Longitudinal Healthcare Utilization and Costs in Parkinson’s Disease: Pre-Diagnosis to 9 Years After

INTRODUCTION

Neurological disorders are the leading cause of disability, and amongst them Parkinson’s disease (PD) is growing at the fastest rate. There are presently 6.2 million individuals living with the disease, with the number projected to grow to 12.9 million by 2040 [1]. PD is a neuro-degenerative disorder that is associated with increased age. Thus, it can be reasonably postulated that global prevalence will increase with an aging population [2, 3]. The economic burden of PD is expected to grow exponentially due to the chronic and progressive nature of the disease with the development of motor and non-motor complications [4–10] as well as the increasing prevalence.

At present, there are few studies that explore long-term cost of illness in PD and fewer yet that combine both clinical and administrative databases [9–15]. The key limitations of existing studies are short duration of follow-up, recall bias associated with patient-reported costs, small sample sizes, and cross-sectional designs that do not allow the analysis of utilization and costs trends with disease progression [5–7, 15–20]. We therefore undertook this study to examine and compare longitudinal patterns of healthcare utilization and cost amongst newly diagnosed PD patients managed by movement disorder specialists and those without the disease, and to 1) estimate the incremental cost of care in PD patients and 2) determine the main domain drivers of healthcare cost, to inform future policy and fiscal planning for the long-term care of PD.

METHODS

RESULTS

Time trends in healthcare costs

Total healthcare cost

Mean total annualized healthcare cost was consistently higher amongst PD patients compared to controls through years 1–9 post-diagnosis (Fig. 1). The increase in cost was observed 2 years before diagnosis (SGD3102 vs. 2742; p < 0.001).

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Fig. 1

Average annual cost, total. Wilcoxon signed-rank test is performed to compare total annual healthcare cost incurred by PD patients and matched controls respectively. All differences are significant at p < 0.05. Each bar represents 95% confidence interval.

Domain specific healthcare cost

Mean annualized cost was higher amongst PD patients across all healthcare domains, except for primary care (Fig. 2). Costs of ED visits, hospitalizations, SOC, and ILTC increased steadily over 11 years in both PD patients and controls. Notably, the cost of specialist care amongst PD patients increased sharply by 91.4% between the years immediately before and after diagnosis, from SGD587 one year prior to index date to SGD1124 one year after index date. After the index date, PD patients incurred almost double the cost of specialist care compared to controls yearly (Fig. 2d).

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Fig. 2

Average annual cost, by healthcare domains. Wilcoxon signed-rank test is performed to compare annual cost incurred by PD patients and matched controls respectively in each healthcare domain. All differences are significant at p < 0.05 except for years indicated with an asterisk (*). Each bar represents 95% confidence interval.

Primary care cost for patients with PD increased from SGD284.78 at 2 years prior to index date to SGD399 at 3 years after index date, after which it decreased steadily at an average rate of 7.81% per year to SGD249 at year 9. In contrast, primary care cost for controls increased from SGD224 at 2 years prior to index date to SGD409 at year 9.

Cost attributable to Parkinson’s disease

The cost attributable to PD increased from SGD360 at 2 years prior to index date to SGD2477 in the first year of diagnosis to SGD3543 at year 9 (Fig. 3). Costs of ILTC, hospitalizations, and specialist care account for majority of the incremental cost, with each domain contributing an average of 41.7%, 29.9%, and 25.9% respectively to the total attributable cost per year, post index date.

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Fig. 3

Cost attributable to Parkinson’s Disease.

DISCUSSION

This study evaluated the longitudinal cost of care in PD patients managed by movement disorder specialists by determining the incremental healthcare utilization and cost incurred by PD patients compared with controls matched on age, sex, race, and comorbidities. It adopted a net cost approach to take into consideration all medical costs that made be directly or indirectly associated with PD. The average annual utilization rates and costs incurred by PD patients post-diagnosis, compared to controls, were higher across all healthcare domains except primary care. Attributable cost to PD rose from SGD2477 (USD1854) to SGD3543 (USD2652) over 9 years after diagnosis. Higher costs were observed up to 2 years prior to PD diagnosis (SGD3102 vs. 2742; USD2322 vs. 2052).

