Disparities in the medical expenditures of patients with cancer and concomitant mental disorder: analyzing the effects of diagnosis sequence order

Healthcare expenditures continue to grow at a fast pace around the world. U.S. National Health Expenditures grew5% annually from 2005 to 2017, and stands at 3.3 trillion dollars or 17.9% of GDP [1]. US health care spending increased 4.6 percent to reach $3.8 trillion in 2019, similar to the rate of growth of 4.7 percent in 2018. The share of the economy devoted to health care spending was 17.7 percent in 2019 compared with 17.6 percent in 2018 [2, 3]. Conditions in Taiwan are similar: national healthcare expenditures have increased at an average annual rate of 3.6% [4]. Meanwhile, NHI revenue has not kept pace with the growth in expenditures. In 2017, NHI expenses grew 5.5% while revenue only increased 0.5%, and in 2016 revenue actually fell 8.4% while expenses grew 5.6% [4]. Furthermore, over half of all major illness inpatient expenditures in Taiwan is spent for the treatment of just two diseases: cancer(46%) and mental disorder (MD) (11%) [4].

Cancer is the second leading cause of death, and is estimated to be responsible for 9.8 million deaths in 2018or 16.7% of all deaths worldwide [5]. In Taiwan, it ranks as the number 1 cause of mortality, where annual cancer deaths currently account for 28.2% of all deaths [6].The World Health Organization(WHO) also states “the number of new cases is expected to rise by about 70% over the next 2 decades”. Description of past research that individuals are likely to simultaneously suffer from both malignant neoplasms and mental illness. Psychiatric issues were found present in 20%, up to as much as 50%, of cancer patients [7‐10]. These study findings suggest that the prevalence of mental disorder among cancer cohorts is consistently much higher than in the general population. Mental disorders encompass different illnesses that are defined by the WHO as being characterized by “abnormal thoughts, perceptions, emotions, behavior and relationships with others.” The WHO also states that individuals with either depression or schizophrenia have a 40 to 60% higher chance of premature death as compared to the general population [5] caused by somatic illnesses such as cancer. In Taiwan, the prevalence of mental illness has risen from 8.8% just ten years ago to 11% in 2016 and is expected to continue to rise [6‐11].

The Organisation for Economic Co-operation and Development estimates that cancer, mental health, along with circulatory disease, account for over 40% of all hospital spending, and “cancer is the second most important disease group accounting for around 13% of hospital spending [12].The total annual economic cost of cancer was estimated to be US$ 1.16 trillion in the WHO’s Annual Cancer Report 2018 [5]. In Taiwan, the medical utilization of cancer occupies nearly 40% of all major illness insurance claims (Outpatient: 33.6%, Inpatient: 45.7%) [6]. The dual presence of both cancer and mental disorder in patients leads to increased more expenditures. Past research has shown a disparity in the monetary burden between cancer patients with poor mental health and those without. The increase can be as large as24% to over 50% [13‐15]. These large and adverse effects of comorbidity with mental disease merits further research involving cost analysis.

Cancer patients have been shown to be more likely to develop psychiatric disorders [16‐18], and the combined cost of cancer with concomitant mental disorder is not an additive equation, but an exponential one [19]. Due to the heavy weighting credited to cancer and mental illness in the profile of healthcare expenditures [4], it would be worthwhile to investigate the costs associated with these disorders [20‐23]. Despite the growing importance, there remains a lack of research looking at the intersection of cancer and psychiatric disorder. There has especially been scarce research dividing the comorbid cohort by sequence of diagnosis and conducting a directional analysis. This study attempts to close the knowledge gap in researching the effects of the temporal order of the onset of these two diseases on patient utilization. It’s also one of the first cost analysis studies involving these two important diseases with propensity score matching to pair the study cohort with a comparison cohort. With the depth of information available in the databases of the Taiwan Ministry of Health and Welfare, insights extracted could prove beneficial in enacting policies for resource reallocation, and potentially work toward reducing the economic burden on already strained national funds. Especially as healthcare delivery administrators try to strike a balance between patients’ prolonged survival, quality of life, and medical expenditures [24].

Our research is using National Health Insurance Research Database (NHIRD) from the Ministry of Health and Welfare (MOHW) Data Science Center 2005–2015, this retrospective matched-cohort study retrieves patients with cancer and/or mental disorder aged over 20 years. Target patients are divided into 3 groups based on diagnosis of either cancer or MD or both. All patients are then matched with a counterpart free of both cancer and MD, forming the comparison counterpart group. A second framework involving cancer patients with concomitant MD compares different diagnosis sequence order groups with cancer patients without MD.

The extracted case cohort included 321,045 patients that were diagnosed with either cancer, mental disorder, or both. The case cohort was matched with comparison counterparts for a total of 642,178 patients (Figure S1). Within the case cohort, 301,555 had mental disorder, 11,963 had cancer, and 7,527 had both. Further dividing by sequence order,2,498 patients were diagnosed with pre and post-cancer MD, 2,847 with pre-cancer MD, and 2,182post-cancer MD. Among cancer patients the prevalence of mental disorder was 39% (Table S1). In addition, the majority were female (55.3%) in the study samples. Approximately 24% was aged above 60 years old, and the largest age group was in the 40 to 49 years bracket (23.0%). Most were of married status (79%) and more than half did not attain an education of above high-school level (59%). Majority percentage of patients had premium-based salaries below NT$20,008 per month (63%), and fell within occupation category 1 (44%) living in either the Taipei or Central region (56% combined). Patients within urbanization levels 1 and 2 also combined for over 57% of all patients (Table 1).

