Introduction
The recent aging of the population in South Korea has increased the middle-aged population aged 40–59 by approximately 13% from 14.76 million in 2010 to 16.81 million in 2020 (Statistics Korea, 2021). In particular, the proportion of middle-aged women was approximately 53%, which is higher than that of middle-aged men. Middle-aged women undergo menopause during this period, which is one of the most significant changes in their life cycle (Kim and Oh, 2017). Menopausal women experience physical and mental discomforts such as hot flashes, sleep disorders, and depression, which may lead to deteriorated quality of life (Park and Sin, 2015). Therefore, our society currently needs to pay attention to middle-aged women's health in addition to the aging problem and discuss measures to address these issues.
Sleep disorders increase the risk of diseases such as diabetes and heart disease and trigger inflammations, and are also associated with the accumulation of fatigue and increase in safety incidents, resulting in negative impacts such as increased burden of healthcare costs, decreased quality of life, and misuse of neuroleptic and medical drugs (Buscemi et al., 2006). According to a study conducted on adults in South Korea, 46.2% of women and 35.6% of men have sleep disorders (Lee et al., 2020). In particular, sleep disorders in middle-aged women are related to increased stress and the physical and psychological changes of menopause (Chung and Tang, 2006). Thus, appropriate measures are required to manage and promote the health of middle-aged women.
A decline in physical activity is considered one of the key factors that increase the incidence of chronic diseases and show relevance to premature mortality (Cho, 2017). The World Health Organization (WHO) recommends that adults aged 18 to 64 engage in at least 150 minutes of moderate-intensity aerobic exercise per week or in muscle-strengthening activities twice a week or more (WHO, 2022). Regular physical activity provides various health benefits, such as maintaining bone density, strengthening the cardiovascular system, and preventing depression (Park, 2022), while also playing a crucial role in maintaining and improving the health of menopausal women. However, most middle-aged women show low levels of physical activity aside from daily activities. Accordingly, urban gardening is proposed as a way to increase middle-aged women's participation in physical activity and form healthy lifestyle habits. Urban gardening refers to horticultural activities in urban areas, characterized by communing with nature while engaging in physical activity. According to recent studies, urban gardening in the community helps reduce stress and anxiety, increase fiber intake, and boost physical activity, thereby playing a crucial role in preventing various chronic diseases and mental health disorders (Litt et al., 2023).
Urban gardening has been acknowledged for its various effects in improving health, such as promoting physical activity, reducing stress, and providing emotional stability (Koay et al., 2020; Lee et al., 2020; Chalmin-Pui et al., 2021; Ward et al., 2022). Moreover, urban gardening is also known to contribute to increasing social interactions and promoting community spirit (Park and Lee, 2012; Hong et al., 2020; Kim et al., 2023).
However, there is insufficient research reporting the effects of urban gardening on the improvement of physical activity and sleep quality in middle-aged women. Therefore, this study aims to analyze changes in the levels of physical activity, stress, and sleep quality among middle-aged women who participated in an urban gardening program. Through this process, we aim to empirically review the effect of urban gardening activities on middle-aged women's health improvement and seek development and applicability of urban gardening programs.
Research Methods
Research site
Urban gardening was conducted at Hamjul Urban Agriculture Park located in Siheung, Gyeonggi-do. Hamjul Urban Agriculture Park is located between residential areas such as apartments and commercial districts like shopping malls. On approximately 1,500m2 of urban gardening space, there are 90 plots of private gardens, each 16.5m2 (about 5 pyeong) where vegetables such as lettuce, peppers, tomatoes, and eggplants can be cultivated, as well as educational and experiential gardens created and in operation. The participants in this study also created 20 plots in the size of 16.5m2 (about 5 pyeong) each for the urban gardening program.
