1. Background

Tuberculosis (TB) still remains one of the most dangerous infectious diseases worldwide, although the World Health Organization (WHO) has strengthened the management of this disease since 1993 [1]. Most countries have been managing TB patients by establishing a national-level TB control plan, and Korea has also been implementing a national TB control plan with the goal of reducing the TB incidence rate to less than 10 persons per 100,000 population by 2030 [2]. However, in Korea, the number of new cases of TB reported in 2020 is 49.4 per 100,000 population, and TB is the disease with the highest incidence rate among legal infectious diseases. In addition, both the incidence rate of TB and the incidence rate of multidrugresistant TB (MDR-TB) are highest in Korea among OECD member countries [1, 2]. Therefore, there is an urgent need for the active management of TB in Korea.

With respect to TB treatment, most TB patients can be cured if a proper combination of first-line drugs is prescribed and the patient takes the drugs consistently for at least 6 months [3]. However, because most TB patients are no longer contagious and have an improvement in their symptoms to some extent only after two weeks of anti-TB drug treatment, some patients do not take medications regularly or discontinue drug treatment too soon [2]. In these cases, Mycobacterium tuberculosis proliferates again, leading to treatment failure, and the disease is likely to progress to drug-resistant TB [3]. If TB becomes drug-resistant, the cure rate becomes significantly lower than that of normal tuberculosis, the treatment discontinuation rate is increased due to the extension of the treatment duration, and the burden of social and economic costs is also increased due to the use of expensive second-line anti-TB drugs [2]. Therefore, it is important for TB patients to take anti-TB drugs steadily for a set period of time [3], and TB patients need to have the self-care ability to manage their disease for themselves for the treatment period.

Self-care is individuals' act of performing their daily activities for themselves to maintain and promote their life, health, and well-being [4]. If patients' needs of self-care are greater than their self-care ability, this leads to a lack of self-care, and the role of nursing is important in such cases [5]. According to previous studies, in patients with chronic diseases, self-care is an important factor in the disease treatment process [6, 7], and TB patients with a higher self-care ability are more likely to have an improvement in their symptoms and maintain a healthy life [8]. In view of these findings of previous studies, TB patients need to be equipped with the self-care ability because they need to receive drug treatment continuously until they are cured completely.

TB patients frequently experience social isolation for a long period, unemployment, avoidance or shunning by people around them [9], and some TB patients experience physical symptoms due to the side effects of anti-TB drugs, such as gastrointestinal intolerance and skin reactions [3]. Since these negative effects can act as causes of depression [10], a previous study found that TB patients are vulnerable to depression, and the prevalence of depression in TB patients is more than 50% [11]. In addition, a prior study reported that the likelihood of non-compliance with recommended medical treatment was 3.03 times higher in depressed patients than in non-depressed patients [12]. Moreover, depression has been shown to have negative effects on self-care. In particular, depression reduces the patient's interest in the diseases or motivation for treatment and decreases patient compliance with drug treatment [13, 14]. Therefore, it is necessary to assess the degree of depression in tuberculosis patients and examine how depression influences self-care.

Since TB patients tend to be neglected by people around them because of long-term drug treatment due to the nature of the disease or tend to be avoided by those around them due to the infectiousness of TB, it is important to provide them with social support through interactions with their families or people around them and medical staff's provision of information on treatment [15]. The social support for TB patients can be largely divided into medical staff support and family support. In this case, medical staff support refers to the positive support that physicians and nurses provide for the patient, and family support refers to the family members' supportive behaviors for the patient by which family members that are meaningful to the patient takes care of the patient and instills the patient with a sense of self-worth during the treatment process [16]. Social support has been found to positive influence self-care [16, 17, 18], and higher levels of social support have been shown to be associated with higher levels of self-care performance [17]. Therefore, since social support is an important influencing factor for self-care, it is important to investigate the level of social support among TB patients.

In recent previous studies on the self-care of TB patients, age [18], smoking [18, 19], religion [17], income [19], the experience of anti-tuberculosis drug discontinuation [18], knowledge [20, 21], health information literacy [21], stigma [18], stress [20], support system [17, 18], health belief [17], illness perception [19], self-efficacy [19, 22], and quality of life [22] have been reported as factors affecting self-care in previous researches. However, there have been few studies to investigate whether depression and social support are influencing factors for self-care among TB patients.

Therefore, this study attempted to investigate the relationship between depression, social support, and self-care and identify the factors influencing self-care in tuberculosis outpatients using a medical institution in order to present the basic data required for the development of intervention programs to improve the self-care ability of TB patients.

2. Purpose

This study aimed to investigate the levels of depression, social support, and self-care in TB patients, and determine whether depression and social support significantly influence self-care in TB patients. The specific objectives of this study are as follows:

1. Study Design

This study is a descriptive survey study to investigate the correlations among depression, social support and self-care among the tuberculosis outpatients of a medical institution, and identify factors affecting self-care among the participants.

2. Participants

The participants of this study were selected by convenient sampling among the patients aged 19 or older who were diagnosed with pulmonary and respiratory tuberculosis and were receiving anti-tuberculosis drug therapy in a tertiary hospital located in D city, and who were able to communicate in Korean and understand and respond to the items of the questionnaire. The sample size for this study was calculated using G*power 3.1.9 software. The minimum sample size for this study was determined to be 116 persons by positing a significance level of (α)=.05, a power of .90, and a medium effect size of .15 based on a previous study [19] as well as 5 independent variables. In consideration of the drop-out rate, questionnaires were distributed to 130 people. However, data from a total of 119 participants was finally used in the analysis, excluding 11 copies of questionnaires with incomplete or insufficient responses, so the sample size was satisfied.

