instrument was a self-reported survey questionnaire that consisted of 116 questions, including 36 questions about HRQOL, 7 questions about physical activity, 10 questions about stress, 26 questions about attitudes to eating, 10 questions about self-efficacy, 9 questions about depression, and 18 questions about general and occupational characteristics. The original authors approved the use of the relevant tools, the validity and reliability of which have been demonstrated in previous studies.
Health-related Quality of Life: HRQOL was the dependent variable of this study. The Korean version of the Short-Form 36 Health Survey Questionnaire version 2.0 is a self-evaluation scale used to measure HRQOL , and consists of 36 items that measure eight health domains: physical function, role limitations due to physical problems, bodily pain, general health perception, vitality, social functioning, role limitations related to emotional problems, and general mental health. The score for each domain ranges from 0 to 100, with higher scores indicating better HRQOL. These domains can be categorized into the physical component summary (PCS) and mental component summary (MCS). PCS and MCS scores are represented on a standardized scale (as a T score with a mean of 50 and standard deviation [SD] of 10). The internal consistency of the PCS and MCS was quantified using Cronbach’s α, with values of 0.78 and 0.60, respectively.
Physical activity: The Korean version of the International Physical Activity Questionnaire (IPAQ) was used to estimate participants’ level of physical activity during the previous 7 days . The items of the IPAQ are structured to provide a domain-specific score for walking, moderate-intensity, and vigorous-intensity activity. The results are presented as the estimated energy expenditure in metabolic equivalent-minutes per week (MET hours/week). The number of MET hours/week for a specific activity is computed by multiplying the MET value for the activity (3.3 for walking, 4.0 for moderate-intensity activity, and 8.0 for vigorous-intensity activity) by the number of hours spent on that activity .
Stress: The Korean version of the Perceived Stress Scale was applied to assess the degree to which respondents perceived their lives to be unpredictable and uncontrollable over the past month . The PSS consists of 10 items, and higher scores indicate more severe stress. The internal consistency of the questionnaire was confirmed by a Cronbach’s α of 0.88 in this study.
Attitude to eating: Disordered eating in participants was assessed using the Korean version of Eating Attitudes Test-26 (EAT-26) questionnaire. The EAT-26 questionnaire includes 26 items in 4 domains: (i) self-control of eating and bulimic symptom, (ii) preoccupation with being thinner, (iii) food preoccupation, and (iv) dieting [15,16]. Each item is responded to on a 6-point Likert scale, but not all positions on the scale are scored. Each item is given a score of zero for ‘sometimes,’ ‘rarely,’ and ‘never’; a score of 1 for ‘often’; a score of 2 for ‘usually’; and a score of 3 for ‘always.’ The total score ranges from 0 to 78, with higher scores indicating that a respondent is at a higher risk of eating disorders. The internal consistency of the questionnaire was shown by a Cronbach’s α of 0.87 in this study.
Self-efficacy: The Korean adaptation of the General Self-Efficacy Scale was used to measure self-efficacy . It consists of 10 items concerning self-confidence and is measured on 4-point Likert scale. Each question was answered with scores from ‘not at all true’ (1) to ‘exactly true’ (4). The total score ranges from 10 to 40, with higher scores indicating better self-efficacy. The internal consistency of the questionnaire was demonstrated by a Cronbach’s α of 0.89 in this study.
Depression: The Korean version of the Patient Health Questionnaire-9 (PHQ-9) was applied to assess the degree of depression . PHQ-9 is a self-evaluation scale used to measure mental health at primary health care centers . It consists of 9 items assessing the frequency with which patients have experienced depressive thoughts or feelings over the prior two weeks. The severity of depressive disorder is considered mild for scores ranging from 5 to 9 and moderate to severe for score from 10 or more . The internal consistency of the questionnaire was shown by a Cronbach’s α of 0.90 in this study.
General and occupational characteristics: The following general characteristics were analyzed: age, body mass index (BMI), religion, education level, marital status, living with spouse, age at menarche, regularity of the menstrual cycle, length of the menstrual cycle, pregnancy and delivery experience, and history of oral contraception use. BMI classification used for Asian populations . The occupational characteristics were rank, branch, duration of service, working area, duty time, service type, and number of overtime days.
The collected data were statistically processed using the SPSS version 25 (IBM Corp., Armonk, NY, USA). Descriptive statistics were calculated for participants’ characteristics. The differences in HRQOL were analyzed using the independent t-test and analysis of variance. Multiple linear regression analysis was conducted to identify factors significantly associated with HRQOL among military women. A two-tailed probability value of p < 0.05 was considered to indicate statistical significance.