The survey showed that the detected prevalence of sub-health status among college students was 64.4%, which was similar to the results of many related studies in China [6–11] The figure was lower than the detected SHS prevalence of 75% in the WHO report , which may be explained by the fact that college students are in their young age, with good physical conditions and strong health awareness. However, the detected prevalence of sub-health was still fairly high among college students, which might be related to the social life stress incidents in this major outbreak.
SHS primarily manifests as changes in the physiological, psychological, and social dimensions . Given the rapid outbreak, strong infectiousness, and severe symptoms, special medicine against the virus still remains unavailable. This situation is likely to induce public anxiety and panic and easily affect the physical and mental health of college students to varying degrees. The results of this study showed that the physiological SHS was the best, followed by the psychological SHS, suggesting that the college students were generally in good physical conditions during the pandemic. A study  showed that college students staying home exhibited various levels of emotional problems during the pandemic. For example, bored and upset students accounted for 72.87%, and anxious and worried ones accounted for 65.69%. The postponed semester of colleges and universities, the unscheduled date of school reopening, and the stress of academics and career during the graduation season all have varying degrees of impacts on the mental health of college students. In addition, with relatively higher education levels, college students tend to be quick to acquire and grasp information. A survey  showed that 73.3% of college students frequently or always checked on the updates about COVID-19. Excessive attention paid to the pandemic may also induce the occurrence of psychological SHS. The results of this study showed that social SHS was the worst among the three subscales. This might be related to the college students’ boredom of learning at home, lack of learning atmosphere, inadequate self-discipline, and difficulty with adapting to a new learning mode. The discomfort caused by staying indoors too long, tedious environment and routines, and changes in lifestyle may also be relevant. Further analysis of the questionnaire items showed that college students had the lowest scores in seeking help actively, keeping in touch with friends, and receiving material or emotional support from classmates and families. This may be explained by the fact that college students usually live in the campus and spend less time at home, and now they have to get along with their family members all day long during the pandemic but only to find that they share few common topics. Moreover, college students may have a strong ego perception and are not good at interacting with others , and they tend to communicate with the outside world less while staying home.
The above is the current status of SHS of college students during the COVID-19 epidemic. At the same time, this study shows that there are differences in SHS of college students with different characteristics during the COVID-19 epidemic.
Being the only child was the protective factor for SHS scores of college students during the COVID-19 pandemic (P < 0.05), as only children had better SHS scores than non-only children. Contrary to the results of Lian Guixiong et al.  ,who believed that only children generally had worse sub-health symptoms than non-only children, this might be related to the particularity in the pandemic period of COVID-19. Some studies [17–19] showed that only children had higher levels of psychological health than non-only children, which was consistent with the results of this study. This might be explained by the fact that only children normally have a small family size, which is more financially affluent. When staying home, they can receive sufficient attention from families, fully satisfied both spiritually and materially. As a result, their enhanced sense of well-being would be unlikely to induce panic or helplessness. In addition, only children may be more proactive in interacting with people  and more willing to talk to others during the pandemic.
Spending more time on electronic devices was the risk factors for SHS scores of college students during the COVID-19 pandemic (P < 0.05). The less usage of electronic devices, the higher the SHS scores, and the closer to health status. According to the Proposed Diagnostic Criteria for Internet Addiction published by Tao Ran et al. , the Internet addiction was diagnosed by daily internet use for at least six hours per day, lasting for at least 3 months. In this survey, college students who spent no less than six hours on electronic devices accounted for 61.6%. The underlying reason might be that the tedious daily routine heavily relied on spending time on the Internet, such as playing games, watching series, or browsing news Meanwhile, online learning at home should also be taken into consideration, as they would need to use their computers to watch videos, search papers, or use their smart phones or tablets to read course martials and learn vocabulary. The impact of extended use of electronic devices on health should not be underestimated. Multiple studies have shown that extended use of electronic devices can have harmful effects on the physical health of college students [22–24], causing headache, neck and shoulder discomfort, visual fatigue, and dry eyes. Studies have also shown that prolonged exposure to the screens of electronic devices can reduce cognitive and sensory capabilities . Properly controlled use of electronic devices would be conducive to lowering the occurrence of SHS. When scheduling online courses, schools should be careful to balance between study and rest. As far as college students are concerned, the top priority is to improve self-discipline, especially in using electronic devices. In addition, they should make good plans of daily life and learning with activities such as practicing brush writing, learning embroidery, or painting, which can effectively regulate boredom and irritability.
