Relationships between ideal gure, lifestyle habits, physical activity and self-rated health in Japanese female healthcare students

Self-rated health (SRH), a subjective perception of an individual’s overall health, is widely used in public health. The transition from adolescence to young adulthood is a critical period, with signicant changes in lifestyle and dietary habits. It is therefore important to understand the self-rated health of young Japanese women. The aim of this study to provide basic data on the epidemiological features of SRH in female students of healthcare subjects, including their recognition of appropriate physique, lifestyle habits, and levels of physical activity. A cross-sectional survey was conducted in a total of 1101 female in Body mass index was calculated from body height and using data from health examinations, and and were using several previously-validated Multivariate logistic regression analysis was used to investigate the relationship between self-rated and for lifestyle and physical activity, adjusting for grade and smoking.


Results
The odds ratio of poor/fair self-rated health was 1.87 (95% con dence interval (Cl) 1.13-3.24) for lower vs higher levels of activity, 5.38 (3.59-8.10) for those with vs. without insomnia, and 0.44 (0.28-0.69) for the group who wanted to be thin, rather than those whose ideal weight was standard.

Conclusions
Young women tend to want to be thin, so it is important to provide health education that will help them to understand appropriate weight on a medical basis, and prevent health problems caused by the inappropriate idealization of thinness. Background Self-rated health (SRH), a subjective perception of an individual's overall health, is a measure widely used in public health discipline. Typically, SRH is examined using a single question, i.e., asking respondents to rate their overall health on a scale from excellent to poor [1]. According to Kaplan, persons with better SRH have higher survival rates than do those with poorer SRH, regardless of the presence or absence of disease [2]. Additionally, SRH affects life expectancy, an index that is highly predictive of mortality risk [2].
Furthermore, the validity of SRH measures to predict mortality risk has already been established in multiple studies [3]. Study results indicate that SRH is affected by several lifestyle, diet, and biochemical factors [4,5].
The SRH of Japan's general population is assessed o cially every 3 years via the Comprehensive Survey of Living Conditions (CSLC), a nationwide cross-sectional survey of a representative sample of the country's general population. The CSLC from 2016 found that 86.7% of men and 84.4% of women had excellent, very good, or good SRH [6]. SRH assessment among adolescents is an effective way to evaluate their self-concepts of health [7,8]. A high SRH in adolescents has been found to be strongly associated with general well-being and psychosomatic symptoms [9,10]. In Japan, studies have examined whether the younger generation's knowledge affects their health behaviors or SRH. For example, one study examined whether female university students' accurate knowledge about the healthiness of foods contributed to desirable eating behaviors [11]. Another study examined male university students' smoking knowledge and practices [12].
It has been con rmed that there is a correlation between awareness of bad lifestyle habits and smoking behaviors, healthy eating habits, and personality traits (e.g., feeling inferior).
The transition from adolescence to young adulthood is a critical period during which an individuals' preexisting habits may be disrupted [13]. Leaving home and the education system at this age are associated with negative diet changes [14], which can have signi cant and long-lasting effects on the future health of individuals and their families [15,16].
The annual National Health and Nutrition Survey conducted by the Ministry of Health, Labour and Welfare suggests that young women in Japan tend to be thin. The 2016 survey found that the number of women who were "thinner (low body weight)" with a body mass index (BMI) of less than 18.5 has signi cantly increased compared to 10 years before, with 20.7% of women in their 20 s falling into this category. Being thin is associated with several health problems in young women, and malnutrition among young women and pregnant women may also increase the risk of lifestyle diseases in their children [17][18][19][20]. Therefore, it is important to examine and understand the SRH of young Japanese women.
This study sought to provide basic data on the epidemiological features of SRH in female students, including their recognition of and knowledge about healthcare subjects such as appropriate physique, lifestyle habits, and physical activity levels.

