Association analysis of Suboptimal health Status: a cross-sectional study in China

Background Suboptimal health status (SHS) among urban residents is commonplace in China. However, factors influencing SHS have not been thoroughly explored, especially with regard to the effects of internal factors (e.g., personality and health awareness) on SHS. Methods A cross-sectional study was conducted with a nationally representative sample of 5460 Chinese urban residents..SHS was measured using the Suboptimal Health Mesurement Scale Version 1.0. Demographic information, and information pertaining to lifestyle behaviors, environmental factors, and internal factors were abtained through a questionnaire. The associations between demographic information, lifestyle behaviors, environmental factors, internal factors and SHS were assessed using logistic regression. Results Of the 5460 participants (with a mean age of 41.56 ± 16.14 years), 2640 (48.4 %) were men. Out of 36 variables, 23 were significantly associated with SHS: age (odds ratio [OR]: 1.014), an education level of high school/junior college (OR: 1.443) , marital status (OR: 1.899), area of registered permanent residence (OR: 0.767), monthly household income (p < 0.001) , exposure to second-hand smoke (p = 0.001), alcohol drinking (OR: 1.284), bad eating habits (OR: 1.717), not sleeping before 11 p.m. every day (p = 0.002), spending time online more than five hours a day (OR: 1.526), having a good relationship with parents during one’s growth period (OR: 0.602), living with good quality air (OR:0.817), living in not crowded conditions (OR:0.636), having a harmonious neighborhood (OR:0.775), having adequate fitness facilities (OR:0.783), one’s health being affected by two-child policy (OR: 1.468) and medical policies (OR: 1.265) , high adverse quotient (OR: 0.488), many (≥3 kinds) interests and hobbies (OR: 0.617), mature and steady personality traits (OR: 0.469) , a high attention to one’s health (OR: 0.833), and effective health promotion induced by leading a leisurely lifestyle (OR: 0.466) were significantly associated with SHS. Conclusions All these variables were included demographic information, lifestyle behaviors, environmental factors and internal factors. Our study supports the benefits of controlling both internal and external factors in preventing suboptimal health.


INTRODUCTION
Suboptimal health status (SHS) is the ''third state'' between health and disease, carrying the characteristics of transformation from health to disease. According to a 2013 global survey by the World Health Organization (WHO), only 5% of people could be classified as truly healthy, 20% were sick, and people in SHS was accounted in 75% of people (Ma & Zhu, 2013). In addition to acquired immunodeficiency syndrome, hazards that result from SHS have been recognized in the medical field as being of top concern in the 21st century (Zhao, 2006). If SHS is properly handled, the human body can be transformed into a healthy state, or turn the disease the other way around (Chen et al., 2014). It is therefore of significance to explore the factors influencing SHS for its prevention and intervention.Many individuals may not be aware that they are suffering from SHS. For instance, a 1998 study with 6,000 asymptomatic ''healthy people'' indicated that 72.8% of these people were in the ''suboptimal health status'' range (Liu & Li, 2001) . The identification of SHS is the key to preventing the deterioration of an individual's health status. SHS can reportedly be measured objectively using the microbiome (Sun et al., 2020), telomere length (Alzain et al., 2017), plasma stress hormones (Yan et al., 2018), plasma metabolites , glycan (Adua et al., 2019a;Adua et al., 2019b;Wang & Tan, 2019), ideal cardiovascular health metrics (Wang et al., 2017), and traditional Chinese medicine Wang, Russell & Yan, 2014). However, these objective measures are not easily accessible, and may sometimes not be obvious, especially when people feel uncomfortable and are without abnormal symptoms. Self-rated assessment using a questionnaire has been shown to be widely applicable for assessing SHS, with the first Chinese study on suboptimal health measured using a questionnaire being published in the English literature in 2009 (Yan et al., 2009).
With the rapid urbanization in China in recent years, the lifestyle and living environment of urban residents have changed substantially (Chen et al., 2017a;Chen et al., 2017b). However, urbanization is a double-edged sword for urban residents' health (Li et al., 2016). On the one hand, to some extent, urbanization has improved the health benefits of urban residents due to easier access to health care services and knowledge than that available to the rural population. On the other hand, risk factors, such as air pollution, having an unhealthy diet, living a sedentary lifestyle and the life pressure (Miao & Wu, 2016) of chronic diseases were increased for urban residents. The first SHS study that involved urban Chinese population indicated  that SHS was associated with risk factors of chronic diseases and contributed to the development of them. Previous studies have shown that lifestyle behaviors are some of the most important contributing factors including smoking, alcohol consumption, irregular breakfast habits, malnutrition, lack of exercise, and sleeping problems (Lolokote, Hidru & Li, 2017;Chen et al., 2017a;Chen et al., 2017b). Drinking, inadequate breakfast, sleep quality and negative event experience have been reported to be significantly associated with suboptimal health for urban residents (Xie et al., 2016). The environment can also greatly influences one's overall health (Messer, Maxson & Miranda, 2013). As such, SHS can be aggravated by both air pollution (Kelly & Fussell, 2015) and noise (Clark & Paunovic, 2018).
Despite all the above, previous studies on the association factors of SHS for urban residents have only investigated specific aspects, especially external factors, such as lifestyle and environmental factors. Internal factors, such as personality characteristics, and health consciousness have rarely been studied. Materialist dialectics holds that the development of things is the result of both internal and external factors: that the external cause influences the development of things through internal factors. Thus, this study attempts to determine the factors associated with internal factors, such as personality characteristics and health consciousness, and external factors, such as lifestyle and environmental factors, among urban residents in China with suboptimal health.

