Heart transplantation (HTX) has become the definitive treatment influencing survival rates and quality of life in patients with end-stage heart failure (HF) [1, 2]. Worldwide, the median survival of adult heart-transplant recipients is 12 to 13 years and the 1-year survival rate is 91% [3]. During the last 30 years, advances in surgical techniques, perioperative management, and immunosuppressive therapies directed at acute graft rejection have improved life expectancy in heart-transplant recipients [3–5]. The improved prognosis has facilitated more attention to employment status post-HTX [2, 6, 7]. Employment is known to be essential for social identity, self-esteem, self-confidence, as well as mental and physical health in patients with HF [8, 9]. Moreover, labor market contribution carries economic advantages for both patients and society [8, 9].

Previous studies have reported a wide variation in the prevalence of return to work (31%–71%) in heart-transplant survivors [10–13]. Yet, studies on employment status after HTX have generally been based on questionnaires or other self-reported data. In Denmark, it is possible to make robust descriptions of labor market dynamics following HTX due to well-established and highly complete population-based registers and weekly longitudinal information on all public transfer payments from Danish authorities [14, 15]. A nationwide study in Denmark of patients with HF suggested that multimorbidity is associated with reduced chance of return to work within 1-year after first-time hospitalization [8]. Moreover, socioeconomic deprivation is known to be more likely in individuals with multimorbidity [16–19]. Improved insights into the influence of multimorbidity and socioeconomic position (SEP) on labor market participation in heart-transplant recipients may contribute to strategies to strengthen social recovery. Therefore, in this setting, we sought to describe 20-year trends in employment status for the Danish heart-transplant recipients, and examine the influence of multimorbidity and SEP.

A total of 649 heart-transplant recipients were identified during the study period. Of these, 492 were of working age (19–63 years) at the time of surgery, registered in the DREAM database and alive at discharge. The cohort contained 390 males (79%) and the median (IQR) age was 52 years (43–57 years). The three most prevalent non-psychiatric conditions before index-date in the HTX cohort were HF (87%) followed by cardiomyopathy (67%) and cardiac arrhythmias (48%). Psychiatric conditions were observed in less than 1% of recipients. The median (IQR) number of both non-psychiatric (excluding cardiovascular diseases) and psychiatric conditions was 1 (1-2) (Table 2).

Figure 1 displays the dynamic patterns in weekly changes in employment 1 year before and up to 2 years after HTX. The prevalence of regular employment 1 year before index date was 38%, decreasing to 12% at surgery, and increasing to 21% 2 years after index date. Recipients in a flexible job showed a stable pattern with approximately 6% having reduced health-related working capacity during the study period. The prevalence of heart-transplant recipients with health-related work absenteeism was highest at index date (35%), whereas the prevalence was 9% 2 years after surgery. Eight percent of the recipients were unemployed, not health related, 1 year before HTX versus 2% after 2 years. The prevalence of recipients on retirement increased the year up to HTX, while the prevalence was steady and approximately 50% 2 years after surgery. Four weeks before HTX, the prevalences were approximately: regular employment (18%); flexible job (6%); health-related work absenteeism (29%); unemployment, not health related (4%); retirement (43%).

Through the Sankey flow diagram in Figure 2, movements from 1 year before to 1 year after index date were observed between the groups of heart-transplant recipients in regular employment, with reduced work ability, or on retirement. Twenty-one percent of recipients with regular employment as well as 34% with reduced work ability moved to the retirement group. Within the group of recipients with regular employment, 27% moved to the group with reduced workability from 1 year before to 1 year after HTX. The movement from reduced work ability to regular employment was observed in 15% of the heart-transplant recipients.

Prevalence estimates of labor market participation within the group of recipients eligible for labor market participation at 1 year before HTX to 5 years after as well as prevalence by the stratified variables of multimorbidity and SEP are depicted in Figure 3. One year after HTX, 26% of the recipients participated in the labor market, increasing to 30% after 5 years (9% in a flexible job; 21% in a regular job). In the time between 2–5 years after index date, approximately 10% eligible for labor market participation did not participate on the labor market. Those recipients within the lowest age interval (19–40 years) compared to the highest age interval (51–63 years), presented higher prevalence with labor market participation (Figure 4). In recipients with at least two chronic diseases, the prevalence of both recipients eligible for and with labor market participation was lower compared with recipients with no more than one chronic disease (Figure 3). Of notice, we found no indication of differences in age between recipients with 0-1 versus 2+ chronic diseases (Supplementary Figure S1). We observed a socioeconomic influence in labor market participation. In heart-transplant recipients living alone, being single, with low educational level, or in the lowest income group, the prevalence of labor marked participation was lower during the study period, though less pronounced in recipients living alone (Figure 3). Except for educational level, the most socioeconomically disadvantaged heart-transplant recipients were younger (Supplementary Figure S1). Five years after HTX, characteristics of recipients with labor market participation were: living alone (27%) versus cohabitation (73%); single (35%) versus married (65%); low (36%) or medium-high (64%) educational level; low (13%) or medium-high (87%) income group.

