2.1 The direct effect of increased government attention to aging

Government attention to aging issues directly impacts middle-aged and elderly mental health through two channels: policy implementation effects and signal effects.

2.2 The indirect effect of increased government attention to aging

Government attention to aging indirectly improves middle-aged and elderly mental health through four mechanisms:

3.1 Empirical design

Based on the theoretical analysis above, this paper constructs a multidimensional fixed effects model as the benchmark econometric model:

(1)

In equation 1 i and t represent the sample individuals and observation years, respectively. is the dependent variable, representing the degree of depression among middle-aged and elderly people; is the independent variable, representing the degree of government attention to the aging issues; denotes control variables at the household and city levels; , , are the parameters to be estimated.

represent fixed effects for year, household, and city. The purpose is to control for the impact of non-time-varying factors at the household and city levels on the degree of depression among middle-aged and elderly people, while also controlling for the impact of time-varying factors such as macroeconomics that do not change with individuals, thereby reducing the potential impact of omitted variables. is the standard error clustered at the household level, as there may be some unobserved factors at the household level that affect all members of the household. By clustering at the household level, the impact of these factors on the estimation results can be controlled to a certain extent.

3.2 Data description

The sample data for this study primarily originates from municipal government work reports, CHARLS, the China Urban Statistical Yearbook, and the CNRDS database. Since CHARLS data collection began in 2011, surveys have been conducted biennially. This study selects individuals aged 45 and above as the research population. Through data screening, cleaning, and matching, we obtained five waves of panel data covering 115 prefecture-level cities, 18,342 households, and 35,637 individuals (35,637 represents the total sample size of all observations used in the regression analysis) across China for the years 2011, 2013, 2015, 2018, and 2020. Descriptive statistics for each variable are presented in Table 1.

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Table 1. Descriptive Statistics.

https://doi.org/10.1371/journal.pone.0337347.t001

The CHARLS is a high-quality micro-dataset representative of households and individuals aged 45 and above in China. The CHARLS national baseline survey was conducted in 2011, covering approximately 17,000 individuals from about 10,000 households. We primarily utilize data from five waves spanning 2011, 2013, 2015, 2018, and 2020 for our analysis. This study adhered to the ethical principles outlined in the 1964 Helsinki Declaration and its subsequent amendments. The data used in this study were retrieved from the CHARLS. This survey was endorsed by the Biomedical Ethics Committee of Peking University (NO.IRB 00001052–11015). All participants in the survey signed or marked (if illiterate) the informed consent forms. All methods were carried out in accordance with relevant guidelines and regulations.

3.3 Independent variable: Government attention to aging

Developing a scientifically sound government attention index helps comprehensively and accurately assess macro policy impacts on middle-aged and older adults’ mental health. Existing studies often extract term frequency or occurrence rates related to relevant policy areas from government work reports and other guiding documents as indicators of policy intensity or attention. While this method reflects policy emphasis in specific areas, relying solely on word frequency proportions may overlook context, semantics, and sentence meaning in policy texts, leading to measurement biases.

Therefore, this paper adopts the measurement methods for government attention proposed by Oster et al [29]. We manually collected government work reports from prefecture-level cities across China from 2011 to 2020. Using word segmentation technology, we screened 56 keywords related to aging, including aging, elderly care, retirement, and silver economy. We extracted the number of characters in keywords and their sentences, calculating their proportion of total characters in government work reports. This approach effectively reflects government attention to aging issues while preserving semantic and syntactic meaning of original texts, reducing information loss from simple word frequency counting. Additionally, to avoid duplicate counting errors, sentences containing multiple keywords are counted only once in statistics. Since local government work reports are typically released at the beginning of the year while actual government activities span the entire year, this indicator has strong exogeneity, largely avoiding endogeneity caused by reverse causality and enhancing the reliability of empirical analysis.

3.4 Dependent variable: Degree of depression

The dependent variable is depression severity among middle-aged and older adults, calculated based on the depression scale (CES-D) in the CHARLS data collected from 2011 to 2020. The scale includes 10 items designed to assess respondents’ mental health status, such as I get annoyed over small things and I have difficulty concentrating on tasks. Each item is categorized into four levels based on occurrence frequency: never (<1 day), not very often (1–2 days), sometimes or half the time (3–4 days), and most of the time (5–7 days). Depression scores are calculated according to standard criteria, with the four levels scoring 0, 1, 2, and 3 points respectively. Items 5 (I am hopeful about the future) and 8 (I am happy) are reverse-scored, resulting in total scores ranging from 0 to 30 points.