Sleeping after 11 PM more often and sleeping fewer hours per night were the risk factors for SHS scores during the COVID-19 pandemic (P < 0.05), which was consistent with the findings of Xi Junyan et al . Students who slept before 11 PM had better SHS, but they only accounted for 12.4%. In other words, 87.6% of college students kept staying up late during the pandemic. College students who slept less than eight hours per night had the lowest SHS scores, that is, the worst SHS, accounting for 23.9%. Students who slept eight to ten hours had the highest SHS scores, that is, the best SHS, accounting for 62.5%. In this regard, most students had enough sleep, possibly because they had more rest time due to the postponement of school reopening. In 2015, the National Sleep Foundation (NSF) issued its recommendations for appropriate sleep recommendations. It recommends sleep range of 7 to 9 hours per night for younger adults (18 to 25). The optimal time to fall asleep is before 10 PM and no later than 11 PM. Poor sleep quality directly affects the efficiency and safety of people’s daily behaviors, as well as the physical and mental health. It may result in decreased immunity, depression, and even a variety of diseases . The analysis of questionnaire items showed that college students tended to have poorer sleep quality, partly because they became less motivated for studying at home, concerned about their progress, and worried about the public health emergency. Good sleep quality promotes physical and mental health and improves learning efficiency . Schools can take the following measures: 1. Make plans of daily routine and study programs for the students’ reference, guiding them to develop good discipline. 2. Maintain contact and communication with students, track their learning progress at home, and pay attention to students’ physical and mental health, so as to provide psychological guidance in a timely manner. 3. Use the school’s online platform to inform students of the true news about the pandemic in real time, and share scientific tips to guide them to actively and effectively deal with the situation. In the other hand, the college students can improve their sleep quality by incorporating appropriate exercise and balancing diet, so as to prevent the occurrence of SHS.
Exercising fewer times per week and exercising for fewer minutes each time were the risk factors for SHS scores during the COVID-19 pandemic (P < 0.05). Those took more times of exercise per week had higher SHS scores. Those who exercised more than three times per week had the highest scores and were closer to being healthy. For different durations of exercise each time, 34.2% of college students exercised for 30 minutes to one hour, and they had the highest SHS scores and were closer to being healthy. This was consistent with Liu Jie , who suggested that college students should exercise for 20 to 45 minutes each time, three times or more each weak. In this survey, students who exercised more than three times per week accounted for 14.7%, while those exercising one or two times accounted for 44.8%. In other words, the majority of students still kept exercising while at home. Proper exercise can not only promote blood circulation, eliminate fatigue, improve cardiorespiratory capacity, but also cultivate one's moral character, hone the power of will, and enhance self-confidence. A study  has shown that moderate exercise on a regular basis can significantly increase saliva IgA concerns and secretion rate, reduce the risk of upper respiratory tract infections, and enhance the body’s immune function. Therefore, in the outbreak of the highly infectious 2019-nCoV, it is particularly necessary to strengthen prevention by improving physical conditions. During the pandemic, college students can enrich their daily routine through yoga, aerobics, and Tai Chi.
Skipping breakfast and eating irregular meals were the risk factors for SHS among college students during the COVID-19 pandemic (P < 0.05). Those eating breakfast and regular meals had higher scores and were closer to being healthy. In this study, 31.9% of college students never or occasionally ate breakfast, which could easily lead to SHS. In the other hand, 69.8% of college students always had regular meals and developed good eating habits. As the most important meal of the day, breakfast should account for 30% of the total food intake throughout the day . Often skipping breakfast can easily result in low blood sugar, which seriously affects the efficiency of learning, while increasing the risks of diseases such as gastrointestinal diseases and gallstones. Regular diet is conducive to physical supplementation, provides various nutrients required by the body, and maintains the functional vital activities. Analysis of the questionnaire items showed that college students tended to have poorer appetite during the pandemic. The underlying reason might be the reduced activity and consumption when staying home. It may also be related to mental stress. College students should apply the following measures: 1. Improve their appetite and relieve stress by cooking at home. 2. Increase the amount of activities and promote appetite by doing housework or working as a community volunteer.