## 1 Introduction  
In recent years, with the acceleration of urbanization and industrialization, China's economy has developed rapidly, and the living standards of Chinese residents have further improved. According to the data released by the National Bureau of Statistics, in 2021, the per capita disposable income of Chinese residents was 35,128 Renminbi (RMB), representing a year-on-year increase of 8.1%. Moreover, the per capita consumption expenditure was RMB 24,100, representing a year-on-year increase of 12.6%, of which per capita healthcare expenditure accounted for 8.8% [1]. On the one hand, it can be seen that, while material needs are constantly being satisfied, people begin to pay more attention to their own health problems, and people are eager to obtain more convenient and efficient online medical services [2]. On the other hand, China's medical security system is facing a series of challenges, including the following: (1) A high rate of population aging--by 2020, China's elderly population aged 65 years or older will be as high as 190 million, accounting for 13.5% of China's total population [3]. In contrast, data published by the United Nations show that the average percentage of the world population aged 65 years or older in 2019 was only 9.1% [4]. (2) There are more patients with noninfectious chronic diseases (NCDs)--data show that the prevalence of NCDs in China was as high as 34.3% in 2018, with a prevalence rate of 52.3% for those aged 65 years or older [5]. Furthermore, the top four diseases in terms of mortality in China in 2020 were malignant tumors, heart disease, cerebrovascular disease, and respiratory diseases, all of which are NCDs [5]. Notably, they were also the top 10 causes of death in the world in 2019, resulting in approximately 33.2 million deaths [6]. It is evident that NCDs have a particularly harmful effect. (3) The proportion of health expenditure to gross domestic product (GDP) is low--in 2020, China's health expenditure occupied 7.12% of the GDP, while those of developed countries such as the United States, the United Kingdom, Japan, and Australia generally exceeded 10% [7; 8]. Therefore, the Chinese government has to being investigating how to build a new medical and health service system. In this context, in order to meet the medical and health needs of more residents without reducing the quality of medical care, the Chinese government has decided to accelerate the construction of the \"Internet medical system\". As a result, since 2018, the Chinese government has introduced a series of polices to promote the development of Internet medical services, such as \"The Opinions on Promoting the Development of \"Internet plus Medical Health\"\", \"Guidance from National Healthcare Security Administration on improving the price of \"Internet plus\" medical services and medical insurance payment policies\" [9; 10]. Under the dual influence of market demand and national policy guidance, as products of the in-depth integration of \"Internet\" and \"medical and health services\", Chinese online health communities, such as \"Good Doctor Online\", \"Chunyu Doctor\", and \"We Doctor\", have developed rapidly. They are favored by many Chinese users and patients because of their low costs, the diversity of medical services available, and the convenience of the communication between doctors and patients [2; 11; 12]. In June 2021, the number of online medical users in China reached 239 million, accounting for 23.7% of the total number of netizens in China (Figure 1) [13]. Online Health Communities (OHCs) refer to the virtual communities whose main function is to exchange medical and health information or who have both online medical and online social functions. There are three types of OHCs: Patient to Doctor (P2D), Patient to Patient (P2P), and Doctor to Doctor (D2D). When using online health communities, users engage in various forms of information behavior, such as information searching, information adoption, and knowledge sharing [14; 15; 16].