Study setting and participants
Multi-stage stratified sampling method was used to select participants. For the first stage, according to the administrative regions division and economic development levels in China, one province or city was selected randomly from the following regions: North, Northeast, South-Central, Southwest and Northwest. The selected provinces and cities were Tianjin City, Harbin City, Guangdong Province, Sichuan Province, and Lanzhou City. For the second stage, extracted three to four cities or districts were identified based on the five selected provinces and cities in the first stage while considering their economic level and geographical distributions. For the third stage, one to four districts/streets that were administratively under the identified cities and districts from second stage were selected randomly. For the fourth stage, one to two communities in the selected streets from the third stage were chosen. Qualified participants were then investigated. Sex and age were also considered in the recruitment, under the standard of male: female = 1:1 for sex and Participants had to be more than 14 years old, had lived in the cities or towns for more than half a year, provided verbal informed consent, and voluntarily participated in the survey. The data of those who could not complete the questionnaire due to vision or hearing impairment or other diseases were excluded from the analysis. Urban residents who were ≥14 years old in the identified communities from the third stage were identified as study participants. A total of 7,293 questionnaires were distributed and 6,748 valid questionnaires were collected. Finally, we investigated 1,150, 1,538, 1,898, 1,084 and 1,078 participants in Tianjin City, Haerbin City and Lanzhou city, Guangdong Province and Sichuan Province, respectively The number of participants surveyed in each region met the minimum sample size requirements that was calculated according to the sub-health detection rate in each region (961 in Guangdong Province, 940 in Lanzhou City, 946 in Harbin City, 956 in Sichuan Province, and 928 in Tianjin City).Based on the sampling method and sample size, the overall sample population in this study is broadly representative of urban residents in China. This study was approved by the medical ethics committee of Nanfang Hospital of Southern Medical University (No. NFEC-2019-196). All data collected were kept strictly confidential.

Suboptimal health status
SHS was the health outcome analyzed in this study. This was measured using the Suboptimal Health Measurement Scale version 1.0 (SHMS V1.0) , which had been previously developed by our research group (Sun et al., 2008;Xie et al., 2016;Lu et al., 2013), and has been widely used for SHS assessment and found to be significantly reliable (Xu et al., 2019). The SHMS V1.0 comprises 39 items (SH1-SH39), each including five response, asking the participants to choose the options that are the closest to their actual feelings in the past four weeks. The SHMS V1.0 scale encompasses three sub-scales with respect to physiological suboptimal health (SH1-SH14), psychological suboptimal health (SH16-SH27) and socially suboptimal health (SH29-SH37), whose scores are marked as PS, MS, and SS, respectively. The overall score of the three sub-scales is the score (marked as GS) of the whole scale. Higher scores indicate better health. According to the threshold norm of the SHMS V1.0 scale for urban residents in China (Table 1) established according to gender and age in our previous study (Xu et al., 2019), the health status for Chinese urban residents can be divided into three states with respect to disease, SHS (including severe, moderate, and mild SHS) and health.

