Association between exercise variations and depressive symptoms among precarious employees in South Korea

Research regarding the association between depression and exercise has been limited regarding precariously employed individuals. The current study investigated the association between

exercise variations and depressive symptoms among precarious employees in South Korea. Data from the 2014, 2016, and 2018 Korea National Health and Nutrition Examination Survey (KNHANES)

were analyzed. In total, 13,080 participants aged ≥ 19 years responded to the survey. The Korean version of the PHQ-9 was utilized in addition to questions assessing regular exercise.

Precariously employed men engaging in two or more variations of exercise each week were significantly less likely to report depressive symptoms (adjusted (OR): 0.78; 95% CI 0.62–0.97; p = 

0.025), and the likelihood of depression was also lower for women who engaged in one or more forms of exercise (adjusted OR: 0.82; 95% CI 0.71–0.94; p = 0.006). These findings support the

association between depression and exercise and suggest that greater variations in regular exercise are associated with a reduction in depression for men whereas any form of exercise reduces

the risk of depression in women.

Employment stability has been a significant contributing factor in socioeconomic status, which directly influences one’s health status1. Precarious employment is considered as a determinant

of health, as it not only influences the health and well-being of employees but also their families and associated communities2. The negative effects of precarious employment have been

associated with a higher prevalence of mental health conditions including depression and anxiety3, 4, in addition to reduced health-related quality of life5. Such mental health consequences

have become one of the greatest health problems leading to the global socioeconomic burden6, 7.

Depression may affect a person’s well-being in addition to impairing daily and professional functioning8. Furthermore, depression can not only directly result in considerable costs including

healthcare services, but it can also have an indirect and substantial impact resulting in reduced productivity, work capacity, and even early retirement9, 10. Studies on depression among

employees have shown that depression is a major cause of long-term sickness absence11. Thus, studies have highlighted the importance of health promotion including counseling services, stress

management, and improvement in work environment settings to prevent depression among employees, although these have only displayed minor effects12. Furthermore, work-directed interventions

including work adjustments and additional coaching provision have also demonstrated promising outcomes13.

Reduced physical activity is determined to be one of the main features of depression and is included in the diagnostic criteria of depression14. Previous research has suggested that exercise

may play a role in the reduction of depression15; thus, numerous studies have focused on physical activity interventions to reduce depressive symptoms, at least within the clinical

population16, 17. Supervised strength training have also demonstrated positive effects on depression in comparison to relaxation18, whereas aerobic exercise did not demonstrate any

effects19. Likewise, recent research suggests that anaerobic exercise also helps to reduce depressive symptoms20.

Nonetheless, longitudinal studies have failed to identify the consistent effects of physical exercise on the psychological symptoms of the general population17. Moreover, whilst studies have

assessed workplace exercise interventions to reduce the risk of depression among sedentary employees and improve work-related outcomes such as the increase in work attendance and reduction

of job stress21, these were mostly focused on permanent employees, without the consideration of factors surrounding precarious employment8. As a result, many aspects of how physical exercise

prevents depression remain unclear22; with almost no studies to show the impacts of exercise among precarious employees.

Beyond the existing bilateral relationship between exercise and depression, previous research has demonstrated the efficacy of various exercise combinations in greatly improving physical

health as compared to engaging in no exercise or only a single type of exercise23, 24. Therefore, the following study will investigate whether a combination of different exercises will have

subsequent effects on the levels of depressive symptoms among precariously employed individuals in the South Korean population.

In addition, sleep plays a vital role in maintaining homeostasis and also enhancing mental and physical well-being25. However, sleep disturbances are typical among most depressed individuals

with studies demonstrating a strong bilateral association between sleep and depression26. Additionally, many precarious employees are at risk of such sleep disturbances due to their work

hours and also insecurities27, 28. Henceforth, understanding the importance of sleep on one’s well-being, the association of sufficient sleep and depressive symptoms will also be evaluated

for the current study.

Among the participants, 12.0% of men and 19.7% of women scored 5 or above on the PHQ-9 scale for depressive symptoms. Both men and women who engaged in more variations of exercise reported a

reduced prevalence of depressive symptoms in comparison to those not engaging in regular exercise. Among men, those who reported excessive amounts of sleep demonstrated the greatest

prevalence of depressive symptoms in comparison to insufficient and normal levels of sleep (20.4% vs. 12.0% vs. 11.1%, p = 0.026). However, those with insufficient sleep had highest

depressive symptom scores, followed by excessive and then normal levels (20.5% vs. 19.5% vs. 16.9%, p = 0.005) for female employees. Overall, both men and women with depressive symptoms

reported lower levels of educational attainment, lower household income, current smokers, more likely to be unmarried and be diagnosed with a metabolic syndrome. While there was no

significant difference according to residential area among men, for women, those living in rural areas reported a greater prevalence of depressive symptoms (21.6% vs. 19.3%, p = 0.048). The

details are provided in Table 1.

Multivariable logistic regression was conducted to evaluate the association of depressive symptoms with exercise variations, as demonstrated in Table 2. Precariously employed men engaging in

two or more variations of exercise each week were 0.78 times less likely to report depressive symptoms (adjusted Odd Ratio (OR): 0.78; 95% CI 0.62–0.97; p = 0.025), thus representing the

association between exercise and the reduction of depressive symptoms. However, women who engaged in even just one form of exercise reported a reduced likelihood of depression (adjusted OR:

0.82; 95% CI 0.71–0.94; p = 0.006), as well as those engaged in two or more variations of exercise (adjusted OR: 0.72; 95% CI 0.62–0.83; p