3.5 Other variables

This paper uses basic characteristic variables at the household or individual level as control variables, including age, years of education, marital status, gender, household registration, healthcare expenditure, and number of children. Additionally, we select socioeconomic characteristic variables at the city level as control variables, including sulfur dioxide emission intensity to measure environmental quality, GDP and fiscal expenditure to measure economic development levels, and the number of hospitals, licensed or assistant physicians, and hospital beds to measure public service levels.

According to the theoretical analysis, mechanisms through which government attention affects middle-aged and elderly mental health include environmental improvement, social welfare, family support, and lifestyle. We select relevant variables to measure these aspects: Environmental improvement: We use urban wastewater and particulate matter emission intensity to measure water pollution and air pollution in cities. Social welfare: We use total transfer payments received by respondents in CHARLS data as a measure. Family support: We measure family care using annual economic support provided by adult children to elderly individuals and the frequency of adult children visiting elderly parents from CHARLS data. For asset allocation, we calculate family savings rates and debt ratios. Lifestyle: This includes frequency of elderly participation in social activities, cultural and sports activities, and sleep duration.

The data processing for the variables (Table 1) is as follows: Individual-level variables: (1) Age: Calculated by subtracting the respondent’s birth year from the survey year. (2) Years of education: Assigned based on the respondent’s educational attainment level. When the individual education level is coded as 1–11, the corresponding years of education are 0, 3, 3, 6, 9, 12, 16, 15, 16, 19, and 22, respectively. (3) Gender: Coded as 1 for male respondents and 2 for female respondents. (4) Social interaction: Measured by the frequency of social activities. (5) Entertainment activities: Measured by the frequency of entertainment activities. (6) Sleep duration: Measured by daily sleep hours. (7) Medical expenditure: Represented by the logarithm of household medical expenses. (8) Social welfare: Measured by the total amount of transfer payments received. (9) Frequency of children visiting parents: First, the original data was reverse-coded using a 1–10 scale, where higher values indicate more frequent parental visits by children. Second, for families with multiple children, the frequency values were summed and averaged to obtain the mean frequency of children visiting parents. (10) Economic support: Measured by the annual financial support pro-vided by adult children to their parents. (11) Urban-rural classification: Represented by a binary variable, where 0 indicates rural areas and 1 indicates urban areas. Household-level variables: (1) Household savings rate: Calculated as the ratio of household savings to financial assets. (2) Household debt ratio: Calculated as the ratio of household debt to financial assets.

4.1 Baseline regression results

To examine the impact of government attention to aging issues on the mental health of middle-aged and elderly people, a fixed-effects model is used for benchmark regression analysis. Column (1) controls only for basic variables at the individual level, and the results show a significant negative correlation between government attention to aging issues and the degree of depression among middle-aged and elderly people. This indicates that, without controlling for other potential con-founding factors, local governments’ attention to aging issues helps alleviate depression symptoms among middle-aged and elderly people.

In columns (2) to (4), the model sequentially introduces year, household, and city fixed effects to control for the impact of time trends, unobservable factors at the household level, and inter-city heterogeneity on the estimation results. Regardless of which fixed effects are controlled for, the coefficient for government attention remains negative and statistically significant, indicating that this effect is robust. Notably, after incorporating household and city fixed effects, the coefficient for government attention further expands, suggesting that the positive impact of government policy attention on the mental health of middle-aged and older adults remains valid under stricter identification conditions, and may even be strengthened.

In summary, government attention to aging issues is significantly associated with lower levels of depression among middle-aged and older adults, and this relationship remains robust after controlling for potential confounding factors.

4.2 Analysis of heterogeneity in middle-aged and older adults

Heterogeneity analysis indicates that the impact of government attention to aging issues on the degree of depression among middle-aged and older people varies significantly across gender and living environments (Table 2).