While this cost difference was also observed in the United Kingdom (£3021 in 2013 costs) [15] and the United States (USD5362 in 2013 costs) [32] in similarly designed studies looking at direct medical costs, the absolute cost difference and percentage increase in PD patients found in this study are significantly lower. A cross-sectional study conducted in Singapore also found that the mean annual total cost of PD (direct and indirect costs) was much lower in Singapore (USD10,129 in 2008 costs), compared with other developed Western countries [20]. A more recent study of elderly Medicare beneficiaries with PD reported primary PD-related costs of USD3429 (adjusted to 2018 costs), but almost half the cohort was ≥80 years (compared to our patients’ mean age of 66.2 years) [33]. Age is a well-established predictor of cost-of-illness in PD [9, 33]. Aside from differences in study methodologies, these discrepancies in costs are likely to be accounted for by differences in healthcare financing, cost structure, as well as efficacy and efficiency of the healthcare system [20, 34].

Additionally, approaches to pharmacological and non-pharmacological treatment of PD patients also differ according to region. The relative lower cost of healthcare amongst PD patients in Singapore compared to their Western counterparts may be in part due to lower utilization of dopamine replacement therapy, measured in levodopa equivalent daily dose. In a study of pharmacological treatment in a newly diagnosed cohort of PD patients from our center, we reported mean (SD) LEDD of 204 (113) [35]. Another center in Singapore reported LEDD of 352.45 (305.36) in patients with average duration of disease of 5.80 years [36]. Overall, these levels are lower than those reported in Western countries [36–38]. The cost discrepancy may also be attributed to lower rates of advanced surgical treatment in Singapore compared to other developed Western countries. From 2007 to 2017, our center performed deep brain stimulation (DBS) on 67 patients (out of 3556 patients), resulting in a utilization rate of 1.88%. A similar rate of 1.8% was also reported in another cohort of PD patients in Singapore [35]. This is lower than the average of 5–10% in other high-income countries [39]. Not taking into consideration the difference in cost of DBS across the various high-income countries, the lower utilization of DBS in Singapore may contribute to the lower average cost of healthcare for PD patients. However, this will not account for differences that are already apparent in the initial years of disease when patients are not yet DBS candidates.

Our study demonstrated an increase in healthcare utilization and cost even before the diagnosis of PD, with significant differences in primary care (3.5 (6.1) vs. 2.6 (4.0)) and specialist care events (2.4 (3.8) vs. 1.7 (3.2)) and costs at 2 years pre-index date. This was not observed in 2 previous studies where direct medical costs did not differ between PD patients and controls in a year just before diagnosis [32, 41]. The majority of our patients (82.6%) had early-stage disease (HY stage ≤2) at diagnosis. While the results could be confounded by the minority of patients who already had more advanced disease at diagnosis, a better explanation is the phenomenon of prodromal PD. Subtle motor and non-motor symptoms have been reported in PD patients up to 10 years prior to PD diagnosis. In particular, balance impairment, hypotension, urinary dysfunction, dizziness, depression, and fatigue have been recorded up to 5 years pre-diagnosis while constipation and tremor were observed at higher incidence rates up to 10 years pre-diagnosis [42]. This increased attendance of PD patients at primary and specialist care facilities affords clinicians the opportunity of conducting screening in a suitable clinical setting so as to identify patients with prodromal PD symptoms and allow for timely intervention or clinical trials. The recently updated Movement Disorder Society web-based prodromal PD risk calculator can further facilitate the identification of this group of patients who will need closer monitoring [43].

