INTRODUCTION

Parkinson’s Disease (PD) is the second most common neurodegenerative disorder, currently affecting 6.1 million people worldwide (Bloem et al. 2021; GBD 2016 Parkinson's Disease Collaborators 2018). It is chronic and progressive in nature, characterised by combinations of multiple motor and non-motor symptoms. Patients in the initial stages of PD are usually managed in the outpatient setting. However, in due course of time, various complications and comorbidities associated with the disease progression may surface, necessitating hospitalisation (Kelly et al. 2016). It has also been shown that persons with Parkinson’s (PwP) have a significantly increased need for institutional care. The hospitalisation rates of PwP are 1.45 times higher than for age-matched controls (Paul et al. 2017). The cause of the admission may be directly related to the disease progression, indirectly related, which may reflect complications of the disease, or may not be related to the disease at all (Oguh & Videnovic 2012; Paul et al. 2017). However, it was reported that the majority of admissions for PwP were not directly related to the disease (Temlett & Thompson 2006).

It is estimated that there are 19,586 PD patients in Malaysia as of 2016 (GBD 2016 Parkinson's Disease Collaborators 2018). As life expectancy in Malaysia is reported to have increased from 77 years (female) and 72 years (male) in 2014 to 77.6 years (female) and 72.7 years (male) in 2018, the prevalence of people suffering from chronic illnesses and disabilities, including PD, is also expected to increase (Ministry of Health, Malaysia 2019). This situation will burden readily overcrowded government public hospitals, whose current bed occupancy rate (BOR) stands at 70.01% compared to 48.85% reported in 2011 (Ministry of Health, Malaysia 2019; Tahrani et al. 2012).

Besides being a factor that influences BOR, length of stay (LOS) is also an essential measure of hospital resource fulfilment (Freitas et al. 2012; Gates et al. 2018). Lesser LOS indirectly indicates the improved quality of treatment, including a decreased risk of infection and medication side effects (Baek et al. 2018). Meanwhile, an increase in inpatient days implies inefficient bed management, which consumes more hospital reserves (Ministry of Health, Malaysia 2019; Tahrani et al. 2012). The PwP were found to have 2.3 days longer acute hospital stays than non-PD patients (Oguh & Videnovic 2012). However, it was also found that PwP, who were admitted due to diagnoses which were not directly related to PD had three days longer LOS than PwP admitted due to PD, as revealed by a study in Punjab (Paul et al. 2017).

There is a paucity of information, especially in terms of hospital performance, despite many studies having been done pertaining to PD in Malaysia, as almost all of them focused on clinical aspects of PD (Azmin et al. 2014; Hooi et al. 2017). Thus, the aim of this study was to examine the primary diagnosis of patients admitted with a known diagnosis of PD between 2010 and 2020, and their LOS in a teaching hospital in Malaysia. Findings from this study will be beneficial, especially in regards to health planning and budgeting, as Malaysia slowly progresses into an ageing population.

MATERIALS AND METHODS

Study Design

This is a retrospective cross-sectional study done at Hospital Canselor Tuanku Muhriz (HCTM), one of the five teaching hospitals in Malaysia, utilising patients’ records from the hospital’s health information system, known as the Caring Hospital Enterprise System (CHEtS). The study has been approved by the Research Ethics Committee of the National University of Malaysia (UKM PPI/111/8/jep-2021-342). All admissions with a diagnosis of PD, either as primary or secondary, diagnosed between 1st January 2010 and 31st December 2020 were included in this study. Diagnoses of PD were identified by diagnosis code G20, based on the International Statistical Classification of Diseases and Related Health Problems, 10th Revision (ICD-10). Primary diagnosis can be defined as the diagnosis principally responsible for the episode of admitted patient care (Kelly et al. 2016). Meanwhile, other existing diseases which also require management during the hospital stay will be referred to as secondary diagnoses. Data on patients’ characteristics, including age and gender, as well as their admission and discharge date, were also extracted for each patient. Patients with incomplete data, secondary parkinsonism, and non-citizens were excluded from the study. We also excluded patients under 50 years of age to reduce the probability of coding error as Young Onset Parkinson Disease (YOPD) which is relatively rare (Low et al. 2015).

Patients were divided into two groups based on the final primary diagnosis given during the hospital admission. The first group was Group I, which was for PwP with a primary diagnosis of G20. In this study, we assumed that the patients in this group were admitted due to causes directly related to PD, such as motor complications and the side effects of anti-parkinsonian medication. The other group was Group II, which was for PwP admitted primarily due to other causes (non-G20). This may include diagnoses which are indirectly related to PD, such as aspiration pneumonia, urinary tract infection, electrolyte imbalance due to inadequate oral intake, falls, trauma, aspiration pneumonia and diagnoses which may not be related to PD at all, such as cerebrovascular accident and renal failure (Koay et al. 2018).