Covariates
A total of 36 variables were investigated for the association analysis, with the pertinent data elicited from participants using a self-completed questionnaire. All variables were summed up into four parts: demographic information, lifestyle behaviors, environmental factors, and internal factors.
Demographic information included the participants' registered permanent residence, which was categorized as either urban or rural; educational level, which was categorized as either junior school and below, high school/junior college, or university and above; marital status, which was categorized as either married, unmarried, divorced, or widowed; and monthly household income per capita ( ), which was categorized as either < 2,500, 2,500-5,000, 5,000-7,500, 7,500-10,000, or above 10,000. Lifestyle behaviors include smoking status, which was categorized as either nonsmoker, past smoker (smoked in the past and quit a month ago), or smoker; exposure to secondhand smoke, which was categorized as never, occasionally, sometimes, or often; alcohol drinking, which was categorized as either yes or no; breakfast habit, which was defined as the frequency of having breakfast, which was categorized as either every day, often, sometimes, occasionally, or never; bad eating habits, which included irregular eating, poor dieting, overeating, partial or picky eating, high intake of salt, eating spicy food, and often eating snacks instead of regular meals, which were categorized as either yes or no; falling asleep before 11 p.m., which was categorized as either every day, often (3-6 days/week), or rarely (≤2 days/week); spending time online, which was categorized as either <1 h, 1 h, 3 h, or ≥5 h; basking in the sun, which was categorized as either ≥7 h, 3 h, 1 h, or <1 h; and physical exercise, which was categorized as either every day, often (5-6 days/week), sometimes (3-4 days/week), or occasionally (<2 days/week). Meanwhile, environmental factors include the relationship with parents during one's growth period, which was categorized as either good or bad; living with good quality air quality, living with plentiful greenery; living in simple or crude houses, living in crowded conditions, living in a harmonious neighborhood having access to adequate fitness facilities; having access to adequate medical and educational resources; living together with family; one's health affected by medicine policies and one's health being affected by the twochild policy, which were all categorized as either yes or no; family structure, which was categorized as either incomplete, nuclear, or extended family; and parents' discipline, which was categorized as either spoiled, stern, or positive.
Finally, internal factors included adverse quotient, which was categorized as either low or high; interests and hobbies, which were categorized as either few (<3) or many (≥3); personality traits, which were categorized as either anxiety and irritability, swallowing rage and suffering in silence, impatient and aggressive, or mature and steady; attending health training and lectures, which was categorized as either occasionally, sometimes, or often; health promotion exerted by leading a leisurely lifestyle, which was categorized into moderate or mild, or good; life attitude, which was categorized as either negative or positive; being ware of the importance of interpersonal communication, which was categorized as either unimportant, general, or important and attention to one's own health, which was categorized as either low or high.

Statistical analysis
The software SPSS20.0, R and AMOS23 were used for the statistical analysis. Using percentage for the descriptions of count data, we conducted a comparison using chi-square test. Quantitative data were described as (X ± S) and analyzed using t -test. A generalized linear mixed model (GLMM) was used to calculate the intra-class correlation coefficient (ICC) and examine the cluster effect of the sampling area. Logistic regression was used to analyze the influencing factors, which turned out to have statistically significant difference (p < 0.05).

RESULTS
The SHS incidence rate of urban residents in the five investigated provinces and cities in China was 66.7%. The average age of these urban residents was 41.56 ±16.14, of which 2640 (48.4%) were men and 2820 (51.6%) were women. The descriptive analysis and comparison by gender are presented in Table 2. Females were more likely to be divorced and widowed, have a monthly household income per capita less than 5000/month, have a higher body mass index, be a nonsmoker, have never exposed to secondhand smoke, not drink alcohol, have breakfast every day, bask in the sun less than three hours a week, occasionally do physical exercise, fall asleep before 11 p.m. (day/week) every day, live together with family, have parents who practiced disciplining, live with plentiful greenery, live in a harmonious neighborhood, have access to adequate fitness facilities, have access to adequate medical and educational resources, have a positive life attitude, have a low adverse quotient, have few interests and hobbies, have a swallowing rage and suffering in silence and anxious and irritable personality, and often attend health training and lectures.