Our nationwide study in heart-transplant recipients is the first to describe long-term employment dynamics with a high weekly accuracy. We had several novel findings: i) 5 years after HTX, 30% of the recipients participated on the labor market, 9% of those were in a flexible job; ii): sixty percent of survived recipients were retired as well as 10% of recipients eligible for labor market participation was unemployed 5 years after HTX; iii) recipients with multimorbidity had a higher age and a lower prevalence of employment; iv) socioeconomically disadvantaged heart-transplant recipients had a lower prevalence of labor market participation, despite being younger than the socioeconomically advantaged.

Previous studies have reported return to work following HTX [10–12, 29]. However, these studies did not describe detailed labor market participation by public transfer payments from authorities. White-Williams et al. performed [13] a questionnaire survey study in 237 heart-transplant recipients from the University Medical Centers in the United States (US). Pre-transplant (listed for HTX date), 17% of recipients were active on the labor market, increasing to 26% 1 year after surgery. Only, 45% of the recipients working 1-year post-transplant had also been working pre-transplant [13]. Kristen et al. (2009) [10] forwarded a questionnaire to 150 heart-transplant recipients 8.5 ± 0.4 years after surgery at a German university hospital. Thirty-six percent of recipients were of working age (<65 years) and employed after 12.6 ± 1.9 months [10]. A single-center study (2019) [11] included survived recipients attending a Scottish heart-transplant clinic (n = 154). One year before HTX, 61% (n = 47) of recipients were working. Of those, 83% (n = 39) returned to work and 21% had reduced working hours [11]. In the newly presented UNOS (United Network for Organ Sharing) database study, they addressed the prevalence of employment following HTX in the US [12]. The study included 10,132 recipients who survived at least 1-year (75% were males). Median (IQR) age in the non-working group was 51 years (42–56) versus 49 years (39–55 years) in the working group. Twenty-two percent of survived recipients were employed 1 year after surgery and employment prevalence of 2-year survivors increased to 32.9%. Within the group of recipients with employment 1-year after HTX, 62.8% were not working at listing or surgery date. Moreover, 16.1% who were not working at listing or surgery date obtained a working position afterwards [12]. Likewise, a newly published systematic review [30] on employment following thoracic transplantation reported that employment ranged from 19.7% to 69.4% for heart-transplant recipients [30]. The findings from the review and individual studies varied considerably. Discrepancies between these results may be explained by a variety of reasons, including inclusion criteria (e.g., working age interval; labor market participation status at index data), measures of labor market participation (e.g., questionnaire-based data; other self-reported data; question-asking technique at clinical visits), and national government set-up (e.g., universal public welfare benefits; other social services or more selective welfare stats).

Our register-based approach allowed us to illustrate the movements in labor market participation dynamically 1 year before and up to 5 years after HTX. Our findings confirm the results based on the UNOS database with higher accuracy and prolonged long-term follow-up. Thus, approximately 30% of the survived heart-transplant recipients were employed long-term after surgery (21% in a regular job as well as 9% in flexible job). Additionally, we observed that only 5% of recipients moved from reduced workability to regular employment within the first year after HTX and the prevalence of retired recipients increased from 35% to 60%. These observations support the idea that with vocational rehabilitation, many heart-transplant recipients are able to participate on the labor market [2]. However, as shown in our data, 10%–12% of the recipients eligible for work are unemployed in the period 2–5 years after HTX, which could reflect missed facilitation of social recovery.