The outcome of the study was the number of PwP admissions from 2010 to 2020, PwP’s age and gender were analysed descriptively, according to Group I and II, and reported as a percentage and median. The PwP’s age was categorised dichotomously as below 65 years or 65 years and above as the prevalence of PD is found to be higher in people aged 65 years and above (Kelly et al. 2016).

Another outcome was the LOS, which is the number of days calculated from hospital admission to the date of hospital discharge, which was also analysed as a category or a continuous variable, depending on the type of analysis (Aubert et al. 2020). The average length of stay (ALOS) was calculated. As the LOS was highly skewed, we chose median rather than mean as the average as it is more robust and practical (Lee et al. 2003). The LOS was categorised into three groups based on the ALOS; (i) short LOS (SLOS); (ii) normal LOS (NLOS); and (iii) long LOS (LLOS) (International Centre for Casemix and Clinical Coding 2019). The SLOS was admission that was 1/3rd of the ALOS, while LLOS was the admission that their length was three times longer than the ALOS (International Centre for Casemix and Clinical Coding 2019). The NLOS lies in between.

The proportion of PwP in Groups I and II was determined in percentage. For the primary diagnosis of patients in Group II, the principal diagnosis was determined and reported as a single ICD-10 code. After that, bivariate analysis, indicate an association between type of primary diagnosis, LOS and the PwP’s characteristics by using the Chi-square test. The primary diagnosis (single ICD-10 code) was further combined with other codes that fall into similar ICD-10 chapters to predict the relationship between the primary diagnosis and the LOS. The LOS category was categorised into two; SLOS and NLOS were combined as a group, while LLOS was maintained as another group to allow for binary logistic regression. All statistical analyses were performed using SPSS version 27.0 for Windows (IBM Corp, Armonk, NY, US) and conducted at a 95% confidence interval, using a p-value of 0.05.

RESULTS

In total, 1587 patients’ data were included in the analyses. In Figure 1, the number of admissions involving PwP in the study duration was described. More than 100 admissions were consistently recorded for every year except for 2012, where only 92 PwP were hospitalised. Meanwhile, the highest number of admissions was seen in 2019, contributing to 13.9% of the total admissions. Throughout the 10 years, the number of PwP primarily admitted for non-G20 (Group II) diagnoses were consistently higher than those for G20 (Group I).

Table 1 showed the characteristics of the admitted PwP. Slightly more than half of the patients are male (54.4%), while more than two-thirds of them are more than 65 years old (76.3%). The median LOS for the population was six days. Only 10.6% of the percentages were in the SLOS and LLOS categories. The PwP with a primary diagnosis of G20 was observed in 10% of admissions, with a median LOS of four days (IQR 3-8). Meanwhile, the median LOS for PwP, primarily diagnosed as non-G20, was six days (IQR 4-10).

Table 2 summarised the top ten primary diagnoses in Group II, which contributed 44.0% of the total diagnosis. Various infections made up the top four diagnoses, led by unspecified pneumonia (J18.90) and aspiration pneumonia (J69.0) with 9.1% and 5.0%, respectively. Further combinations of single codes into ICD-10 chapters revealed 'Chapter X: Diseases of respiratory symptoms' as the disease category with the highest frequency (19.2%), followed by 'Chapter IX: Diseases of the Circulatory System' (13.4%) and 'Chapter XIX: Injury, poisoning and certain other consequences of external causes’ (7.3%).

In Table 3, it was shown that PwP admitted primarily for 'Chapter I: Certain infectious and parasitic diseases' had the longest median LOS (10.50 days), followed by 'Chapter XII: Diseases of the skin and subcutaneous tissue' with a median LOS of nine days. Only three chapters had shorter LOS compared to G20, which are 'Chapter VIII: Diseases of the ear and mastoid process', 'Chapter XVIII: Symptoms, signs, and abnormal clinical and laboratory findings, not elsewhere classified', and 'Chapter XXI: Codes for special purposes', with a median LOS of three days.

Bivariate analysis revealed significant association between age and type of primary reason for admission as shown in Table 1. Although chi-square test for association between type of primary diagnosis and the three LOS categories showed no significant association (χ2²= 2.931, p-value = 0.231), further binary logistic regression performed to ascertain the effects of reasons for admission using ICD-10 chapters on the likelihood that participants had LLOS, with G20 as the reference point was statistically significant, χ2(4) = 53.072, p<0.001. Despite the model was only able to explain 7.7% (Nagelkerke R2) of the variance in reasons for admission, it was able to correctly classify 91.7% of cases (Table 4).