Association analysis
The analysis of GLMM model revealed that ICC of the sampling area was 0.019 (95% confidence interval (CI) [−0.018-0.057], p = 0.228), revealing that there was no cluster effect on the sampling area. Thus, the association analysis of demographic information, lifestyle behaviors, environmental factors, and internal factors with SHS could be carried out using logistic regression.
Following the logistic regression analysis, of the 37 investigated covariates, 23 variables were found to be associated with SHS (Table 3)

DISCUSSION
This study was the first to systematically investigate the influencing factors of SHS from the aspects of demographic information, lifestyle behaviors, environmental factors and internal factors with a sample of Chinese urban residents at the national level. A total of 23 variables were significantly associated with SHS, of which 12 were significantly associated with males and 14 with females. All these variables that were significantly associated with SHS were from demographic information, lifestyle behaviors, environmental factors and internal factors, which thereby indicates that the association factors were widespread, not only demographic information and external factors, such as lifestyle behaviors and environmental factors, but also internal factors. Regarding demographic information, age was significantly associated with SHS in all participants. However, association with SHS was not found between men or women. For all urban participants, especially males, whose registered permanent residence was in an urban area, it was found that there people were not easily prone to suboptimal health. This finding was in line with the actual real-life situation in society that rural-urban migrant workers have greater life stress and work stress than do urban-native residents (Cui et al., 2012). Education level was found to be significantly associated with SHS in all participants, especially in males, with having a higher education level leading to an easier chance of developing SHS. This might be due to high-pressure jobs and working longer hours than people with lower educational levels (Schieman & Glavin, 2011). Women who ate divorced and widowed have been reported to have a 82.5% higher risk of developing SHS compared with married women. Compared with men, divorced women have an increased risk of living in poverty and being a single parent (Leopold, 2018); being widowed may severely restrict women's ability to access financial, affective, informational, or physical resources, which in turn may affect health outcomes (Perkins et al., 2016). Previous studies have reported a significant association between income and health. Studies in the United States have pointed out that the effect of income on health tapers off at around the median level of income (Knaul et al., 2006;Arsenijevic, Pavlova & Groot, 2013). Our findings are in line with these studies in the United States. We also found that women whose monthly household income per capita was between 5,000 and 7,500 were not prone to developing SHS compared with those whose income was less than 2,500.
Concerning lifestyle behaviors: The impacts on health exerted by secondhand smoke are self-evident (Iloh, 2017). In the present study we investigated the same association of exposure to secondhand smoke with suboptimal health in males. The risk of detection rate of suboptimal health was increased when exposure to secondhand smoke was more severe. Alcohol drinking also plays a significant role in the etiology of many acute  and chronic diseases, and can cause a major burden to the population's health ,accounting for 4% of disability adjusted life years worldwide (Whiteford et al., 2013). Alcohol consumption can increase the risk of SHS by 37.4% in females. However, no significant association was found between alcohol consumption and SHS in men. This difference between males and females may be explained by the cause for drinking. Drinking in Chinese culture can be classified mainly as social drinking, which is an actively usually widely accepted in men than women (Cochrane, 2003). In our study, we found that bad eating habits were associated with SHS in both males and in females. These bad eating habits that were investigated included irregular eating, poor dieting, overeating, partial or picky eating, high intake of salt, eating spicy food, and usually eating snacks instead of regular meals and etc. Eating salty food is not good for the health and may increase the risk of incidence of stomach cancer (Park et al., 2016). While having an unhealthy diet or overeating can induce heavy gastrointestinal burden and go against one's overall health (Janssen, 2010). Meanwhile, spending a prolonged amount of time online may cause backache, neck, finger, wrist, and arm pain, as well as emotional fluctuation, tension and anxiety, fatigue and other SHS symptoms (Karacic & Oreskovic, 2017). In traditional medicine, the time past 11 p.m. is considered to be the time for organ detoxification, and a need for deep sleeping (Li & Li, 2017). Going to bed before 11 p.m. and having enough hours of sleep are important for the strengthening of the body's resistance and immunity (Chen, 2012). We investigated whether there is a significant association with falling asleep before 11 p.m. and SHS, and for those who can't could not fall asleep before 11 p.m. whether these people had a higher risk of developing SHS. We found that spending time more than five hours a day online increased the risk of SHS by 66.8%.