The presence of MD had a diminishing effect on utilization. Cancer patients with MD had lower costs than those without concomitant MD. This was different from expectations and contrary to results of past research looking at dollar amounts in measuring patient utilization. However, the results of this study are supported by two papers, both reporting inadequate treatment in cancer patients with MD. Davis et al. (2022), in a study examines pancreatic cancer treatment compliance in patients with prodromal depression or anxiety found that patients with prodromal depression or anxiety were significantly less likely to receive chemotherapy [30]. A second paper focused on psychiatric illness patients on colorectal cancer treatments found that individuals with a severe psychiatric illness (SPI) history had significantly less likely to receive guideline recommended treatment than colorectal cancer (CRC) patients with no history of MD. Stage II and III CRC patients with SPI history were 2.15 times less likely (95% CI 1.07–4.33) to receive potentially curative surgical resection and 2.07 times less likely (95% CI 1.72–2.50) to receive adjuvant radiation or chemotherapy [31]. Unfortunately, the reasons behind the inadequacies of treatment of cancer patients with MD cannot be interpreted directly from claims data [32]. Nonetheless, these results could indicate the adverse situation of MD patients in Taiwan in experiencing potential barriers to healthcare (non-adherence, unwillingness to seek and comply with treatment or delays in care), or a dilution effect in the treatment of MD instead of patients’ major chronic disease. In addition, authors speculate the lowered utilization of cancer patients with psychiatric morbidity could also stem from the adverse behavioral effects caused by mental disorder. To have a deeper understanding of how mental disorder negatively impacts adherence, we turn to studies directly assessing correlates of mental disease with patient attitudes toward treatment. Past research revealed 3 major views held by patients associated with MD, which acted as barriers to healthcare; first inadequate information about treatment or misinterpretation of the treatment [33]; secondly, fears about treatment and its side-effects [34]; third, forgetting appointments [35, 36].

Cancer patients with a pre-existing MD had lower expenditures than those without any concomitant MD, while patients with MD onset post-cancer had higher expenditures. This difference in sequence order effect could be caused by the pre-existing mental distress affecting access to treatment in patients during the period immediately after cancer diagnosis, or simply a longer time period with MD in pre-cancer MD patients. Another recent paper on seniors with prostate cancer found that those with prior severe mental illness had lower likelihood of receiving treatment in the first year after diagnosis [37]. For example, the adjusted odds ratio of undergoing surgery was 0.66 (95% CI: 0.49–0.89) and receiving radiation concurrent with hormone therapy was 0.81 (95% CI: 0.67–0.98). Pre-existing mental distress has been found to profoundly affect both delay in treatment and access to treatment, thereby potentially caused the reduced expenditures in this type of patients of this study. Another research disclosed that despite the increased mortality from cancer in people with MD patients, this population receives less cancer screening compared with that of the general population [38]. On the other hand, the set of patients that developed mental disorders post-cancer were found to have higher average annual expenditures per capita than those without MD at any time. [39]The possible reason is that MD will reduce treatment compliance, this result is similar to the previous research, and it is believed that patients with SMI are prone to palliative care; it revealed that SMI patients are prone to palliative care [32]. This also explains why we found that patients in the Post-Cancer MD group were the highest risk to become HUs.

In addition, a research pointed that HU is the group that accounts for the majority of healthcare spending, even disclosed that < 1% of HU in the US account for 22% of US healthcare spending [40]. We found that the costs in "Free of Both" group began to increase after Q3, therefore, we further analyze the time cost trend of EOL. An earlier analysis of Taiwan NHI expenditures comparing EOL costs of various chronic illnesses ranked cancer second in terms of highest final year EOL costs for decedents, but it did not look at disease specific cost trends approaching the final quarters or months [20]. Instead, it analyzed changes in type of medical expense and found that final quarter costs of decedents were dominated by acute inpatient expenses for most chronic diseases. However, other studies focused on cancer patients showed that cancer end-of-life care usually involved palliative or hospice care (ORs ranging 1.79 to 6.88); lower likelihood of intensive care at EOL (ORs ranging 0.26–0.68); lower odds of chemotherapy near death (ORs 0.41, 0.57); lower odds of emergency department use and shorter length of hospital stay [41]. Another research also indicated that individuals with bipolar disorder were more likely to receive palliative care and less likely to receive high-intensity EOL care [42]. Conversely, "Free of both" group had more EOL costs because of progressively complex medical needs [43, 44].

Using a nationally representative database of the population of Taiwan, the study evaluated the expenditures of cancer patients with concomitant mental disorders, with focus on comparing the effects of differences in the sequence of disease onset. Contrary to expectations, the presence of mental disorder could have a diminishing effect on utilization, specifically if the onset of mental disorder was prior to cancer. Patients with post-cancer mental disorders and cancer patients without MD had the highest and second highest costs among groups, respectively. The additional expenditures of cancer patients later diagnosed with concomitant mental disorder may come from more office-visits for mental health care, and excess medication. [45, 46] Patients diagnosed with cancer and pre-existing mental illness had lower expenditures compared to those with only cancer, indicating possible barriers to care. A pre-existing mental disorder reduced expenditures in cancer patients, potentially due to barriers to uptake of treatment caused by psychiatric distress in the period immediately after cancer diagnosis. Those with pre-cancer MD had lower average expenditures, lowered risk of high utilization than patients with post-cancer MD. To the author’s best knowledge, this is the first study to analyze the effects of cancer and mental disorder diagnosis sequence differences on medical expenditure in Taiwan, and the first to distinguish pre & post-cancer, pre-cancer and post-cancer patient group differences in the same study population.