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Table 2. Baseline regression results.

https://doi.org/10.1371/journal.pone.0337347.t002

In terms of gender, the mitigating effect of government attention on depressive symptoms is significant among men but not among women. This difference may stem from differences in social support mechanisms: men are less likely to express their emotions in traditional culture, and the institutional and emotional support conveyed by government policies have a greater buffering effect on their psychological state. Women’s mental health, however, may be more influenced by factors such as family relationships, social role identity, and social support. Relying solely on government policy support is not sufficient to significantly improve their mental state (Fig 2).

In terms of place of residence, government attention has a significant mitigating effect on the degree of depression among rural middle-aged and elderly people, but no significant effect on urban populations. Possible explanations include: (1) Differences in public resources allocation: Rural area generally lag behind in social services and infrastructure. Government attention to aging issues and the implementation of corresponding policies can effectively compensate for the shortage of public resources in rural area, providing critical support for rural middle-aged and elderly people. In contrast, urban residents already have a relatively well-developed social security system, and marginal policy attention has a relatively limited impact on their mental health. (2) Differences in the causes of psychological stress: Urban middle-aged and elderly people may face more complex psychological stressors, such as the fast pace of urban life, weakened social connections, rising living costs, and feelings of loneliness brought about by urbanisation. Addressing these issues often requires comprehensive, multi-level, and cross-departmental interventions, and single-policy attention alone is unlikely to achieve substantial improvements (Fig 2).

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Fig 2. Heterogeneity analysis results. Notes: This figure presents the heterogeneous effects of government attention to aging on elderly mental health across gender and urban-rural classifications. The x-axis shows point estimates and 95% confidence intervals. Data are primarily sourced from the CHARLS data collected from 2011 to 2020, and government work reports. Figure 2 was compiled based on CHARLS data.

https://doi.org/10.1371/journal.pone.0337347.g002

4.3 Environmental improvement mechanism

To further explore how government attention affects the mental health of middle-aged and elderly people through environmental improvement mechanisms, this paper selects urban wastewater discharge intensity and smoke and dust emission intensity as key indicators of environmental quality. The regression results shown in columns (1) to (2) of Table 3 indicate that, increased government attention to aging issues significantly reduces the emission levels of these two types of pollutants, thereby improving environmental quality. These results indicate that while paying attention to the aging issues, the government has strengthened its efforts to control water and air pollution.

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Table 3. Mechanism Analysis: Environmental Improvement, Social Welfare, and Family Support.

https://doi.org/10.1371/journal.pone.0337347.t003

Water pollution poses a direct threat to the health of middle-aged and elderly people, particularly in terms of drinking water safety and living environments. With increased government attention, more resources have been allocated to wastewater treatment and water quality improvement, effectively reducing health risks associated with water pollution. Similarly, air pollution, especially particulate matter, poses a significant threat to the fragile respiratory systems of middle-aged and elderly people. Government policies have played a key role in reducing air pollutant emissions, thereby lowering the likelihood of middle-aged and elderly people developing respiratory diseases.

In summary, this mechanism ultimately helps to improve the overall health of middle-aged and elderly people and alleviate their feelings of depression [55–57]. Government attention indirectly improves the mental health of middle-aged and elderly people through environmental improvements.

4.4 Social welfare and family support

The results in columns (3) to (5) of Table 3 reveal the mechanisms of social welfare and family support in the process of government attention influencing the degree of depression among middle-aged and elderly people. The study finds that increased government attention to aging issues significantly increases the level of social welfare received by middle-aged and older adults and the frequency of visits from their adult children.

In terms of social welfare, this paper measures it by the total amount of transfer payments received by respondents. Higher total transfer payments indicate better social welfare for respondents. On one hand, this can meet the production and living needs of respondents and their families, raise their standard of living, and reduce their concerns about production and daily life, thereby alleviating depressive symptoms. On the other hand, higher total transfer payments enable respondents to better address physical and mental health conditions, lessen their suffering, and thus mitigate depressive symptoms. Therefore, enhanced social welfare effectively alleviates depressive symptoms among respondents [56,58,59].

In terms of family support, this study measures it through the annual financial assistance provided by children to their elderly parents and the frequency of visits made by children to their elderly parents. Although the government’s level of attention to ageing issues does not significantly influence the financial support provided by children, it does significantly increase the frequency of visits made by children to their elderly parents. Increased frequency of visits from children provides considerable psychological comfort to the elderly, significantly reducing their feelings of loneliness and thereby alleviating depressive symptoms. Therefore, enhanced family support effectively mitigates depressive symptoms among respondents [60–62].

