Risk stratification for physical morbidity using factors associated with atypical antipsychotic treatment in Parkinson's disease: A retrospective observational study using administrative claims data.

Evidence shows that atypical antipsychotics (AAPs), a treatment of psychosis in Parkinson's disease (PD), are associated with factors reflecting the severity of the disease. Therefore, we evaluated the applicability of these factors in risk stratification for physical morbidity in PD patients requiring AAPs. We implemented a nested case-control analysis using administrative claims data derived from PD inpatients in 143 National Hospitals in Japan between April 2012 and March 2017. The analysis compared PD patients exposed to AAPs with unexposed matched controls using conditional logistic regression. The cases were then stratified by the weighted score using the partial regression coefficients of extracted factors or the number of factors that they had. Physical morbidity was evaluated using length of stay (LOS) and readmission. After comparing the cases (n = 829) with the matched controls (n = 3316), 10 factors were extracted. The cases were stratified into four level groups using the weighted score, or five level groups using the number of factors. LOS was prolonged with increasing score (49.7; 58.5; 72.7; and 83.3 days) and number of factors (52.1; 52.9; 63.9; 80.7; and 79.1 days). Readmission within 30 days increased along with increasing score (5.7; 10.2; 10.2 and 12.9%) and number of factors (5.9; 9.3; 8.9; 11.3; and 14.3%). We confirmed two stratification manners for physical morbidity in PD patients requiring AAPs. These manners would be useful for considering management plan for these patients.