Does nephrotic syndrome without chronic kidney disease increase the risk of Parkinson’s disease and secondary parkinsonism? A nationwide population-based study in Taiwan

OBJECTIVES: Previous research has shown that patients with nephrotic syndrome (NS) have a higher risk of cognitive impairment, dementia or neurodegenerative disorder. The present study aimed to examine a relationship, if any exists between NS and Parkinson’s disease (PD), a neurodegenerative disorder and secondary parkinsonism (sPS). METHODS: A nationwide retrospective observational study conducted using data from the 2000–2010 Taiwan National Health Insurance Research Database. This study included 3663 patients with NS and 14 652 randomly selected, age-matched and sex-matched patients without NS. A Cox multivariable proportional hazards model was used to evaluate the risk of PD and sPS (PDsPS) in the NS cohort. RESULTS: This study identified a positive association between NS and the risk of PDsPS in both men and women and in all age groups (adjusted HR 1.51; 95% CI 1.37 to 1.66). Compared with patients without NS and comorbidities, those with NS with two or more comorbidities exhibited an 8.23-fold higher risk of PDsPS (95% CI 6.22 to 10.9) and patients with NS and one comorbidity exhibited a 2.93-fold higher risk of PDsPS (95% CI 2.37 to 3.63). CONCLUSIONS: Patients with NS have an increased risk of PDsPS. This increased risk may be related to brain vascular damage or blood–brain barrier impairment. Further research is necessary to explore the underlying relationship between NS and PDsPS.