Our results showed that sub-health residents in Zhuhai accounted for 56.8%. This figure was slightly lower than that in a study conducted by Sun et al. on sub-health residents in Guangdong Province [17]. This may result from the differences in their samples and questionnaires [18-20]. Our study found that the proportion of participants with sub-health status varied across different age groups. Previous studies indicated that middle-aged people were more likely to experience sub-health status since they were at a critical stage of their career (e.g. personal promotion) and personal life. They had to face up with a lot of problems relating to their interpersonal relationships, children’s education, economic pressure, and responsibility for taking care of elderly family members. All these might increase their exposure to physical and mental problems [21, 22]. In our study, the 25-34-year-olds constituted the highest proportion of all participants having sub-health conditions (27.4%). This means that the sub-health population tends to be younger, and therefore, more attention should be paid to them. In addition, better-educated participants were less likely to be vulnerable to sub-health. A possible explanation is that they had better healthcare-related knowledge, more effective psychological adjustment methods, and healthier lifestyles [23].
Sub-health status assessed by the SHMS V1.0
The PS score of the sub-health group was the lowest of all the three sub-scales. This indicated that physical sub-health was the key factor leading to sub-health status. The symptoms of physical sub-health include lack of energy, insomnia, bitter taste, headache, as well as pain in body parts, like waist and legs. This causes an individual more susceptible to diseases. In view of this situation, boosting the immunity system is the best way to defend against harmful infections and diseases, and promote good health [24, 25]. To have a better immune system, a person needs to pursue a healthy lifestyle that balances different aspects of life, including work, rest and physical activity, have a balanced diet, and consume recommended dietary supplements.
Determinants of sub-health
The multivariate regression model showed that the pace of residence had the greatest impact (OR=1.60) on sub-health status. Urban residents were more likely to be in a sub-health status. Since the economic reform in 1978, Chinese economy has been growing at a rapid pace, leading to greater urbanization. Environmental pollution derived from urban development, pressure relating to resource allocation, and social competition have posed a lot of health threats to urban residents [26].
Social support is the external support, whether material or spiritual, that an individual receives when facing a stressful event. In our study, individuals having no close neighbors, relatives and friends in the SS were at a higher risk of sub-health status (Many vs. None, OR=1.31). As an intermediary factor between stress and physical health, social support plays an important role in protecting an individual’s physical and mental health. Most scholars believed that unlike negative social relations, positive social support is beneficial to physical and mental health [27, 28]. Therefore, lack of social support is considered to be an important contributor to long-term fatigue existence of sub-health and dysfunction. Lower social support puts a person at a higher risk of having sub-health conditions. Our results also showed that the score of social resource and support in the sub-health group was lower than that in the non-sub-health group.
Emotion plays a crucial part in the occurrence and development of sub-health status. Happy feelings (Always vs. None, OR=1.29) and negative emotions or depression (None vs. Always, OR=1.28) in the MS were deemed as two other important factors leading to sub-health status. With the acceleration of modern social life, negative emotions usually include depression and stress. They may further develop into anxiety disorders and non-communicable diseases, seriously threatening human health unless timely interventions are implemented [29]. Psychological adjustment is an irreplaceable approach to solving sub-health problems through improving self-cultivation, establishing a positive outlook on life, and taking courage to face reality [30].
Other contributors to sub-health status included the frequency of physical exercise per week (Daily vs. None), appetite (Very good vs. Very poor), gastrointestinal upset (None vs. Always), walking 3-5 stairs (None vs. Very difficult), memory (Very good vs. Very poor), and interpersonal relationship (Very satisfied vs. Very unsatisfied).
Limitations of the study
Our study encountered two potential limitations. Firstly, as a cross-sectional study, it can result in the information bias of measuring the study outcome. Secondly, we only surveyed the participants in Zhuhai city on account of time and resource restrictions; hence, these findings may not be generalizable to other regions in Guangdong province. Further studies, therefore, need to be conducted with more statistical methods while taking our limitations into consideration.