Parkinson's disease (PD) is a neurodegenerative disease characterized by bradykinesia, rigidity, and resting tremors. Although nigrostriatal dopaminergic degeneration is a major pathological hallmark that results in motor dysfunction in PD, it is well known that various central nervous systems and peripheral autonomic nervous systems are widely affected in PD. For example, constipation and olfactory dysfunction usually precede the onset of motor dysfunction in PD [1]. In an advanced stage of PD, cognitive dysfunctions and autonomic dysfunctions usually develop in addition to the development of motor dysfunctions. Among autonomic dysfunctions, lower urinary tract dysfunctions are prevalent and severe in an advanced stage of PD. There are many papers examining the prevalence and severity of lower urinary tract symptoms in PD, and it is well-known that both urinary storage and voiding symptoms are prevalent in PD [2]. However, the association between lower urinary tract symptoms and motor, cognitive, and health-related quality of life (HRQOL) is not well understood. We aimed to clarify the association between lower urinary tract symptoms and motor and cognitive functions, and HRQOL by performing multiple regression analysis.

We examined 34 PD (14 male patients and 20 female patients) patients who were admitted to our hospital to determine the indications for device-aided therapy such as deep brain stimulation. The mean age was 61.5±8.6 years and the mean disease duration was 11.7±3.0 years. The lower urinary tract symptoms and QOL was examined by International Prostate Symptom Score (IPSS) and IPSS-QOL, respectively. The motor symptoms and activities of daily living (ADL) were examined by Unified Parkinson's disease Rating Scale (UPDRS). The cognitive functions were examined by Mini-Mental State Examination (MMSE) and Frontal Assessment Battery (FAB). The HRQOL was examined by Parkinson's disease Questionnaire-39 (PDQ-39). We performed multiple regression analyses to determine which clinical parameters such as motor and cognitive functions, and HRQOL affect the lower urinary tract symptoms.

The score of IPSS had significant negative associations with the score of FAB (β=-0.391, p=0.031) and significantly positive associations with the score of UPDRS Part 2 (ADL) during an off phase (β=0.477, p=0.038). Because the higher FAB score represents better frontal lobe functions and the higher score of UPDRS Part 2 represents worse ADL, the present results suggested that better frontal lobe functions and preserved ADL during the off phase led to better lower urinary tract symptoms. The score of IPSS-QOL had significantly positive associations with the levodopa equivalent dose (dose of anti-parkinsonian drugs) (β=0.484, p=0.003) and the score of UPDRS Part 3 (motor functions) during the on phase (β=0.599, p=0.005). Because the higher score of UPDRS Part 3 represents the worse motor functions, better motor functions during the on phase and a lower dose of anti-parkinsonian drugs lead to better IPSS-QOL.

It is very reasonable that preserved ADL during the off phase led to better lower urinary tract symptoms because functional incontinence might be less prevalent in PD patients with relatively preserved ADL during the off phase. Furthermore, because previous reports suggested that detrusor contractility correlated with motor functions in PD patients, PD patients with preserved ADL might also have relatively preserved detrusor contractility leading to better lower urinary tract symptoms. It is also very important that better frontal lobe functions led to better lower urinary tract symptoms. Recent several imaging studies and experimental animal studies suggested that the frontal lobe has an important role in regulating voluntary micturition. The present result might indicate that examining frontal lobe function is important for the evaluation of lower urinary tract symptoms in PD patients.
Concerning the associations between IPSS-QOL and motor functions, it is also reasonable that relatively preserved motor function during the on phase led to better IPSS-QOL. Although the effect of anti-parkinsonian drugs on urinary functions is controversial, PD patients with a lower dose of anti-parkinsonian drugs usually have more preserved motor function, which might result in better IPSS-QOL.

Better frontal lobe functions and preserved ADL might lead to better lower urinary tract symptoms. Better motor functions during the on phase and lower doses of anti-parkinsonian drugs lead to better IPSS-QOL.

Schapira AHV, Chaudhuri KR, Jenner P. Non-motor features of Parkinson disease. Nat Rev Neurosci. 2017 Jul;18(7):435-450. doi: 10.1038/nrn.2017.62. Epub 2017 Jun 8. Erratum in: Nat Rev Neurosci. 2017 Aug;18(8):509. PMID: 28592904.
McDonald C, Winge K, Burn DJ. Lower urinary tract symptoms in Parkinson's disease: Prevalence, aetiology and management. Parkinsonism Relat Disord. 2017 Feb;35:8-16. doi: 10.1016/j.parkreldis.2016.10.024. Epub 2016 Nov 1. PMID: 27865667.