Of the available category, only four were statistically significant, which were shown in Table 4; 'Chapter I: Certain infectious and parasitic disease' (OR = 4.19, CI95%: [1.22, 2.47]), 'Chapter V: Mental and behavioral disorders' (OR = 6.29, CI95%: [2.40, 16.5]), 'Chapter XII: Diseases of the skin and subcutaneous tissue' (OR = 3.58, CI95%: [1.37, 9.35]),  and 'Chapter XIX: Injury, poisoning and certain other consequences of external cause' (OR = 3.15, CI95%: [1.26, 7.89]), which had 4, 6, 3.5- and 2.5-times higher odds, respectively to be hospitalised longer than median LOS of 18 days (LLOS), compared to G20. 

 DISCUSSION

To the best of our knowledge, this is the first study to determine the primary diagnosis and length of hospital stay of PwP in Malaysia. Despite the fact that the PwP characteristics examined in this study are limited to gender and age group, the findings are consistent with those of other studies (Paul et al. 2017; Zhao et al. 2011). However, the findings of the male predominance of PD contradict the result of a study in Russia that reported a higher proportion of females (62% compared to males) diagnosed with PD, which may be attributed to the study’s limited sample size (n=100) (von Campenhausen et al. 2011).

Our study also showed that the biggest contributor to the PwP inpatient admission was not due to the primary diagnosis of G20. Instead, 'Chapter X: Disease of the Respiratory System' was the commonest (19.2%) among hospitalised PwP, particularly the diagnosis of unspecified pneumonia (J18.90) and aspiration pneumonia (J69.0). This might be due to complications in PD progression such as multiple autonomic dysfunctions, including dysphagia, which increase the risk of aspiration and other types of respiratory infection (Paul et al. 2017). This echoed the finding of another study that reported 24% of their admissions were also due to the same disease category (Kelly et al. 2016). 'Chapter IX: Disease of the Circulatory System' was found to be the second-highest cause of PwP admission in the current study. Although the aetiology of how PD affects circulatory symptoms was not well established, PD was associated with a higher risk of developing cardiovascular diseases (Hong et al. 2021; Park et al. 2020). ‘Chapter XIX: Injury, poisoning, and certain other consequences of external causes' was the third major cause of admission. 

Further investigation revealed that closed fracture of the neck of the femur (S72.00) was the primary contributor for the chapter, accounting for 1.5% of total admissions. The risk of falls is a well-known area of concern in the PD population. Research demonstrates 2.6 to 4.4-fold risk of sustaining fractures of the proximal femur in PD populations compared to age-matched controls (Kelly et al. 2016; Kleiner et al. 2018).

Meanwhile, ‘Chapter I: Certain infections and parasitic diseases' was the disease with the longest median LOS in this study, contributed mainly by sepsis (A41.9). This can be explained by multi-modality management of the patient with sepsis, including optimisation of antibiotic administration, depending on severity and type of infection (Busch & Kadri 2020). ‘Chapter XII: Diseases of skin and subcutaneous tissue has a median LOS of nine days, which was the second-longest category in our study together with ‘Chapter V: Mental and behavioural disorders'. As patients progressively become disabled, their mobility will be limited too. Prolonged immobility may lead to chronic pressure on the skin, leading to cellulitis and pressure ulcers, which take a long time to heal. Furthermore, skin disorders, which can be a non-motor symptom of PD and skin-related effects of dopaminergic medication, may worsen the conditions (Skorvanek & Bhatia 2017). Complicated management of PwP with mental and behavioural disorders contributed to the prolonged LOS. Patients need to be properly well and stabilised before discharge to reduce the caregiver’s burden at home and reduce frequent emergency department visits.

Limited information on PwP’s sociodemographic factors was one of the limitations of our study as it could help in further understanding other PwP populations. The study also made use of publicly available data; while these data provided valuable information, patient misclassification or coding errors cannot be ruled out. On the contrary, the large sample size used in this study may contribute to the high level of statistical significance observed in many comparisons.

CONCLUSION

In conclusion, the majority of PwP admissions in HCTM from 2010 to 2020 were not directly PD related. The LOS of non-G20 primary diagnoses was generally longer than that of G20 primary diagnoses. Therefore, it is important to make extra efforts to recognise PD complications earlier before they worsen and require hospitalisation which can save a lot of hospital resources. The caregivers should be educated regarding potential infections so that the infections can be detected earlier and managed in outpatient settings. Potential causes of injury, especially due to falls, should also be taken care of, by enhancing safety features in their living home. In addition, a guidance for caregiver should also be developed to assist them in managing a PwP at home.

Acknowledgement

The authors wish to acknowledge their gratitude to the Research Ethics Committee of the National University of Malaysia for approval of this study. (UKM PPI/111/8/jep-2021-342). The authors did not receive any funding for this study.