Participants
We openly recruited 40 middle-aged women in their 40s-50s who had no prior experience with urban gardening. The participation of these women in the experiment was not subject to review by the Institutional Review Board (IRB). Thus, we selected the participants by having them submit consent forms to participate in the research. Among them, we included 20 women who expressed willingness to participate in urban gardening in the experimental group participating in the urban gardening program, and 20 other women in the control group not participating in the program (Table 1). By age, the experimental group included 13 women in their 40s (65%) and 7 in their 50s (35%), while the control group included 17 women in their 40s (85%) and 3 in their 50s (15%). By occupation, the experimental group consisted of 14 homemakers (70%), 2 self-employed, 2 office workers, and 2 others (10% each). The control group consisted 14 homemakers (70%), 5 office workers (25%), and 1 other (5%), with a high proportion of full-time homemakers in both groups. Regarding family composition, the experimental group included 3 women (15%) in 1-generation households (couples), 15 women (75%) in 2-generation households (couples and children), 1 woman (5%) in a 3-generation household (grandmother, couple, and children) and 1 woman (5%) in a single-person household. The control group included 2 women (10%) in 1-generation households (couples), 17 women (85%) in 2-generation households (couples and children), and 1 woman (5%) in a 3-generation household (grandmother, couple, and children).
Research design
The urban gardening program consisted of 12 sessions focused on regular gardening activities and program activities with participants. The program was implemented once a week for 2 hours each session from April to July 2023. The program content included physical activities such as digging, mixing compost and soil, and mulching with leaves for urban gardening cultivation, as well as activities aimed at improving diet and cooking using the produce from the gardens (Table 2). In the private gardens, vegetables and herbs were planted and cultivated, including 'Heukhwarang' lettuce, which contains 124 times more sleep-inducing 'lactucin' than regular lettuce (Ortiz et al., 2023; Sayson et al., 2024). Vegetables such as celery, peppers, tomatoes, and eggplants containing minerals such as tryptophan, calcium, and magnesium that help synthesize sleep hormones like melatonin, and herbs such as lavender and rosemary were planted and cultivated (Bursac et al., 2005; RDANIAS, 2021).
Survey items
Amount of physical activity
The amount of physical activity was assessed using the short form of the International Physical Activity Questionnaire (IPAQ). IPAQ is a tool developed by the WHO, and the Korean version of the short-form physical activity questionnaire validated by Oh et al. (2007) was used to assess the degree of physical activity. The self-reported short-form IPAQ questionnaire classified physical activity into high-intensity, moderate-intensity, and low-intensity activities performed for at least 10 minutes for 7 days before the survey, and asked participants to report the number of days per week and the average daily duration (in minutes) of each activity. The amount of physical activity was calculated in the metabolic equivalent of the task (MET-min/week) based on the scoring method provided by the IPAQ Research Committee. The calculation of physical activity (MET-min/week) was done as follows: "MET level of each activity (high-intensity 8.0, moderate-intensity 4.0, walking 3.3) × duration of activity (min) × frequency of activity per week", with total physical activity being Survey items.
Stress
The level of stress was assessed using the Korean version of the Perceived Stress Scale (PSS), developed by Cohen et al. (1983) and adapted by Park and Seo (2010). This tool evaluates the level of stress that an individual subjectively experiences in daily life. It consists of 10 items, with each item rated on a 5-point Likert scale in response to the question, "How often have you felt or thought this way during the last month?" (0 = 'Never', 1 = 'Almost never', 2 = 'Sometimes', 3 = 'Fairly often', 4 = 'Very often). Higher scores indicate higher levels of perceived stress (Cohen et al., 1983; Park and Seo, 2010). The reliability of the scale in this study was Cronbach's alpha .86.
Sleep quality
Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI) developed by Buysse et al. (1989) and the Korean version of the Pittsburgh Sleep Quality Index (PSQI-K) translated by Sohn et al. (2012). PSQI is a self-reported questionnaire consisting of 7 components that measure 'subjective sleep quality' (an individual's sleep quality over the last month), 'sleep latency' (the time taken to fall asleep), 'sleep duration' (the amount of sleep), 'habitual sleep efficiency' (the ratio of time spent sleeping while in bed), 'sleep disturbance', 'use of sleeping medication', and 'daytime dysfunction' (impairment in daily functioning due to sleep issues). Each component is scored on a scale from 0 to 3, with the total score ranging from 0 to 21. Higher scores indicate poorer sleep quality, and a score of 5 or higher is classified as 'bad sleepers'. The reliability of the Korean version, PSQI-K, was Cronbach's alpha .84 (Sohn et al., 2012), and the reliability in this study was Cronbach's alpha .71.