As to environmental factors, males and females with good relationships with their parents during their growth period were less susceptible to SHS, which is consistent with the findings of several previous studies (Xue et al., 2019a;Xue et al., 2019b;Xue et al., 2019c). More attention should be paid to the relationship between parents and children when proceeding with family education to allow for the protections of children's health and growth. Good air quality is closely associated with optimal health, and the present study showed that women who live with good air have a lower risk of attaining suboptimal healthy. However, this association was not found in males. Living in crowded conditions showed negative association with SHS in males, but not in females. This might be because living in crowded conditions comes with foul air, disturbing noise, and tension, which impose strains and harm to people's physical and mental health (Gibson et al., 2011). We found that living in a harmonious neighborhood and having access to adequate fitness facilities were all associated with SHS in females, not in males. Harmonious neighborhoods brings with them a safe and mutually supportive living environment, which is good for both physical and mental health. A study has shown that higher perceived neighborhood disorder was significantly associated with a higher level of total health service usage among those with lifestyle illnesses (Martin-Storey et al., 2012). The popularization of community fitness facilities has provided residents with convenience in accessing and undertaking fitness programs and helps to ease residents to participate in fitness programs, especially for those with weak fitness awareness; the popularization of such facilities is an important component of the Healthy China 2030 plan (Li, 2018). Both male and female patients whose health was affected by the two-child policy had higher risk of developing SHS. A major concern after the implementation of two-child policy has been the acute shortage of pediatricians and paediatric nurses in China, which has worsened over the past decade (Han, Hu & Wang, 2014). Therefore, for parents with lower incomes and who work in high-pressure working conditions, the demand for a newborn child will inevitably bring more anxiety which is not good for the health (Ren et al., 2015).
Lastly, on internal factors, adverse quotient,( also known as setback business or counter business), refers to people's ability to resolve and withstand setbacks, usually the more one is able to bear such setbacks, the higher the adverse quotient is (Zhao, 2016). In our research team's previous study, it was found that the higher the adverse quotient, the lower the risk of suboptimal health (Xue et al., 2019a;Xue et al., 2019b;Xue et al., 2019c). In the present study, we found that a high adverse quotient was a protective factor against SHS in both males and females. Participants (both males and females) with more than three kinds of interests and hobbies had a lower risk of developing SHS compared with those with less than three interests and hobbies. People with a wide range of hobbies have been reported to be less likely to have mental health problems, and their physical to be better than those with less interests and hobbies (Hirosaki et al., 2009). Furthermore, the findings of our group's previous research indicated that the personality and SHS were related, and that those urban residents with a personality pertaining to swallowing rage and suffer in silence, inpatience and aggressiveness have significantly lower scores than those of urban residents with a mature and steady character (Xue et al., 2019a;Xue et al., 2019b;Xue et al., 2019c). Hence, the development of a mature and steady personality may have a positive effect for improving health. This study also exhibited the same findings in both males and females.
The protective effect of high attention to one's health with SHS was found in all participants, not between females nor in males. The protective effect of effective health promotion induced by leading a leisurely lifestyle with SHS was found in both males and females. The forms of leisure and its corresponding effects are of great significance for fatigue reduction and health recovery (Kubo et al., 2013). Proper recreational activities were contributed to health promotion, and enhance the quality of life and health outcomes.

Limitations
This study has several limitations. First, although we used face-to-face interviews, all data were collected from a respondent-completed questionnaire; thus, responses may have a level of inherent inaccuracy or bias. Second, although we used a four-stage stratified sampling method, sampling errors were still inevitable. Lastly, this study can only find correlation, not causal relationship, due to its cross-sectional study rather than longitudinal approach.

CONCLUSIONS
Through this large cross-sectional study of Chinese urban residents, we found that SHS was significantly associated with demographic information, lifestyle behaviors, environmental factors and internal factors, both in males and females. Our study supports propositions regarding the benefits of controlling both internal and external factors in preventing suboptimal health.