Healthy life expectancy (HLE) is the expected number of years to live in good health, excluding periods of illness or injury [1]. Statistics Korea published the HLE estimate for people born in 2018 for the first time [2]. HLE also includes a dimension of quality of life based on the length of time a person expects to maintain a healthy lifestyle [1]. In Korea, the average life expectancy of women born in 2018 is 85.7 years, and that of women born in 2030 is 90.8 years [2], which exceeds 90 years of age for the first time in world history [3]. Given that the average HLE for women born in 2018 is only 64.9 years, women born in 2018 will live with disease and disability for about 21 years [2]. Women live on average 6 years longer than men, but HLE is estimated to be 0.9 years longer [2]. Therefore, since women may have worse health from around the age of 65 than before, more active health management is needed from middle age onwards.

Health-related quality of life (HRQoL) is a broad concept that includes physical, mental, emotional, and social functioning [4]. Many studies have reported the following factors affecting HRQoL in middle-aged women. General characteristics such as age, economic status, and level of education [5]; physiological factors such as obesity, menopausal conditions, and comorbidities [5]; psychological factors such as perceived health status, stress [6], and depression [7]; social factors such as social support and occupation [8,9].

Menopause is a spontaneous, unavoidable event that every woman will experience. Therefore menopause is considered the most crucial factor in the well-being of middle-aged women [5,7]. During the menopausal period, women experience menopausal symptoms such as hot flushes, night sweats, sleep problems, chilling, mood changes, vaginal dryness, and arthralgia [5]. The menopause stage is classified by the STRAW (Stages of Reproductive Aging Workshop) staging system, widely considered the standard for menopause [10]. According to STRAW, the late menopausal transition (MT) occurs when an intermenstrual interval equal to or greater than two skipped cycles or more than 60 days. Early postmenopause is 5 years after the final menstrual period. A prospective, longitudinal study in Korea with 2,204 women aged between 44 to 56 years old reported that women in late MT and postmenopause have more severe menopausal symptoms than the other stages of menopause [5]. Therefore, menopausal symptoms may affect HRQoL of women during the late MT and early postmenopause.

Symptom management is paramount in nursing practice and emerges as an essential focus of nursing science [11]. Nurses can provide symptom-focused care, including measuring symptoms, assessing factors that affect symptoms, preventing worsening of symptoms, and managing to alleviate symptoms [12]. Symptoms are the central focus of the theory of unpleasant symptoms (TOUS), a mid-range theory developed by Lenz et al. [11]. TOUS consists of three main concepts; antecedent factors, symptoms, and performance. Physiological, psychological, and situational factors are antecedent factors that directly and indirectly influence performance, and symptoms are proposed to mediate this relationship [12].

Late MT and early postmenopausal women experience more severe menopausal symptoms, which can change their HRQoL [5]. Therefore, this study aims to explain HRQoL of Late MT and early postmenopausal women by applying TOUS, focusing on menopausal symptoms. This study may provide practical implications for developing strategies and interventions to improve Korean women’s HRQoL.

Based on the TOUS, this study aimed to examine the effect of perceived health status, psychological distress, social support, and menopausal symptoms on HRQoL and the mediating effects of menopausal symptoms in Korean women during the late MT and early postmenopause. The specific objectives are as follows: (1) to investigate the differences in HRQoL by general characteristics and health-related characteristics; (2) to examine the levels of perceived health status, psychological distress, social support, menopausal symptoms, and HRQoL and to analyze the correlation between these variables; (3) to investigate the direct effect of antecedent factors on HRQoL and indirect effects through menopausal symptoms; and (4) to test the statistical significance of indirect effects of menopausal symptoms.

This study investigated the effect of antecedent factors (perceived health status, psychological distress, and social support) and symptoms (menopausal symptoms) on performance (HRQoL) based on TOUS. The mediating effect of menopausal symptoms on the relationship between antecedent factors and performance was also investigated.