Data analysis
The collected data were analyzed using IBM SPSS Statistics 25. Descriptive statistics were used to analyze the general characteristics of the experimental group and the control group. The differences in dependent variables following the application of the program were analyzed using the independent samples t-test. The correlations between physical activity, stress, and sleep quality were analyzed using Pearson's correlation coefficient. Statistical significance was set at p < .05.
Results and Discussion
The effect of urban gardening on physical activity of participants
Table 3 shows the results of comparing the amount of physical activity (IPAQ) between the experimental group and the control group. Before participating in the program, the experimental group showed an average of 2663.50 MET-min/week, while the control group showed an average of 3297.90 MET-min/week. After 6 weeks of participation, the experimental group and the control group showed an average of 3251.90 MET-min/week and 3260.20 MET-min/week, respectively. Upon completion, the experimental group showed an increase to 3675.45 MET-min/week, while the control group showed a decrease to 2830.98 MET-min/week, but there was no statistically significant difference (p = .275).
A similar trend was observed for high-intensity activity. Before participation, the experimental group recorded 1184 MET-min/week, and the control group recorded 1740 MET-min/week. After 6 weeks of participation, the experimental group showed 1284 MET-min/week, while the control group showed 1224 MET-min/week. Upon completion, the experimental group increased to 1680 MET-min/week, while the control group decreased to 968 MET-min/week, though this was not statistically significant (p = .123 ). Low-intensity activities showed a similar trend as high-intensity activities. On the other hand, for moderate-intensity activity, there was an increase in the control group, whereas there was rather a decrease in the experimental group compared to before participating in the program.
The change in physical activity of the experimental group due to urban gardening did not show a statistical difference between before participation and after 6 weeks of participation, and between before participation and after completion. However, in low-intensity activity, the average increased from 775.50 MET-min/week before participation to 1407.45 MET-min/week upon completion, showing a statistically significant difference (p = .012).
For the experimental group, high-intensity and low-intensity activities increased along with the progress of the urban gardening program, leading to an increase in total physical activity. This was similar to the study results by Litt et al. (2023), where the amount of physical activity increased in the group participating in gardening activities. Regular physical activity is known to be effective in promoting health (Park, 2022). Since urban gardening activities are perceived not as an exercise but a part of leisure and may have effects on promoting health, it is necessary to conduct more detailed research.
The effect of urban gardening on stress of participants
Table 4 shows the results of analyzing the effect of urban gardening on the stress levels of the experimental group and the control group. Before participation, the experimental group showed a score of 15.30, while the control group showed a score of 13.00. After 6 weeks of participation, the experimental group's score decreased to 13.15, while the control group's score increased to 14.25. Upon completion, the experimental group's score further decreased to 12.05, whereas the control group's score increased to 14.50. In the comparison with the control group, although the experimental group's stress index continuously decreased unlike the increasing stress index of the control group, the difference was not statistically significant (p = .148).
A similar trend was observed in the assessment of subdomains.
As for the change in the stress index of the experimental group, there was a statistically significant improvement from before participation to after 6 weeks of participation (p = .013), and from before participation to upon completion (p = .028), with the score decreasing from 15.30 before participation to 13.15 after 6 weeks of participation, and then to 12.05 upon completion.
Litt et al. (2023) and Kim et al. (2023) have reported that gardening activities have positive effects on stress reduction among participants. This is in line with the findings of this study, implying that urban gardening programs may have some effect on reducing stress in the experimental group. Therefore, additional research is needed to explore this further in terms of program composition and duration.