Several factors have been identified to influence labor market participation. The UNOS database study [12] found that independent predictors of obtaining employment after HTX were age, gender, employment status at time of listing or transplant, education, insurance status, ethnicity, and postoperative complications. However, the most influential predictor was reported to be the preoperative employment status [12]. Similarly, the review regarding thoracic transplantation reported that the most positively associated factors with employment post-surgery were younger age, higher educational level, and pre-surgery employment, whereas the most negatively associated were longer duration of unemployment before transplant and Medicaid coverage [30]. Unlike these studies, we described the impact of multimorbidity and SEP on labor market participation. Our study showed that multimorbidity reduced both the prevalence of recipients eligible for labor market participation and the number of recipients with labor market participation during a period of 5 years after HTX. The Danish nationwide register-based cohort study [8] among first-time hospitalized patients with HF patients (n = 21,455) reported that comorbidities such as stroke (OR 0.55; 95% CI 0.45–0.69), chronic kidney disease (OR 0.46; 95% CI 0.36–0.59), and diabetes mellitus (OR 0.76; 95% CI 0.68–0.85) were all associated with a reduced likelihood of return to work [8]. Another Danish study [31] including 5,365 patients hospitalized with cardiac disease (mean [SD] age 50 years [11]; 70% males) reported that poor self-reported physical and mental health and high symptom burden were associated with detachment from the workforce within 1-year after discharge [31]. Along with our results, these studies support that heart-transplant recipients with the ability to work may have a better physical function, less limitation in their activities, lower age, and male gender.

Our results could indicate socioeconomic differences in workability following HTX. In accordance with the previous UNOS study [12], we found that in recipients with a lower level of education or income, the prevalence of both eligibility and participation on the labor market was lower. A possible explanation could be that individuals employed and having a low SEP are known to be more predisposed to unfavorable psychosocial working conditions and more likely face mental and social problems outside the workplace compared with those employed with a high SEP [32]. Thus, they might experience additional barriers to labor market participation. Accordingly, employment-related barriers for workability, such as less physically demanding jobs in individuals with a high educational level, is reported to facilitate more successful reintegration into the labor market [9, 12, 30, 32]. The slightly lower prevalence of both eligibility and labor market participation in heart-transplant recipients living alone or unmarried reflects that social support from a partner might result in improved self-management and physical recovery in heart-transplant recipients. This was supported by a recent Danish study [27] in heart-transplant recipients (n = 649; 78% males, 59% in age interval 41–60 years) suggesting a higher risk of first-time MACE (Major Adverse Cardiovascular Event) within 1–10 years after surgery (HR 1.46, 95% CI 0.98–2.17). In addition, the study illustrated that low educational level (adjusted HR 1.66, 95% CI 1.14–2.43) and low income (adjusted HR 1.81, 95% CI 1.02–3.22) were associated with a first-time MACE [27]. In agreement with our findings, these observations indicate a higher illness burden in socioeconomically disadvantaged heart-transplant recipients, thus leading to reduced workability.

In agreement with previous studies, our observations underline the call for more special attention to address employment status in the target group of socioeconomically disadvantaged heart-transplant recipients with multimorbidity. However, more research is needed into strategies to support workforce reintegration continuously and long-term after HTX. Systematic screening of heart-transplant recipients at follow-up visits for self-reported psychical, social, and mental factors associated with reduced labor market participation may be beneficial.

The major strengths is the use of nationwide administrative and clinical registries with complete and unselected information. These registries made it possible to present weekly, detailed and updated data on labor market participation with complete and long-term follow-up during 1994–2018. This strengths is essential compared to the UNOS-STAR database study (part of the International Society for Heart & Lung Transplantation), where employment status is documented by systematic questions at the time of post-transplant follow-up visits.

Our study also has some limitations. Given the reliance on the DREAM register, visibility into health-related disability payments was reduced to governmental expenses with no information pertaining to employer disability. Moreover, the first 2 weeks of any social transfer are not recorded in the DREAM register as the employer covers costs. This limits a complete understanding of labor market dynamics, but likely only for those who are disabled for a very short period, as those disabled for longer periods would typically receive governmental benefits. Consequently, this is unlikely to impact the study findings. Another limitation is that this study is observational and has a small sample size. We have a descriptive study design and as such, we could not assess any confounding effects. Thus, descriptions and illustrations may not be interpreted as associations or causations. Finally, the transferability of our findings may only be relevant to other European countries with a social structure and a public welfare system similar to Denmark.

Five years after HTX, 30% of recipients participated on the labor market, whereas 10% of recipients eligible for labor market participation were unemployed. Recipients with multimorbidity have a higher age and a lower prevalence of employment. Socioeconomically disadvantaged heart-transplant recipients displayed a lower prevalence of labor market participation, despite being younger compared with the socioeconomically advantaged.