This study found a significant difference in HRQoL according to the comorbidities. It was consistent with previous studies in which those with fewer comorbidities had a higher HRQoL [7] and those who had no comorbidity had higher HRQoL [8]. Discomfort or stress caused by comorbidity may affect the low HRQoL. Nurses need to assess the presence of comorbidities to improve the HRQoL. The average HRQoL score in this study (131.17) was lower than the women aged 40 to 60 years in the study of Jung and Chun [9]. It might be because the proportion of respondents with comorbidities in this study was higher (40.1%) than in Jung and Chun’s study (25.9%). On the other hand, this score is higher than the HRQoL score reported for older Korean women living alone [23]. These results may be due to the presence of spouse and age as some studies reported that quality of life was lower among those with no partner [8,23] and older age [5,8,23].

As proposed by the TOUS, this study supported that antecedent factors had a significant effect on performance; perceived health status, psychological distress, and social support showed significant direct effects on HRQoL. Perceived health status having a direct relationship with HRQoL support a previous study that showed perceived health status strongly affected HRQoL in middle-aged women [6]. The average score of perceived health status was 9.34, slightly lower than a previous study [24]. These results appear to be due to differences in comorbidities. In the previous [24] and this study, 21.0% and 40.1% of respondents, respectively, had comorbidity. Perceived health status is closely related to objective health status and personal attitudes for evaluating health status [8]. People who perceive their health status positively tend to invest more time and effort in maintaining health-promoting behaviors [25]. Therefore, it is necessary to efforts to help women with reduced health awareness after menopause positively perceive their health status.

Psychological distress also had a direct relationship with HRQoL. Similarly, Sohn [7] and Jung and Chun [9] reported that psychological distress lowered the quality of life in middle-aged Korean women. Some studies have shown that when the brain continues to perceive stress or anxiety, it activates the body’s inflammatory response and promotes the release of cytokines [26]. Stress and anxiety also inhibit hypothalamic function, leading to fatigue, lethargy, depression, and cognitive dysfunction. Prolonged stress can have severe physical and mental health consequences, such as increasing the risk of premature aging, cytokine-induced disease, high blood pressure, angina, ischemic heart disease, and cerebral hemorrhage [27]. In addition, severe depression causes a loss of motivation and appetite, insomnia, and lethargy to decrease the quality of health [5,7]. Park and Choi [28] conducted an intensive mindfulness-based stress reduction program (8 times a week for 2.5 hours/week) for women between the ages of 40 and 59 years and found that the experimental group had significantly lower levels of stress, depression, and anger than the control group. Mindfulness meditation may be valuable as an effective mental training method that can reduce psychological distress in postmenopausal women. In this sample, 9.9% of respondents had a severe level of depression and 5.3% had a severe level of stress, which is comparable to other reports [9,24]. In contrast, 42.1% of respondents had a severe level of anxiety, but direct comparison with prior studies due to few studies using the DASS-21 in Korean women during menopause.

Social support had a direct relationship with HRQoL. The strong association between social support and menopause-related quality of life in previous research [7] supports the results of this study. This study’s average social support score was lower than a prior study [24], which may be due to age differences; i.e., the average age of respondents in this study was 54 years old, which is higher than the 47 years in the study of Jung and Oh [24]. The risk of social isolation increases as the elderly are more likely to experience stressful life events such as losing family or friends and chronic illness [7,24]. On the other hand, studies suggest that people who help others are less stressed and happier and experience positive emotions [29], also echoed in a study that middle-aged Korean women who volunteer are healthier than those who do not [30]. As such, middle-aged women entering MT can be encouraged to participate in various volunteer activities with this new perspective.

As proposed by the TOUS, this study also found that perceived health status, psychological distress, and social support had significant indirect effect on HRQoL that was mediated by menopausal symptoms, suggesting that postmenopausal women can increase HRQoL through management of menopause symptoms.

Respondents in this study were noted to have severe menopausal symptoms with an average of 22.29 points, which was higher than those of previous studies involving postmenopausal women [31], or MT and postmenopausal women [32]. These previous studies, however, did not divide postmenopausal into early or late stages. In contrast, this study only included women in the late MT and early postmenopause, i.e., groups who may be more likely to experienced greater menopausal symptoms. Therefore, this requires consideration in interpretation of findings.

