An analysis of social participation and depression in middle-aged and senior citizens in China: A xed-effect analysis

Social activities has been suggested to prevent for depression for middle-aged and senior citizens for a long time. However, researchers failed to reach an agreement on the inuence of formal and informal social activities on depression for both males and females. This study aimed to investigate the difference between these two types of social activities on depressive symptoms in middle-aged and senior citizens for both males and females in China. Based on activity theory, social activities are classied into formal social activities and informal social activities according to the degree of intensity and intimacy. A total of 8610 participants from an 8-year period of the Chinese Health and Retirement Longitudinal Study (2011–2018) were analyzed using xed-effect analysis. 10-item center for Epidemiologic Studies Depression Scale was used to measure depression symptoms for middle-aged and senior citizens.


Introduction
Depression is one of the leading public health problems globally because of its serious in uence on people's health [1]. More than 264 million people of all ages suffer from depression [2]. Speci cally, depressive symptoms can predict numerous adverse health outcomes, such as obesity [3], frailty [4] and type 2 diabetes [5]. Moreover, depression is also a major contributor to suicide cases, which is close to 80,000 pers year, and caused disability in 50 million people [6], causing heavy psychological burden not only to the sufferer, but also to their families and to the whole society.
In addition, the prevalence of depression starts reaching signi cant levels in middle-and old ages [7].
Depression is even steeper in low-and middle-income countries. Over 80% of this disease burden occurred in low-and middle-income countries (LMICs) [6]. Moreover, 76% to 85% of people in LMICs receive no treatment for their disorder due to insu cient professional resources of treatments [2]. China, one of the low-and middle-income countries, has the largest population in the world and is experiencing severe aging, with 41.4% of the population aged 45 and above [8]. What's more, 30% of males and 43% of females suffered from depression symptoms among residents aged 45 and over in China as measured by 10-item center for Epidemiologic Studies Depression Scale (CESD-10) [9], which indicates the urgency of nding a population-based strategy to prevent depression for this big vulnerable group in China. Social participation has become a widely studied way to protect against depression due to its low cost, wide accessibility and no side effects compared to drug therapy [10]. Previous studies have explored the impact of certain kind of social activities on depression, such as talking with friends [11], participating in volunteer activities [12] and dancing [13]. Previous researches have also studied how various kinds of social activities in uencing depression level in different ways [7,14]. However, these studies always ignore the theoretical logic of the effect of social participation on depression.
As activity theory suggested, middle-aged and senior residents tend to lose previous identities because of retirement or other variations in life. Social participation is one of the most effective ways to help older generation to attain a new social role support or reinforcement [15]. Therefore, social activities can protect them against depression. More speci c role supports come from higher frequency and more intimate social activities [16]. Thus, engaging in more intimate and intense social activities may increase life satisfaction more and thus be more effective in preventing depression [17]. Considering such important characteristic of social activities, some studies have divided social activities into informal social activities and formal social activities based on its intensity and intimacy. Informal social activities are believed to have greater role feedback because it is focus on emotional function and thought to be based on major group relationships such as family, friends and neighbors [18]. In contrast, formal activities are organized by formal organization, such as volunteer group and they always focus on achieving speci c goals [19]. However, researchers failed to reach an agreement on the in uence of these two types of social activities on depression [20,21]. Considering the in uence of formal and informal social activities on depression were inconclusive due to different regional cultures [7], it is necessary to explore this relationship again a different cultural context and add some new insights for protecting middle-aged and seniors against depression.
However, as the key mechanism played in social activities and depression of this paper is based on activity theory (20). The roles related to the participants are as important as the characteristics of social activities [22]. In this paper, we will consider the gender factor due to the following considerations: It is generally accepted in academia that women are more likely to suffer from depression than men [23].
Second, from the perspective of activity theory, the reason that social activities can prevent elderly from depression is participating in social activities can help people gain role support and role reinforcement.
However, women born prior to the 1970s were more likely to be a housewife in China [24], thus their roles won't change dramatically compared to men. Third, in general, men and women have different social networks, women tend to recognized many people as their friends and man tend to have a few close friends [25,26]. There is also existing evidence indicating a different relationship between types of social activities and depression between male and females [20,21]. In order to make better use of social activities as a tool to protect middle-aged and senior residents against depression, the relationship between types of social activities and depression in men and women needs to be studied separately.
In sum, this study was conducted with three aims: 1) To get a preliminary understanding of depression of middle-aged and senior citizens with different genders. 2) To increase our understanding between different types of social activities and depressive symptoms from the perspective of considering the intimacy and intensity of social activities. Furthermore, to eliminate endogenous interference, we use a xed effect analysis.