3. Measures

4. Data Collection

The data of this study was collected from July 1 to October 21, 2018 after obtaining approval from the IRB of the relevant institution (IRB No: 2018-05-053). The researcher visited the outpatient department of a university hospital in D Metropolitan City, and explained the purpose and procedure of this study and the contents of the questionnaire to medical staff (physicians and nurses) to obtain the permission for conducting this study from medical staff and request for their cooperation. Thereafter, the researcher visited the outpatient clinic of the department of respiratory medicine of the hospital to recruit participants. A questionnaire survey was conducted with the participants who satisfied the inclusion criteria, fully understood the purpose and contents of this study, and voluntarily signed a written informed consent form. The time taken to complete the questionnaire was about 15 minutes. In addition, prior to the survey, the researcher explained to the participants that they could withdraw from the study at any time without any disadvantages, the collected data would be used only for the purpose of research, and the confidentiality of collected data would be maintained.

5. Statistical Analysis

The statistical analysis of the collected data was conducted using the SPSS/WIN 23.0 program. The specific methods of data analysis are as follows.

1. General Characteristics of Participants

Out of the participants, males accounted for 57%. The mean age of the participants was 57.82±17.18 years, and people aged 70 years and older accounted for the largest proportion (31.9%). Regarding educational level, the proportion of high-school graduates was 39.5%, and for marital status, 66.4% were married. As to the presence of cohabiting family members, 73% of the participants had one or more cohabitants. As for smoking status, the proportion of nonsmokers was 63%, and in terms of subjective socioeconomic status, people with middle subjective socioeconomic status took up the largest proportion (67.2%). Regarding the presence of other disease (s), 54.6% did not have other diseases. For treatment history of tuberculosis, 72.3% did not have previous treatment history of tuberculosis. The mean period of anti-tuberculosis drug therapy was 4.11±3.51 months, and the percentage of patients receiving anti-tuberculosis drug therapy for less than 3 months was 37.8%, accounting for the largest proportion. 54.6% of the participants had the experience of the side effects of anti-TB drugs, and 80.7% did not have the experience of drug discontinuation. Also, 94.1% did not have drug-resistant tuberculosis (Table 1).

Table 1 Difference of Self-care according to General Characteristics (N=119) Click for larger image

2. The Levels of Depression, Social Support, and Self-care among Participants

The mean score for depression among the participants was 7.30±6.39 out of 27 points. The mean score for social support was 3.86±0.87 out of 5 points, and regarding the subdomains of social support, the mean score for family support was 3.83±1.19 out of 5 points, and the mean score for medical staff support was 3.89±0.78 out of 5 points. The mean score for self-care was 3.46±0.53 out of 4 points. As to the subdomains of self-care, the scores for 'check-up and drug treatment', 'nutrition and health habits', 'outpatient visits', and 'resting sleep and activity' were 3.61±0.55 points, 3.45±0.55 points, 3.41±0.67 points, and 3.32±0.71 points, respectively (Table 2).

Table 2 Scores for Depression, Social Support, and Self-care (N=119) Click for larger image

3. The Level of Self-care according to the General Characteristics of Participants

With respect to the level of self-care according to the general characteristics of the participants, there was a statistically significant difference in the level of self-care according to subjective socioeconomic status (F=7.38, p=.001), drug discontinuation experience (t=-4.65, p<.001), and drug resistance (t=-2.09, p=.039). Regarding the level of self-care according to subjective socioeconomic status, a post-hoc analysis showed that the level of self-care was higher in the high subjective socioeconomic status group (3.61±0.41) and the middle subjective socioeconomic status group (3.55± 0.50) than in the low subjective socioeconomic status group (3.15±0.55) (Table 1).

4. The Correlation between Depression, Social Support, and Self-care among Participants

As a result of the analysis of the correlation between depression, social support, and self-care among the participants, self-care was found to have a significant negative correlation with depression (r=-.53, p<.001), while it was shown to have a significant positive correlation with social support (r=.68, p<.001) (Table 3).

Table 3 Correlations among Depression, Social Support, and Self-care (N=119) Click for larger image

5. Factors affecting Self-care among Participants

To identify factors affecting self-care among the participants, multiple regression analysis was conducted by entering variables found to be significantly related to self-care (subjective socioeconomic status, drug discontinuation experience, and drug resistance) among general characteristics as well as depression and social support as independent variables. Among these variables, subjective socioeconomic status, the experience of drug discontinuation, and drug resistance were treated as dummy variables in the analysis. In the multiple regression analysis, tolerance values were higher than 0.1, ranging from .87 to .97, and the variance inflation factor (VIF) was 1.20~1.33, not exceeding 10, the reference value. Thus, the problem of multicollinearity among independent variables was ruled out. Before analyzing the results of the multiple regression analysis, the Durbin-Watson test was conducted to detect autocorrelation in the residuals. As a result, the Durbin-Watson statistic was determined to be 1.94, a value close to the reference value of 2, indicating that there was no problem of autocorrelation, and the regression model was significant (F=49.06, p<.001).

In this study, factors influencing self-care of the participants were social support (β=.51, p<.001), depression (β=-.32, p<.001), the experience of drug discontinuation (β=-.30, p<.001), and drug resistance (β=-.14, p=.040) in descending order of the magnitude of their influence. Among the independent variables, social support (β=.51, p<.001) was found to be the strongest predictor for self-care in TB patients, and the explanatory power of the variables was 62% (Table 4).

Table 4 Factors Affecting Self-care of Tuberculosis Patients (N=119) Click for larger image