If middle-aged women do not manage menopausal symptoms, the risk of chronic diseases, depression, stress, osteoporosis, and metabolic syndrome increases, increasing the overall socioeconomic burden. According to the Korean National Health Insurance [33], the cost related to menopausal disorders is rising every year from about 33.8 billion Korean won (approximately 26 million US dollars) in 2016 to approximately 53.2 billion Korean won (approximately 41 million US dollars) in 2020. This suggests that menopausal symptoms are more than an individual problem but are a significant public health issue.

In general, pharmacological and nonpharmacological therapies have been used to relieve menopausal symptoms. Menopausal hormone therapy (MHT) represents the most common treatment for symptoms of menopause [34]. MHT relieves genitourinary syndrome such as vulvovaginal atrophy, pain with intercourse, urinary incontinence, and vasomotor symptoms such as hot flushes and night sweats [5,34]. MHT can rehabilitate sexual function and marital intimacy and reduce the psychological distress of middle-aged women [35]. Thus, in middle-aged women who receive MHT, the perception of menopause and aging will be more positive than others, with lower levels of conflict within their social networks. However, controversy continues for the advantages and disadvantages of MHT. A study [36] in Malay, Indian, and China found that women using MHT had worse mobility, pain/discomfort, and anxiety/depression, respectively, compared to non- MHT users. Therefore, women who desire MHT should consider their preference, circumstance, age at initiation, menopause age, and treatment goal.

Several studies have shown the effects of natural ways to reduce the symptoms of menopause. Examples include a 16-week exercise program that improved bone mineral density and health-related fitness [37], a 15-week weight training program that reduced menopausal symptoms by half [38], and horticultural therapy for 12 sessions (twice a week) reducing menopausal symptoms [39]. Another study aimed at eliminating negative emotional and physical symptoms had a significant positive effect on menopausal symptoms and quality of life in middle-aged women [40]. Nurses could suggest effective nonpharmacological interventions to help women reluctant to take drug therapy such as MHT.

This study adds empirical support for the TOUS. A prior study applying TOUS for colon cancer patients reported symptoms from illness and surgery negatively correlated with a physical component score and a mental component score for quality of life [41]. Another using TOUS for chronic insomnia found that perceived stress, presleep arousal, and social support influenced insomnia; while insomnia affected functional health [42]. In this study, menopausal symptoms mediated HRQoL in women during MT and early postmenopausal stage during which women may experience menopausal symptoms. The findings of these studies provide support for TOUS propositions that symptoms can mediate the link between influencing factors and performance [12]. Therefore, interventions not only for perceived health status, social support, and psychological distress; but also for menopausal symptoms are very important to improve HRQoL in middle-aged women.

Although previous studies have focused on menopausal symptoms, to our knowledge, none have examined menopausal symptoms as mediating factors in the relationship between antecedent factors and HRQoL. Instead, they commonly examined menopausal symptoms as an independent variable [7,31]. Further research studies will benefit menopausal women if including menopausal symptoms as mediating factors to fully explain HRQoL in middle-aged women.

A limitation of this study is that respondents were a convenience sample of women in late MT or early postmenopause. Therefore, study findings should be applied with caution to women in other menopausal phases. Another limitation is that researchers collected data during the period when coronavirus disease 2019 (COVID-19) spread rapidly nationwide. The COVID-19 pandemic has been a traumatic event, creating significant prolonged stress for people in every aspect of their lives such as increased stress related to work, financial matters, lowered income, and lost jobs [43]. This context might have influenced their psychological distress and social support.

Despite these limitations, this study showed that menopausal symptoms partially mediated the relationship between perceived health status, psychological distress, social support, and HRQoL in late MT and early postmenopausal women and validated the TOUS theory for use in better understanding HRQoL in middle-aged women.

In conclusion, the conceptual framework of Lenz et al. [11] about TOUS provides a better understanding to improve the HRQoL of menopausal women such as a more concrete awareness of the complexity of performance and preventive and management strategies. More variables related to physical, psychological, and situational factors affecting the quality of life of postmenopausal women need to be explored in future studies and TOUS can be a helpful framework. While nurses need to focus on relieving menopausal symptoms providing integrated interventions that encompass a variety of antecedent factors and menopausal symptoms to improve the quality of life of women during late MT and early menopause stages, may require a multidisciplinary team approach.