Sample and data collection
The data used in the present study was derived from China Health and Retirement Longitudinal Study occasionally or a moderate amount of the time; and Most or all of the time" as 0,1 ,2 and 3 respectively. The question of (5) and (8) are positive items and they were reverse-coded. We added them together and got the CESD score. People with higher score are more likely to be considered as depressed. We checked the internal consistency of the CESD-10 scale in our sample, and the Cronbach's α=0.792.  [7]. We also used an important dummy control variable to indicate whether the respondents had experienced the loss of a child (children). The detailed information about data de ning and data processing are shown in Table 1. In order to further verify whether our model is reasonable, we made a series of tests. the first analysis we conducted was the F test, the results of F test showed that p<0.001, which indicated the fixed effect model is better than pooled ordinary least square. Then we used Hausman test to test whether fixed effect model is better than random effect model. The results also showed that p<0.001. Thus, we still use fixed effect model.

Data description in wave 1
Table 2 displayed the basic characteristics of all respondents and comparisons between citizens who are females and males in wave 1. The average age of all respondents in wave 1 was 57.9 years old. If we set depression scores above 10 points as a threshold for depression as previous literature suggested [21], we found the depression rate of these participants was 36.2%. Among 8610 participants, there were 65.2% (n=7084) participants lived in rural areas. A greater proportion of participants were partnered (90.0%), female (53.8%), still working (75.6%), with rural hukou (82.3%), with primary education level or lower (66.9%), living with child (60.5%), thinking themselves healthy (74.0%), having not experienced losing a child (children) (92.3%), and not participating social activities (50.6%). The participants in wave 1 were more likely to participate in informal activities than formal activities (46.9% vs. 2.5%). The average number of chronic diseases of the participants was 1.40.
More detailed comparisons between males and females were listed in Table 2.  Table 3 showed the proportion of informal and formal social activities among men and women participants in all four waves. Compared with females, males were more likely to participate in formal activities in the first three waves (p-value<0.001). Participants who were females had a lower probability of participating in formal activities in wave four, but the difference is not significant (p-value=0.102). Comparisons between male and female groups show no statistical differences in participation in informal social activities among four waves (p-value>0.05 for all four waves).

Regression results
To get the effect of types of social activities on depression scores, we conducted fixed effect regression analysis with robust standard error. The results of regression are shown in Table 4. As we can see in Table 4, column (1) displays the estimates for the full sample. Subsample analyses by gender and registered residence are presented in the following column. From column (1) in Table 4, we found that, after controlling for other variables, participation in informal activities was associated with a decrease in depression score of approximately 0.239 in the full sample (p-value<0.01). We found that depression score has a significantly positive relationship with age. Particularly, an increase in age of one year was associated with an average increase of 0.030 in depression scores. column (4) and column (5) showed that informal social activities can significantly benefit both females and males (p-value<0.05 for females and P<0.01 for males). As we can see from column (4), for female participants, the group that took part in informal social activities was associated with a 0.189 lower depression score than the group that not. For male participants, men who participated in informal social activities had depression scores 0.307 points lower than those who did not. We found -0.307 is significantly smaller than -0.189 (p-value<0.01). We couldn't find any significant relationship between formal activities and depression score in all models (p>0.1).