Methods
A cross-sectional study was conducted among 1305 female students who participated in a periodic health examination between April and May 2018 at a Japanese medical university. The students were from nine departments: radiological technology, clinical nutrition, physiotherapy, medical welfare, acupuncture, clinical engineering, medical information science, pharmaceutical sciences, and nursing. All participants provided written informed consent before participating in this study and understood that there was no penalty for choosing not to participate. The paper-based questionnaire was distributed only to students who had given written consent. Students who received the questionnaire completed it during their physical examination.
Body height and weight data was obtained from the periodic health examination. BMI was calculated as weight in kg/height in m2. Global SRH measures generally include a question asking "How would you rate your overall health?" with ve response categories ranging from excellent to poor (i.e., excellent, very good, good, fair, and poor). These ve categories are dichotomized into either good health (excellent, very good, or good) or poor/fair health (fair or poor) [21][22][23].
The seven independent variables for this study were grade (1-2 or ≥ 3), living status (living with others or living alone), smoking (none, past smoker, or current smoker), alcohol drinking (none, a few times per month, a few times per week, or daily), University of California Los Angeles (UCLA) activity score (< 5 points or ≥ 5 points) [24], Athens Insomnia Scale (AIS; non-insomnia or insomnia) [25,26,27], and frequency of breakfast consumption (< 6 days/week or ≥ 6 days/week).
Using Noh et al.'s method [28], we classi ed the participants into three groups by desired weight (underweight, overweight, or normal weight), as measured by the relationship between their current BMI and their desire to lose or gain weight. Physical activity was assessed using UCLA activity score [24], which we have used in previous research [29].
AIS is a self-assessment insomnia scale created by the World Health Organization for the World Project on Sleep and Health. This instrument's reliability and validity have already been veri ed in other studies [25,26,27]. AIS items measure waking during the night, early morning awakening, total sleep duration, sleep quality, and daytime sleepiness. Each of the scale's eight questions is answered from 0 (no problem) to 3 (a very serious problem). A total score of 4 or more on the selected items shows a suspicion of insomnia, and a total score 6 or more indicates insomnia.
We asked participants "Do you want to gain or lose weight in the future?" and de ned their perceptions of their ideal weight into the three groups: underweight, overweight, and standard weight. If current BMI was < 18.5, but they wished to lose weight or stay the same, participants were de ned as wanting to be underweight. Those with a current BMI < 18.5 who wanted to gain weight were de ned as wanting to be on standard weight. Those with a current BMI of ≥ 25.0 who wanted to gain weight or stay the same weight were de ned as wanting to be overweight, and if they wished to lose weight, they were de ned as wanting to be on standard weight. If current BMI was 18.5-24.9, those who wanted to lose weight were in the wanting to be underweight group, those who thought they needed to gain weight were in the wanting to be overweight group, and those who wished to stay the same weight were in the wanting to be a standard weight group (Fig. 1).
Participants were classi ed as having either good SRH (excellent, very good, or good) or poor/fair SRH (fair or poor). Independent variables were compared between groups. Differences in categorical variables between those with good and poor/fair SRH were evaluated using the chi-square test.
Multivariate logistic regression analysis was used to examine the relationship between dietary habits, lifestyle, physical activity, recognition of physique, and SRH, after adjusting for grade and smoking. The independent variables included UCLA activity score, AIS scores, frequency of breakfast consumption, and recognition of physique. Adjusted odds ratios and 95% con dence intervals were calculated. All statistical analyses used JMP 9.0.2 (SAS Institute Inc., Cary, NC, USA).

Results
In total, 1305 women students participated in the periodic health examinations, of which 1101 completed the questionnaire, accumulating a response rate of 84.4%. The mean participant age was 19.7 years (standard deviation [SD] = 2.7; range = 18-46 years), and the mean BMI was 20.9 (SD = 3.0; range = 14.3-38.4). Table 1 shows the responses to the question "Do you want to gain or lose weight in the future?" based on current BMI data which were classi ed as recognition of physique. Many students with a BMI < 18.5 or 18.5-24.9 wanted to lose weight. Participants' grades, lifestyle habits, dietary habits, physical activity levels, recognition of physique, and SRH are shown in Table 2. The largest group under recognition of physique was those who wished to be underweight.   Table 3 shows the bivariate analysis of the independent variables with SRH. Grade and smoking were associated with SRH. However, because living status and alcohol drinking had no association with SRH, these two variables were not included in the logistic regression analysis. Table 4 shows the results of the logistic regression analysis of factors associated with poor/fair SRH in all participants. While UCLA activity score (≥ 5 points) and AIS (insomnia group) were positively correlated with poor/fair SRH, there was a negative correlation with the wanting to be underweight group.