The effect of urban gardening on sleep quality of participants
Table 5 shows the results of comparing sleep quality (PSQI) between the experimental group and the control group. In terms of sleep quality (PSQI) following participation in the urban gardening program, the experimental group showed a score of 6.25, and the control group showed a score of 6.45 before participation. After 6 weeks of participation, the experimental group's score was 6.65 and the control group's score was 6.95. Upon completion, the experimental group's score was 5.15, whereas the control group's score showed an increasing trend to 6.55. However, there was no statistically significant difference compared to the control group (p = .121).
However, change in sleep quality (PSQI) in the experimental group showed a decrease from 6.25 before participation to 5.15 upon completion with a statistically significant difference (P = 0.019). Moreover, in 'subjective sleep quality' perceived by individuals, which is a subdomain, the score decreased from 1.10 before participation to 0.80 upon completion, showing a statistically significant effect (p = .010). Regarding 'sleep latency', which refers to the time it takes to fall asleep, there were statistically significant improvements between before participation and after 6 weeks of participation (p = .025), and between before participation and upon completion (p = .004).
Park (2022) stated that middle-aged women's participation in physical activity is effective in improving sleep quality, and Lattal (2010) reported that continuous exercise improves sleep quality. Therefore, it can be inferred that maintaining physical activity through regular gardening in the program had a positive effect on sleep quality compared to the control group engaged in everyday physical activity. This implies that urban gardening interventions may have a positive effect on sleep quality. Kim and Oh (2017) reported that sleep quality in menopausal women is closely related to their quality of life. It is worth expanding the analysis to explore the relationship between the development and application of urban gardening programs designed to improve sleep quality and improvement in quality of life, in which case the results of this study can be used as foundational data.
Correlation between physical activity, stress, and sleep quality
Correlation analysis was conducted to explore the interrelationships among the variables used in this study (Table 6). As a result, there was a positive correlation between sleep quality and physical activity (r = 0.248, p < 0.01). In particular, moderate-intensity activity showed a higher correlation with sleep quality (r = 0.320, p < .001). This finding is consistent with Kim (2021), who reported that sleep disorders in adults are closely related to physical activity, stress, and drinking.
Sleep quality showed a significant positive correlation with stress (r = 0.499, p < .001), indicating that higher sleep quality leads to lower stress levels (Table 6). Stress also showed statistically significant correlations with the subdomains of sleep quality: r = 0.325 (p < .001) with sleep duration, r = 0.348 (p < .001) with sleep disturbance, and r = 0.359 (p < .001) with daytime dysfunction. These findings are consistent with previous studies, such as Kang et al. (2018) on nursing students and Cheng et al. (2012) on college students, which reported significant correlations between stress and sleep quality.
Therefore, the results of this study suggest that maintaining an adequate amount of physical activity and reducing stress can play an important role in improving sleep quality. This finding indicates that further research can develop specific interventions to improve sleep quality by exploring how various subdomains of sleep quality interact.
Conclusion
This study analyzed the effect of urban gardening on physical activity, stress, and sleep quality in middle-aged women. The results showed that the experimental group who participated in the urban gardening program showed an increase in physical activity and a significant improvement in sleep quality. These findings suggest that the increase in regular physical activity through urban gardening and the reduction in stress through interaction with nature contributed to the improvement in sleep quality among middle-aged women. Although the stress levels of participants in the gardening program tended to decrease with their participation, this was not statistically significant. This might be due to limitations such as the program's duration, intensity, and sample size, which must be improved in future research.
As a result of analyzing the correlations among variables used in this study, there was a positive correlation between sleep quality and physical activity (r = 0.248, p < .01), especially with moderate-intensity activity (r = 0.320, p < .001) showing a higher correlation with sleep quality. Sleep quality also showed a relatively strong positive correlation with stress, which is consistent with previous research indicating that there was a significant correlation between stress and sleep quality and that higher stress levels led to lower sleep quality (Kang et al., 2018).
The results of this study empirically confirmed that urban gardening has an effect on improving sleep quality by promoting physical activity and reducing stress in middle-aged women. These findings will be helpful in developing and applying urban gardening programs to improve the sleep quality of middle-aged women in the future. However, since this study was conducted in a relatively short period of time with limited sample size, further research is necessary to verify the health promotion effects of long-term urban gardening programs across various regions.
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