Robustness analysis
We undertook robustness analysis by excluding the variable whether the participant took part in formal social activities. The results are shown in Table 5. Results shown in Table 5 were largely consistent with our original analyses, which could support the robustness of the reported findings. Note: *** p<0.01, ** p<0.05, * p<0.1.

Informal and formal social activities
Social activity has been one of the most widely studied non-pharmacological approaches to depression prevention [19,21]. This paper examined the relationship between types of social activities and depression symptom among different groups of middle-aged and older people in China. We found a signi cant relationship between informal social activities and depression in all groups. However, we did not nd a signi cant relationship between formal social activities and depression in any group. Similarly, previous studies also only found a relationship between informal social activities and life satisfaction [21]. According to activity theory, older people tend to nd their new roles from participating social activities [29]. Thus, social activities can protect them against depression caused by role loss. Since the classi cation of informal activities and formal activities is based on different degrees of intimacy and intensity, informal activities can lead to more intimate relationships and higher frequency of participation. Thus, people can get higher social support from informal social activities, which reduces depression scores more effectively. Meanwhile, as we can be seen from Table 2, in each wave, more than 40% of our participants have participated in informal social activities, while less than 10% of them have participated in formal activities, so above relationship between formal social activities and depression may be caused by the low statistical power due to low participation in formal social activities.

Gender difference
Young Bum Kim used Hallym Aging Panel Data to explore the relationship between different types of social activities and the morale of people aged 54 and over in South Korea. He found that participating in informal activities only bene ts women and participating in formal activities only bene ts men [30].
Unlike that study, we found different results in Chinese context. We found a negative relationship between informal social activities and depression scores in both men and women, we didn't nd signi cant relationships between formal activities and depression score in both men and women group. And we found the coe cient of informal activities in larger in men than women, which means the informal social activities is more effective for men. We have two explanations for above results: First, in China, informal social activities involve communication with friends, women tend to compare themselves with their friends when they communicating with them while men are more likely to solve practical problems when interacting with their friends [25,26]. Second, men tend to retire from full-time jobs and careers; However, many women spend their retirement in less dramatic ways, they will either doing housework or working part time because of Asia's male-dominated culture [30,31].Thus, males can bene t more from participating in informal activities.

Strengths and limitations
To the best of our knowledge, this paper is the rst to study the effect of social activities on depression symptom from the perspective of activity theory in China. We examined the different effects of informal and formal social activities on depression in middle-aged and senior Chinese and used xed effect model that rules out the in uence of potential endogeneity. The study found that informal social activities lowered depression scores among the whole sample. Meanwhile, this study is also one of the few studies to include all males and females in Chinese scenario. The ndings of this paper reveal some differences between male and female participants. The results showed that males and females will both bene t from the informal social activities. The results of our study also imply that role change is also important to understand the relationship between social activities and level of depression.
The results of this study should be interpreted with caution due to the following limitations: First, considering that the survey we used was conducted every two or three years, the in uence of the social activities on depression would fade with time. Thus, we could not adopt a lagged model. Second, with xed effect model, we can't include variables that constant with time. Third, the sample size of respondents who participated in formal activities is small, we can do this study in a context where formal activities are more common in the future. Fourth, we only considered gender difference in this paper. Future studies can consider to examine other factors that could in uence the outcome, such as place of residency and education.

Conclusion
In summary, this study investigates the relationship between social activities and depression symptom from a new perspective by applying activity theory into analysis. We have following main ndings: First, women have higher depression scores and participates fewer social activities than men. Second, not all types of social activities are useful, the participants should be treated differently according to various characteristics. Formal activities had no effect on depression scores of middle-aged and senior residents. Informal activities can bene t to both groups of participants. Our study can help practitioners who provide services for the elderly to better take care of the elderly's psychology. For example, under the current home-and community-based care service model, this study provides some insights on how to provide spiritual consolation for the elderly.