Discussion
This study has examined the relationships between the SRH of women students at a Japanese medical university and their demographic characteristics, lifestyle habits, dietary habits, and physical activity levels. Results indicated that UCLA activity score, AIS, and recognition of physique were signi cantly associated with poor/fair SRH. Overall, this cross-sectional observational study of lifestyle habits, dietary habits, and physical activity in women students revealed that lower physical activity and insomnia were signi cantly positively associated with poor/fair SRH. However, wanting to be underweight was signi cantly negatively associated with poor/fair SRH.
Insomnia has been identi ed as the most common sleep disorder [30]. Various insomnia risk factors have been identi ed in the general population, including being female and being obese, both of which increase the risk for chronic insomnia [31]. In this sample of female university students, we found low levels of obesity but high levels of insomnia. A cross-sectional study of students from seven universities in Poland found a strong positive correlation between insomnia levels and stress levels [32]. Another study in Japan validated the simpli ed Japanese version of the AIS (AIS-SJ) in relation to psychological problems [33]. Therefore, the students in our study may have had poor/fair SRH because of stress or psychological problems.
SRH was positively associated with physical activity, as shown in this study. This result is consistent with other ndings about the relationship between physical activity and SRH in young adults [34,35]. Several possible hypotheses could explain the relationship between physical activity and health, including physiological [36] and psychological hypotheses [37]. However, because females tend to judge their SRH as good or bad based on various factors (e.g., pain and mental/physical symptoms [38]), these ndings likely re ect several combinations of factors. Whatever the precise reason, there is an independent association between a lower physical activity level and poor SRH, which is why public health programs encourage regular physical activity.
Most of the study participants were either normal weight or underweight, with very few overweight. Regardless, the majority of students wanted to be thinner. Interestingly, the group who wanted to be underweight still considered itself to be healthy. Baba et al. reported that wanting to be thinner was positively correlated with a sense of gain or loss about one's body, being praised, and sex role acceptance, but it is negatively correlated with self-esteem and feelings of stress [39]. These psychological factors might affect the desire to be thin, as individuals may feel a sense of merit in losing weight. These studies, including the current study, suggest that many young women misinterpret appropriate body weight and have developed an erroneous body image and view of SRH. One study among Japanese young women [40] reported that groups of underweight women-both those with and without a desire to be thinnerrequired nutritional education to help them maintain an appropriate body weight. Because the young women in our study had a strong desire to be thin, providing health education designed to help them achieve recognition of an appropriate, science-based body weight will be an important strategy to prevent health problems caused by the inappropriate recognition of physique. We suggest, therefore, that any education designed to help young women understand and correctly rate their own health should include a psychological approach along with nutritional and health education.
This study had some limitations. First, it was conducted in a medical university and, therefore, was not population based. These participants may have had healthier lifestyles and been more health-conscious than the general population of the same age. Caution should therefore be exercised when generalizing these results to the general population, even among those in the same age group. Moreover, while the study's convenience sampling may have contributed to selection bias, the students still showed high levels of incorrect recognition of physique, suggesting that the results are likely to be valid. Next, this study employed the recognition of physique measure used by Noh et al. [28], but the validity of this approach has not been examined. Finally, because this study was cross-sectional, causal relationships could not be determined. In the future, we need to examine whether physical activity, sleeping, and recognition of physique are the results or causes of SRH.

Conclusion
We conducted a cross-sectional study to investigate the relationship between SRH and BMI, lifestyle habits, and recognition of physique among women students at a medical university. We found that UCLA activity score, AIS, and recognition of physique were all signi cantly associated with poor/fair SRH. We suggest that health education that includes information about physical activity and sleeping is important for improving SRH among women students at this university. Additionally, to prevent health problems caused by the inappropriate recognition of physique, it is important to provide health education to enable young women to develop an appropriate recognition of the ideal physique that is grounded in science.
Abbreviations SRH: self-rated health, CSLC: the Comprehensive Survey of Living Conditions, BMI: body mass index; UCLA: University of California Los Angeles; AIS: Athens Insomnia Scale.

Declarations
Ethics approval and consent to participate All participants provided written informed consent prior to participating in the study, which was approved by the Institutional Review Board of Suzuka University of Medical Science (approval no. 356). This study was conducted in accordance with the principles of the Declaration of Helsinki.

Consent for publication
Not applicable.

Competing interests
The authors declare that they have no competing interests.

Funding
This research did not receive any speci c grant from funding agencies in the public, commercial, or notfor-pro t sectors.
Authors' contributions MO, YW, TN, SU and TO designed the study. MO, YW and TN conducted the experimental work. MO, SU and TO analyzed the data, prepared the gure, and drafted the manuscript. All authors participated in data interpretation and revised the manuscript. The nal version of manuscript was approved by all authors.