PD patients utilized more healthcare resources across all domains except primary care and incurred more costs correspondingly, compared to matched controls. The sharp increase in specialist care utilization and cost in the immediate year post-diagnosis can be attributed to the cost of investigations and active management of PD. This is contrasted with the time trend of primary care cost in our PD patients, showing that cost fell steadily from year 3 to year 9 post-diagnosis. This model of PD care in Singapore, in which there is a transfer of care from the primary care setting to specialist care at the point of diagnosis is in keeping with the American Academy of Neurology’s quality measures recommendations that neurology care should be available throughout the course of illness [44]. While previous studies have shown that neurologist care in PD is associated with fewer hospitalizations and acute care utilization, the jury is still out on its cost-effectiveness [45, 46].

Hospitalizations were the costliest events for PD patients and controls alike, contributing the most to total healthcare costs annually. The greatest domain driver of incremental cost when comparing PD patients to controls was ILTC, with PD patients using almost 3-fold the services and incurring a similar increase in cost. ILTC services comprise home-based (medical and nursing, meal delivery, personal care, and transport), center-based (rehabilitation, day care, and hospice care), and residential services (community hospitals and nursing homes). As PD patients are frequent users of these services, ILTC may be an appropriate setting to proactively screen them for potential disease complications and intervene to prevent costly hospitalizations. As observed in our study, PD patients encountered healthcare providers in ILTC settings more often than their specialist care providers (7.1 vs. 5.3 events/year). Thus, it is crucial that healthcare providers in the community are equipped to care for PD patients, to ensure continuity and completeness of their disease management. This may call for a multifaceted approach of restructuring of healthcare delivery systems (including fiscal policies), continuing medical education, training community-based healthcare professionals, and developing evidence-based guidelines [47, 48].

To our knowledge, this study is the first that takes a longitudinal view of cost-of-illness with a relatively large sample size and that combines objective administrative cost data with clinical information. A chief advantage of our study is the completeness of our direct medical cost estimates as the national MOH administrative covers at least 95% of citizens and permanent residents and captures long-term care costs, including institutionalization costs. The longitudinal nature of our data allows a better understanding of patterns and heterogeneity in healthcare utilization and costs over the natural history of PD, to facilitate intervention and policy planning. The diagnosis of PD in our cohort is robust as all patients were diagnosed and managed by a movement disorder specialist.

There are some limitations in this study. Firstly, this study did not take into account indirect costs in the form of informal caregiving or productivity losses. Thus, it is likely to underestimate true societal cost of disease as previous studies [8, 19] have shown that direct medical costs only account for 30–35% of total cost-of-illness. However, it was not the aim of our study to capture all cost-of-illness, but rather to identify patterns that can translate into areas for improvement in care and ultimately, reduction of cost to patients and the healthcare system. Drawing data from administrative databases ensures high fidelity and reduces recall bias inherent to financial burden questionnaires often used to capture indirect cost data. Secondly, the MOH database may underrepresent primary care utilization. Primary care in Singapore chiefly comprises polyclinics (public primary care institutions) and private GP clinics. While all polyclinics were captured in the database, only GP clinics participating in the national Community Health Assist Scheme were captured, resulting in a coverage of approximately 62% of all GP clinics. In addition, PD cases were drawn from the database of a tertiary healthcare institution where patients receive specialist care. The cost of specialist care may hence be overestimated amongst cases. Thirdly, we did not have information on yearly LEDD or utilization rates of advanced surgical therapies in our particular cohort of PD patients, to provide possible explanation for differences in direct healthcare costs in comparison to other high-income Western countries. Lastly, we did not take into consideration the impact of comorbidities or frailty on cost of healthcare amongst PD patients; indeed, we controlled for comorbidities by matching cases and controls on modified CCI score to approximate overall PD-specific disease burden. Frailty is increasingly recognized as an important factor for health outcomes in PD and future observational study analyses will have to adjust for it. [49]

This study has yielded new information on the incremental cost of care in PD and identified domains that drive this expenditure. These identified patterns can potentially inform efforts to improve PD care and reduce its economic burden, through suitable screening modalities, early medical intervention, and ancillary care to stymie disease progression and development of complications.