People with a disability need comprehensive and consistent healthcare services because they often experience disability-related health problems in addition to common health conditions not associated with their disability [1] [2] [3]. Although they may have highly subjective clinical needs, their medical expenditure is consistently higher than that for people without a disability [4][5]. In a questionnaire related to outpatient treatment and hospitalization service, 45% (outpatient treatment) and 20% (hospitalization service) of people with a disability indicated they use healthcare services, but only 27% (outpatient treatment) and 9% (hospitalization service) of people without a disability had been using healthcare services. Households with people with a disability dedicate 20% of their income to medical expenses, although people without a disability only spend 3.4% of their income on these expenses, thus highlighting the burden of medical expenses on people with a disability [6]. In addition, these individuals may not be using available healthcare services due to disability-related limitations in educational, economic, social activities, or other direct or indirect barriers of access to hospitals [7] [8] [9] [10] [11] [12].

Economic activities of people with a disability are significant because their quality of life may be improved by increased income and by demonstrating their abilities through such activities. However, consistent employment for people with a disability can present many challenges. The employment rate of people with a disability from a 2011 survey in South Korea was only 35.5%, whereas the employment rate of people without a disability was nearly double at 60.3%. The major employment types of workers with a disability include jobs related to simple labor (30.1%), a craft (12.5%), or agriculture, forestry, or fisheries (12.2%), many of which provide a low income. In addition, 47.5% of all employees with disabilities worked in a place with four or fewer workers [13]. The results of this survey indicate that it is difficult for people with a disability to gain a high-income job, and they often cannot escape poverty-level conditions, even after employment.

Previous studies have focused on employment of people with a disability, especially on gaining employment [14][15][16], and many studies have been expanded to include various types of disabilities [17] [18] [19] or gender-related differences [20] [21] [22]. However, these studies often do not consider that the average work period of people with a disability is 67 months, and 44.8% of unemployed individuals with disabilities work for less than one year [23]. Although factors affecting catastrophic health expenditure (CHE) among elderly people with a disability have been investigated, no study has explored the impact of economic status changes on CHE among households with people with a disability in Korea. Therefore, we examined how the burden of medical expenses in these households varies according to changes in economic status. We also determined if a relationship exists between CHE and disability severity.

Data: This project utilized the panel survey of employment for the disabled (PSED) from 2010–2012. The PSED includes panel data from repeatedly measured households living with people with a disability and provides useful data for studying the economic activities of people with a disability related to their employment. The main data of the survey consists of demographic data (gender, age, education, disability status, disability grade), economic participation factors which utilize the questions and standards of the Korean National Statistical Office, and employed, unemployed, and non-economically active population factors. In addition the individual and environmental factors which influence economic activity are included. The PSED conducted 1:1 interview surveys with people with a disability directly. Since structure and contents of this data are more complex compared to cross-sectional data, this survey used CAPI (computer-assisted personal interviewing) method to minimize the problem. Interviewers input the response of interviewees in the computer installed CAPI and investigators were able to check logically wrong response using the method. The PSED only allowed the head of household or nearest guardian to reply if a direct response was impossible due to an intellectual disability or mental disorder. The substitute response rate was 7.2%.

Study Sample: We used a stratified cluster systematic method to select the sample of households used for this study. The survey was stratified by 15 metropolitan cities and provinces in South Korea, age (15~60, 61–75), and type of disability. The survey divided age to examine people under 60 years old because they are major target related to disability policy in South Korea. The sample size was calculated by proportional distribution using area and type of disability according to two age groups. The selected records included data from the 3rd wave (2010), 4th wave (2011), and 5th wave (2012) during the three-year research period, respectively. We excluded households that were dropped or added during this period and subsequently queried records from 4,065 households.

Dependent Variable: The dependent variable was CHE as defined by the World Health Organization (WHO). According to the WHO, CHE occurs when out-of-pocket (OOP) spending exceeds 40% of a household's capacity to pay, and this standard should be altered appropriately for each country [24]. We defined a household's capacity to pay as the amount of money spent per month, excluding food expenses [25]. An OOP expenditure is a payment made by a household when receiving a health service. Medical and drug costs resulting from emergency and outpatient care, as well as from hospitalizations, were included as OOP payments, whereas transportation and nursing costs were excluded. Thus, CHE was defined as health expenditures that were 40% greater than the ability of the household to pay.

Independent Variable: The main independent variable for this study was economic status change of people with a disability. We stratified households into four categories with respect to job status: employed-no change, employed-then-unemployed, unemployed-then-employed, or unemployed-no change.

Explanatory Variables: We used several covariates to analyze demographic and socioeconomic characteristics and health status. Demographic characteristics included sex, age, marital status, and socioeconomic factors such as education and income level. Income level was measured by summing the total family income, including the income from employment, assets, pensions, financial support from the government, and other sources. Household income was adjusted by taking the square root of the number of household members. As a proxy for health status, we used self-rated health, severity of disability, and chronic diseases to control for the participant's health condition and health behavior, which can affect health care utilization. In addition, we examined household characteristics, such as the number of senior citizens, total number of family members, and the number of employed individuals.

Statistical Analysis: The frequency with which CHE occurred overall after accounting for demographic, socioeconomic, and health status was determined by performing a chi-square test. To identify factors associated with CHE and, in particular, to examine the relationship between changes in economic status and CHE, we used the GLIMMIX procedure under the marginal model (population average model). The odds ratio (OR) was calculated through the regression coefficient gained through GLIMMIX procedure and presented with the 95% confidence interval (95% CI). We used the SAS 9.3 statistical package (Cary, NC, USA) for data analysis.

