We examined how long working hours were associated with MI in China for the period 2014–2018. Our regression analysis based on three-wave longitudinal data and dynamic models with the lagged working hours variable indicated that long working hours had a significant positive association with MI. The basic results are aligned with the findings of previous cross-sectional studies in the context of China [21, 22], which did not fully control for statistical biases; however, the OR values are higher in this study. These findings can contribute to the literature on the association between long working hours and mental health and provide richer and more robust conclusions. These estimation results shed light on the association between long working hours and mental health in-depth as follows:
First, the estimation results in this study confirmed that long working hours may increase the probability of MI. The magnitude of the OR ratio coefficients (1.12–1.22 in Table 2) is smaller than those in other studies for China (1.745) . The differences may be attributable to the different data and models: we used the three-wave national longitudinal survey data from 2014–2018, and the dynamic lagged variable model to address the initial dependent and reverse causal problems, whereas previous studies used one-point cross-sectional survey data and did not address the bias in estimations. To compare the effects of long working hours on MI between China and other countries, according to a meta-analysis , the effect is smaller for China than for the other Asian countries, such as Japan (1.333) and Korea (1.237), and Italy (1.341), Spain (1.248), and the United States (1.274), but greater than that for Denmark (1.091), Finland (1.063) and the United Kingdom (1.083). The international comparison results indicated that the institutional and cultural differences among countries may affect the effects of long working hours on mental health, which should be analyzed in detail in the future.
Second, the results indicated that the negative effect of long working hours on mental health was modestly more significant for women than for men; it may be because of gender differences in familial responsibility. Although the Chinese government has promoted gender employment equality in the labor market, women typically bear higher family responsibility (e.g., childcare, parent care, housework) than men [31, 32]; the double shift (long working hours followed by long housework hours) may lead to more family–work conflict for women than men, thereby enhancing the negative effect of long working hours for women.
Third, a disparity existed in the effects of long working hours among various educational and occupational groups. The results indicated that the negative effect of long working hours on mental health was greater for the highly-educated or white-collar workers than their counterparts (middle-and low-education, pink- and blue-collar groups). This may be because of the differences in job content between these groups: highly-educated or white-collar workers may face challenges in terms of addressing changes in the environment or fostering innovation, thereby increasing their work stress, whereas their counterparts primarily work routine jobs [12, 13, 33, 34].
Based on the results of this study, we can argue that, in general, policies to reduce long working hours may improve the Chinese population’s mental health status. First, although the Labor Law of the People’s Republic of China mandates that the standard work hours be less than 40 hrs weekly, the proportion of workers who worked for 50 hrs or more was 46% based on the CFPS data from 2014 to 2018, suggesting that a compliance problem remains in most Chinese companies. Working hours were reported to be longer in China, especially for privately-owned companies [23–24]; therefore, first, monitoring the compliance of regulatory policies regarding working hours in companies (especially privately-owned) should be considered. Second, policies to reduce long working hours or provide more social services to reduce the housework burden for women (e.g., providing more public kindergartens) may contribute to improving their mental health status. Third, unlike in most developed countries (e.g., Japan), there is no mental health counseling branch in most Chinese companies; the policy to promote the establishment of a mental health counseling center at the workplace is expected to improve mental health status in China. Finally, as the negative effects of long working hours differ by group, these policies should be aimed more toward women, highly-educated, white-collar, and younger workers.
This study has several limitations. First, although we used dynamic models with lagged long working hours variables, we could not identify the underlying causality of long working hours affecting mental health, which should be investigated in a more in-depth analysis. Second, as no policy reform existed for working hours during 2014–2018, we could not investigate the policy effect on the association between long working hours and mental health based on a quasi-experimental method, which can be addressed in future research.