However, it did not significantly affect the economic support provided by adult children. This result may be attributed to the following three factors:

1. (1) Substitution effect of economic support: As the government pays increasing attention to the issue of aging, social welfare such as pensions and medical insurance continues to improve. Middle-aged and elderly people can obtain more stable economic security through these public resources, thereby reducing their dependence on financial assistance from their adult children. Therefore, adult children do not need to provide additional financial support, as the public resources provided by the government, to a certain extent, have replaced the expenditure of family private resources.
2. (2) Stability of family support funds: Adult children’s financial support for their parents usually depends on the long-term economic situation of the family rather than short-term policy changes, which are relatively rigid. Factors such as family income structure, adult children’s employment and income levels have a more direct impact on the ability to pay support funds. Even if the government increases its attention and improves welfare, it is not enough to significantly change adult children’s financial support behaviour, especially when the family has already reached its spending capacity limit.
3. (3) The guiding role of policy advocacy and public opinion: The government’s concern for aging is reflected not only in economic investment but also in the promotion of family ethics and social responsibility. Through policy publicity, the promotion of filial piety culture and family care concepts, the government may indirectly encourage children to strengthen their emotional ties with their parents, as evidenced by an increase in the frequency of visits. The promotional effect of such non-material support on the mental health of middle-aged and elderly people should not be overlooked.

4.5 Family asset allocation

The impact of government attention on family support is also reflected in asset allocation. The results in columns (1) to (2) of Table 4 show that increased government attention to aging issues significantly increases household savings rates while reduces household debt ratios. This finding indicates that the government improves the financial decision-making behaviour of middle-aged and elderly households by alleviating their economic pressures, thereby enhancing household financial stability and health [63]. Specifically, possible mechanisms include:

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Table 4. Mechanism analysis: Household asset allocation and lifestyle.

https://doi.org/10.1371/journal.pone.0337347.t004

1. (1) Reducing economic uncertainty and risk exposure: Increased government attention is usually accompanied by expanded social welfare, improved medical insurance coverage and public services. These policies effectively alleviate the financial pressure on families in areas such as medical care and elderly care, allowing middle-aged and elderly families to no longer rely on loans or debt to maintain their basic livelihoods, and to have more resources available for savings.
2. (2) Enhancing economic security and future expectations: Greater government attention helps to enhance the economic security of middle-aged and elderly households, enabling them to hold more optimistic expectations for the future. This confidence encourages households to actively increase their savings in order to cope with potential emergencies or future expenditure needs, thereby achieving a more reasonable asset allocation.

Therefore, the government’s focus on aging issues not only plays a role in mental health, but also has a profound impact on the economic behaviour of families.

4.6 Lifestyle

Columns (3) to (5) in Table 4 show the impact of government attention on three indicators of the lifestyle of middle-aged and elderly people: social interaction, cultural and sports activities, and sleep duration. The results show that government attention significantly increases the frequency of social interaction and participation in cultural and sports activities among middle-aged and elderly people, but has no significant impact on their sleep duration.

1. (1) Expansion of social support networks: The government’s focus on aging has led to the investment and development of more community resources and social platforms, such as gatherings for the elderly, volunteer activities, and interest groups. Policy support has created more social opportunities for middle-aged and elderly people, helping to expand their social support networks, enhance their sense of social belonging, and thereby improve their psychological well-being [64,65].
2. (2) Positive interaction between physical and mental health: Government policies often encourage older people to participate in various cultural and sports activities, such as fitness, dancing, calligraphy, etc. These activities not only help improve physical health, but also bring spiritual satisfaction, effectively relieving psychological stress and reducing the risk of depression.
3. (3) The complexity of sleep problems and the marginal effects of policy: Sleep problems among middle-aged and elderly people are often caused by a combination of factors, such as physiological aging, chronic diseases, and changes in lifestyle. These issues require more comprehensive and medically oriented interventions. Although government attention can improve their quality of life and mental state, these interventions have limited impact on sleep disorders rooted in physio-logical factors and therefore do not significantly extend sleep duration.