General characteristics of households analyzed in this study are given in Table 1. Among the 4,065 households with at least one person with a disability, 174 (4.3%) experienced CHE. At the individual level, elderly people had a higher proportion of CHE than younger individuals or those with a lower educational level. People with a disability with negative self-rated health or those with chronic diseases also experienced a higher frequency of CHE. We also observed a significant difference in the proportion of economic status changes and CHE. At the household level, households living with senior citizens were associated with a higher frequency of CHE, whereas households living with an employed, people with a disability experienced a lower frequency of CHE. We observed a significant difference between the number of family members in a household and the frequency of CHE. Interestingly, we observed no significant relationship between CHE and sex, marital status, severity of disability, or income level.

Table 2 presents the results for factors associated with CHE in South Korean households. People with a disability living alone had a higher risk of catastrophic medical costs than those living with a spouse. Households living with people with a disability who experienced changes in job status from employed to unemployed or who were unemployed with no change were more likely to incur CHE compared with households in which people with a disability continuously held a job. Households with more than two family members were also more likely to incur CHE.

Table 3 presents results for changes of economic status associated with CHE in households according to severity of disability. After adjusting for all variables used in Table 1, we saw no significant difference in CHE associated with changes in economic status for individuals with a highly severe disability. However, households with people with a disability who experienced changes in job status, either from employed to unemployed or from unemployed to employed, or were unemployed with no change were more likely to incur CHE compared with households in which people with a disability continuously held a job, even if he or she experienced a low-severity disability.

We identified the factors affecting catastrophic health expenditure as marital status, self-rated health, chronic diseases, and the number of senior citizens and total number of household members. The relationship between marital status and CHE has been differentially identified by several studies. For example, although some studies showed that people with a disability living with spouse had a higher risk of CHE than those living alone [26], research that examined CHE of low-income households yielded opposite results [27]. In our study, people with a disability living alone had a higher risk of CHE than those living with a spouse, which may imply that the ratio of medical expenses to total expenditure is higher in unmarried participants. In addition, households living with senior citizens or with more than two members were more likely to incur CHE, which supports similar previous studies involving people without a disability [28][29]. Thus, we need to consistently examine vulnerable groups, such as low-income households or people with a disability living alone, with respect to increased CHE.

Health-related factors affecting CHE in our study included self-rated health and chronic diseases, which is similar to the results of previous studies related to people without a disability [30][31] and people with a disability with chronic diseases [32] [33] [34]. If households include a person with chronic diseases, they would likely continually incur medical expenses that may be increased by payments not covered by health insurance.

Households in which people with a disability recently lost a job or were previously unemployed are more likely to incur CHE than households with people with a disability who had been consistently employed. Although no previous research linking CHE to changes in economic status of people with a disability has been performed, our results are similar to those of one study that investigated unmet healthcare needs following changes in economic status in people without a disability [35]. Further studies should explore this same relationship in people with a disability because CHE is commonly positively associated with unmet healthcare needs due to economic reasons [36].

We also examined if changes in economic status were associated with CHE in households according to severity of disability. Although economic status changes of people with a severe disability did not significantly affect CHE incidence, we found that households with people with a mild disability could still incur CHE. This phenomenon reflects the medical assistance policy for people with a disability in South Korea, which provides low-cost medical benefits to people with a severe disability. As a result, decreased income in this population due to economic status changes did not significantly relate to CHE. However, households with people with a mild disability not receiving these medical benefits did experience increased CHE, even after gaining employment. These results imply that we should consider healthcare access of people with a mild disability as a potential contributing factor to CHE.

This study has a few limitations. Firstly, it was difficult to determine levels of CHE for people without a disability because we analyzed households with people with a disability only. However, we did compare our results with those from previous studies related to people without a disability. Secondly, comparing our CHE results with previous studies is difficult because various criteria (10–40%) have been used as the threshold of CHE. Thus, we referred to previous studies that used a 40% threshold as recommended by the WHO. Thirdly, the actual prevalence of chronic conditions is likely higher than that reported in the PSED because some conditions may not have been diagnosed.

Despite these limitations, this project is significant because it is the first study to examine the impact of economic status changes on CHE among households with people with a disability in South Korea. We believe this study could be used as important evidence for expanding support for people with a mild disability because the Korean government has consistently increased medical support programs for people with a disability [37]. Second, this study's longitudinal design allows us to assess the stability and continuity of several attributes of a sample group by repeatedly observing the same participants. Another major strength of its longitudinal design is that cohort effects can be avoided because we examined one group of individuals over time, rather than comparing several different groups that represent different ages and generations.

Households with people with a disability who experienced changes in job status from employed to unemployed or were unemployed with no status change were more likely to incur catastrophic health expenditures (CHE) compared with households in which people with a disability was continuously employed. In addition, households with people with a mild disability were more likely to experience CHE than those with people with a severe disability who were supported by government-sponsored medical aid. Given the insecure employment status of people with a disability, people with a mild disability who have not received this medical aid are more likely to face barriers in obtaining needed health services. Our results indicate that change in economic status may be a more significant contributing factor to CHE than level of disability, thus highlighting the need to expand medical to people with a mild disability.

We would like to thank Manjusha Sala, BioScience Writers, who provided English translation services, as well as writing revision service. Also, this work was supported by a Korean Medical Association Grant funded by the Korean Government. The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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